Peterson 300 WM - Std Length vs. Long - Initial Data & Impressions

badthirtyone

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Peterson 300 Win Mag brass - Standard Length vs. Long - Initial Data & Impressions

Introduction


This thread is being generated for a number of reasons, not the least of which is in relation to the comments and questions that have come up during the multiple active threads regarding the release and availability of this brass in both "Standard" and "Long" variations. I felt it would also be appropriate to post additional information, presented as a fairly objective side-by-side comparison of both versions of this brass as I am fortunate enough to have several hundred unfired, virgin cartridge cases of each on hand to conduct this initial testing as well as long-term/lifespan testing.

The 300 Win Mag is still one of the most prevalent and lethal big-game chamberings ever created, and is well thought of by the majority of the members of this forum, as well as by shooters from around the world. Because of the sheer popularity of this cartridge amongst the shooters here, it was an easy fit to write this evaluation and comparison for these pages and fellow members.

I will state up-front that while I am a considerable Peterson Cartridge fan due to my personal history in dealing with - and in loading their brass for a number of years, I am not directly affiliated with, sponsored by, or being compensated by Peterson Cartridge. I fully paid for (and waited patiently for) these casings to arrive for my own personal use.

I will also - strongly state - that I am not an expert. I do not claim to be, nor have I ever considered myself one. I am simply a shooter, an intermediate reloader, and probably, more than I'd like to admit, an "average" hunter. (Lookin' at you, Bean & FEENIX).

If you'd like to skip directly to my collected data, scroll to the bottom third of this post.

Brief History of the introduction of the 300 WM's from Peterson

In the summer of 2020, July 20th - per their press release - Peterson introduced the 300 Win Mag to their lineup, followed immediately by the release of the "Long" version for this chambering.

The "Standard" version is exactly that. It is manufactured, as 300 WM cases have been manufactured since this caliber's introduction in 1963 (based on its parent case, the .338 Win Mag - introduced in 1958, & the .375 H&H Magnum - introduced in 1912). The Peterson standard length cases fire-form to their respective chambers, requiring the brass to flow and elongate to fill the space between the virgin casing and the chamber shoulder-wall. This results in brass movement that could lead to premature fatigue due to what Peterson considered unnecessary elongation that could be eliminated if the cases were simply manufactured much closer to the final fire-formed dimensions. Enter the "Long" version of the Peterson 300 WM that is made to more closely fit and fill a standard SAAMI spec'd chamber - in its virgin state, right out of the box.

(See Peterson news release https://www.petersoncartridge.com/technical-articles/posts/2020/august/peterson-got-the-belt/)
(See also - Long release https://www.petersoncartridge.com/t...terson-cartridge-introduces-300-win-mag-long/)

While I am quite aware that I am posting on a highly educated & experienced forum, directed at what should be highly educated and experienced shooters - I'll note here that these "Long" cases are fully engineered and meant for any firearm chambered in 300 Win Mag. These are not some specialty cases meant for custom reamed long-chambers, but rather brass meant for "regular" 300 WM chambers - that will hopefully outlive other cases based on not needing to stretch and flow near as much, especially during the first firing.

One of the things that I greatly respect about the development of the 300 WM's at Peterson, was their refusal to release these to the shooting public until they had worked out the issues surrounding the belt, and the associated problems that belted cartridge manufacturing entails. Through their press releases, as well as speaking to employees directly at Peterson, they would not release any "belted" cases until they could produce a "world-class" version of this brass.

While a handful of competitive shooters and "evaluation" shooters began to receive and test these cases in the late summer of 2020, they became available on a more broad level during the fall, and into Christmas of that year.

The release of this brass appeared to be complicated by several factors, not the least of which was that it was a highly anticipated addition to what had been so-far, the phenomenal success of the entire Peterson lineup of brass products. It was regularly, and still is, as of the time of this writing, sold-out and difficult to get without spending months on a waiting list.

The release was also greatly complicated by the wide-spread effects of the Covid-19 virus and it's resulting decimation of almost all shooting related items, as well as limiting the number of employees available/allowed to work at multiple points in the supply-chain that led to additional wait times simply to have a product shipped, even if it was in stock. Most of these issues appear to be receding as of the time of this writing but low stock on both standard and long versions continue to persist due to sheer demand.

I was fortunate enough to be in the "right place at the right time" around Thanksgiving of 2020, and was able to secure several hundred of the "Standard" length cases. Having said that, I will be honest in that I was also not being exceptionally patient, so I ordered the standards which were available, knowing that I may have to wait several months to get my hands on the even harder to find "Long" version of this brass. Ultimately, I waited just over a month to receive my "Standards" in January of 2021, and recently received my "Longs" in mid-August of this year.

Initial Impressions

So far, I have been genuinely impressed with ALL of the various cartridge cases that I have received from Peterson - in all of the calibers that I have tried them in. Overall, both versions of this brass have arrived - in what I have come to expect from Peterson - wonderfully and carefully packaged, and in excellent condition.

All of the cases, from both lots appear to be uniform and free of visible defects. I generally inspect each of my cases both inside (with a flashlight) and out, and have found none that needed to be culled during this initial visual inspection.

IMG_0312a.jpg

Shown here are the variations & lot numbers of the brass used for this evaluation

*I do appreciate the quality of the plastic cases and standard packaging employed by Peterson

IMG_0313 combo.jpg

Visually, all cases of both "Standard" (left) and "Long" (right), were consistent and appear to be defect-free


IMG_0316a.jpg

Thoughtful head-stamping that distinguishes the
"Long" version (top) from its standard kin (bot)


*I'll note that any dissimilarity in the appearance of the brass in the above photo is due to lighting, and not due to inconsistencies in condition or quality of the cases. It's just difficult to photograph head-stamps together for a clear shot. ;)


_____________________________________________________________________________________________________________________________________________________________________________

Tools and Testing

While the cases appeared to be consistent and defect free, I am a stickler for data-driven testing and evaluation, so cases were put through various dimensional and capacity tests in a side-by-side, systematic process.

In regards to the questions from other forum members about the differences in the two versions of these cases, as well as my own personal desire to get this information, I will be testing the following:
  1. Length - raw, OAL of unfired cases
  2. Differences in Base-to-shoulder dimensions - utilizing two methods, 1- Hornady Base to Shoulder Comparator, & 2 - LE Wilson Mic die
  3. Weight - raw, base weight of empty, unprimed case
  4. Weight - plugged and filled with water by pipette
  5. Derivation of capacity of H2O
  6. Analysis and comparison to data published by Peterson - supplied for these exact cases and lot numbers
* A note on methodology and information collected:

I chose 10 random samples from each Lot# and length version for this testing. I believe that 10 examples of each version (Std & Long) results in quality data points, and a high degree of confidence in the measurements taken. All brass was tested in as-is condition, right out of the box, with no prep work or modification of any kind.

While I strive to accurately collect data on all sorts of important components and measurements required by "precision" reloaders, I'll clarify that the information that I collected during these specific tests was for Comparison between the cases, not to be taken as "hard" or stand-alone measurements. That is to say that I was most interested in the differences between the two versions of the Peterson 300 WM cases, so the data I collected demonstrates those differences.

This becomes critical because, while my comparators are set at known distances and diameters for my use, they would be of little use to other reloaders that have different comparators. This is the quandary/unfortunate reality discussed at length by Brian Litz (available from multiple sources, and predominantly featured on pages 153 & 154 of Berger's 1st Ed reloading manual) regarding general inconsistencies and non-uniform measuring devices designed to capture "comparator" information. This is most dramatically seen on Base-to-Ogive measurements that become useless when EXACT data is transferred between shooters. The simple answer is that your Base-to-Ogive measurement will vary from mine, because you are using a different comparator that is not exactly like mine.

Having said all of that, I believe that the data collected during these tests are exceptionally useful - because they are compared directly to data collected on the different versions of these cases utilizing the same equipment.

It is for the realities mentioned above that I do not concern myself with actual Base-to-Shoulder measurements, but only in getting precise results in the differences in those measurements between the various sample cases.

Along those lines, it is also important to point out that I utilize a particular method of water capacity testing that I am very fond of, due to its repeatability and ease of use, that may be nominally different than your, or Peterson's, or Brian Litz' method. I have found that my method of capacity testing is generally within 1% of published results, by people that actually do claim to be experts. For example, in my analysis below, my results for the capacity tests of the "Longs," my recorded numbers are .0089 (0.89%) of what Peterson has published for the exact lot number of brass in question.

Bottom line is that I have confidence in my data, and your ability to derive useful results from it.

If you are still with me, continue on to the testing and analysis! 😁




Below are the collected tools for the testing mentioned.

Length & Base to Shoulder measurement
IMG_0321 combo.jpg

LE Wilson Mic die and Head-space gauge
Gauge is currently set for the rifle - Remington 700P - that will fire the finished rounds

IMG_0325a.jpg

Hornady Base to shoulder comparator

*Results shown in data table represent comparison information, not corrected measurements - see note above on methodology

Water Capacity Testing
IMG_0330.JPG


Water Capacity testing plug
IMG_0331a.jpg

For H2O capacity testing, I utilize a disassembled and cleaned primer that
acts as a quality primer hole plug. It gets fully seated, by RCBS hand primer
then de-capped and moved to the next case. I also take an additional tare
weight of each case which includes the weight of this plug prior to filling -
See column on data table below - "Weight + plug"


_____________________________________________________________________________________________________________________________________________________________________________


The Data

The following data was collected utilizing the above mentioned process. This data represents information collected during my "hands-on" testing of these cases

PBA 300 data sorted.PNG


Peterson Data

The following data was pulled directly from publicly available data that you can get from the Peterson website. They keep incredible, and useful information - by Lot#. Notice the inclusion of the AMP Aztec codes provided for each lot and date of mfg. This is super information for reloaders who do not want to destroy a "sacrificial case" during AMP analysis. Find your Lot# and run them!

Peterson data sorted.PNG


Analysis - Useful information

Lessons learned and observations on data collected

  1. Length - I was surprised to see that my testing revealed that the "Long" cases were actually, on average .0023" shorter than the "Standard" cases in regards to Overall Length. I do not believe this to be detrimental in any way, but it was an unexpected data point.
  2. Variations within Lot #'s - While the variations I observed were marginal and should not affect performance, I noticed that the "Standard" cases were nearly identical in Overall Length, but varied more in Hornady Comp & Wilson Mic testing, whereas the "Long" cases varied more in Overall Length, but were indistinguishably identical in Hornady Comp & Wilson Mic testing.
  3. Base to Shoulder comparison - In utilizing two distinct and separate methods of measuring this difference, I captured measurements of .0118" with the Hornady Comparator, along with .0116" with the LE Wilson Mic head and Head-space gauge. this is an overall difference of only .0002" between the methods employed. This also gives a quantitative result of just under .012" of difference between the Std & Long cases from base to shoulder.
  4. Water Capacity - Testing resulted in an average of 89.17 gr for the Std cases, and 89.70 gr for the Long - resulting in a difference of +.56 gr in the Long
  5. Comparison to Peterson data - While they do not provide data by specific Lot# regarding lengths, the data available in H2O capacity was certainly validating to my own testing, as their published data shows a capacity difference between the two lots in question at .6 grains compared to my results of a .56 gr difference.
So, what now?

While there was a half grain increase in water capacity in the "Long" cases, translating to a greater powder capacity, this increase should only be beneficial or noticeable on the first firing. After all, fire-formed cases will be dramatically closer to equal capacity regardless of starting length version. I'll test this to verify once I have several fire-formed examples of each version, but I'm leaning toward them evening out quite a bit in overall capacity.

While I believe that there are marked benefits of the new "Long" cases, especially in longevity/case life, I also fully believe that the "Standard" cases will continue to perform wonderfully if properly prepped and cared for. In fact, I'm already on my third loading of many of the standard cases that I received in January of this year. In regards to those 3 firings, I'm generally in the .4 MOA range for the Berger VLD's I've been working up. Hoping to improve upon that, but for a hunting gun, I'm already happy and moving in the right direction.

Continued testing will be conducted and documented so that the "hoped for" results of longer case life out of the "Long" cases can be seen. For this continued side-by-side comparison, all cases will be prepped, cleaned, annealed, sized, trimmed in as close to an identical manner as possible. this should provide an objective apples-to-apples comparison over their lifespan.

Feel free to reach out to me with any questions or comments.

badthirtyone





Below, I have included the text of the press release from Peterson regarding their motivation and efforts resulting in the creation of this new brass in 300 WM "Long." The link to this article (also posted above in this thread) is on their website is: https://www.petersoncartridge.com/t...terson-cartridge-introduces-300-win-mag-long/
_____________________________________________________________________________________________________________________________________________________________________________

Peterson Cartridge introduces .300 Win Mag – Long

Pittsburgh, PA (July 20, 2020) – Peterson Cartridge Co. of Pittsburgh, PA announced it is producing .300 Win Mag casings in two versions. Peterson makes the traditional SAAMI spec’d version that headspaces off the belt. But it also makes a version that headspaces off the shoulder. Peterson calls that version the .300 Win Mag- Long.



Shooters that reload .300 Win Mag casings have often wished they could get more reloads from their casings. Well now you can!

Derek Peterson, president of Peterson Cartridge explains, “Traditional .300 Win Mag casings tend to show signs of case head separation after only 5 to 7 firings.

“Here’s why. The SAAMI specs for any caliber, list a minimum and a maximum tolerance for each dimension on the casing and the rifle’s chamber. With most calibers, the max dimension of the casing, for length-to-shoulder (L-T-S), has the shoulder of the casing right up against the chamber wall. With .300 Win Mag, unlike most other calibers, if your rifle’s chamber is cut to the SAAMI minimum for L-T-S, and your casing is at the max length-to-shoulder dimension, the casing shoulder is still .0095” away from the chamber wall. With the same minimum rifle chamber, a casing at nominal L-T-S is .012” away from the chamber wall. In a worst-case scenario, if the casing was produced at the SAAMI minimum L-T-S, and the chamber was cut at the maximum L-T-S dimension, the casing shoulder could be up to .026” away from the chamber wall. That might not sound like a lot, but it is.

“That large gap is what causes the casing to stretch so much when it is fired. It’s that stretching that causes premature case head separation.”

Peterson continued, “With Peterson .300 Win Mag- Long casings, we make them with a longer L-T-S dimension. All the other dimensions are SAAMI spec. But the longer L-T-S prevents the casing from stretching excessively on the 1st firing. The casing has more support, which translates to less stretching, which translates to longer case life.”


Peterson concluded, “If you are a handloader, that wants more reloads from your .300 Win Mag casings, we think you will appreciate our new .300 Win Mag - Long casings. I’d like it if you’d give them a try and let us know what you think.”

About Peterson Cartridge

Peterson Cartridge is a family-owned, American manufacturer of match-grade, brass rifle casings and loaded ammunition that is among the most precise and consistent on the market, delivering discerning long-distance shooters sub-MOA accuracy. For more information on Peterson Cartridge or to purchase its match-grade brass casings, or loaded ammunition, visit www.petersoncartridge.com.
 

DerekPeterson

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This is Derek Peterson over at Peterson Cartridge. I want to say thank you for spending the time to collect all of this data. I am glad to see that our Ballistician Testing Data matches your findings. I will let our Ballistician, Stan, know that his work isn't going unnoticed. If you ever need anything, please feel free to reach out to our customer service line at 724-940-7552. Zack will be happy to help you out.
 

badthirtyone

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LRH Team Member
Joined
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Messages
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Location
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This is Derek Peterson over at Peterson Cartridge. I want to say thank you for spending the time to collect all of this data. I am glad to see that our Ballistician Testing Data matches your findings. I will let our Ballistician, Stan, know that his work isn't going unnoticed. If you ever need anything, please feel free to reach out to our customer service line at 724-940-7552. Zack will be happy to help you out.

Wow! That was an unexpected response, to say the least!

Thank you for the kind words and for your respect of the above analysis. Please let your team know that the overall community of shooters - at least those that actually care about getting the absolute most out of their hand loads and other equipment - genuinely appreciate all of the work that your team does and your apparent pursuit of excellence.

I’m glad you now have a presence on this forum, and have an opportunity to interact with the outstanding shooters that utilize your products.

I feel honored to be the first member here to say - Welcome to the forum!
 
Last edited:

ShtrRdy

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High Plains
Wow!! Thanks for putting this together!! I was thinking I would get some Lapua in 300 Win Mag at some point but the Peterson brass sounds really nice.

Can you comment on how the flash holes look on the I side of the case?

Sounds like you shoot the 300 Win Mag quite a bit.
 

badthirtyone

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LRH Team Member
Joined
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Messages
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Location
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Wow!! Thanks for putting this together!! I was thinking I would get some Lapua in 300 Win Mag at some point but the Peterson brass sounds really nice.

Can you comment on how the flash holes look on the I side of the case?

Sounds like you shoot the 300 Win Mag quite a bit.
ShtrRdy,

I'll say that I load for a current total of 7 rifle cartridges, and 6 handgun cartridges - feeding a total of more overall guns than I care to mention... ;)

I do spend a good amount of time, especially over the past 2 years, behind a 300 Win Mag. It has always been a love of mine and is the single cartridge/caliber that is responsible for putting more deer and elk in my freezer over the past 25 years than all other cartridges combined. While I have always enjoyed hunting with a 300 WM, these past couple of years I have also become more of a 300 shooter for general range days & distance work.

I'll also say that I have loaded almost all of what the membership here (and on any other forum) would consider to be "premium" brass in most every caliber that I load for. Over the past few years I have almost exclusively limited my personal brass purchases to Lapua and Peterson and I consider them both to be the cream of the crop. Having said that, I'll also note that I really do love the advancements that Peterson has made in the shooting world - and their innovation with products like the 300 WM Long cases. I really think you'd be well-served by these cases if you are going to up your 300 shooting game.

As to the condition of the flash holes, they are centered, concentric, and from what I can tell through a thoughtful examination of the inside - I do not plan on deburring the interior, although I wouldn't hold it against anyone who does for the ultimate in consistency.

Hope this helps!
 

john k

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Joined
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Messages
268
Location
North Central FL
This is Derek Peterson over at Peterson Cartridge. I want to say thank you for spending the time to collect all of this data. I am glad to see that our Ballistician Testing Data matches your findings. I will let our Ballistician, Stan, know that his work isn't going unnoticed. If you ever need anything, please feel free to reach out to our customer service line at 724-940-7552. Zack will be happy to help you out.
X2 on data. Very interesting and useful. I’ve been waiting for quite awhile as others on .280 Ackley Improved brass. Will it be available this year? I don’t think I have heard a negative review or comment on Peterson brass. Thanks
 

john k

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Peterson 300 Win Mag brass - Standard Length vs. Long - Initial Data & Impressions

Introduction


This thread is being generated for a number of reasons, not the least of which is in relation to the comments and questions that have come up during the multiple active threads regarding the release and availability of this brass in both "Standard" and "Long" variations. I felt it would also be appropriate to post additional information, presented as a fairly objective side-by-side comparison of both versions of this brass as I am fortunate enough to have several hundred unfired, virgin cartridge cases of each on hand to conduct this initial testing as well as long-term/lifespan testing.

The 300 Win Mag is still one of the most prevalent and lethal big-game chamberings ever created, and is well thought of by the majority of the members of this forum, as well as by shooters from around the world. Because of the sheer popularity of this cartridge amongst the shooters here, it was an easy fit to write this evaluation and comparison for these pages and fellow members.

I will state up-front that while I am a considerable Peterson Cartridge fan due to my personal history in dealing with - and in loading their brass for a number of years, I am not directly affiliated with, sponsored by, or being compensated by Peterson Cartridge. I fully paid for (and waited patiently for) these casings to arrive for my own personal use.

I will also - strongly state - that I am not an expert. I do not claim to be, nor have I ever considered myself one. I am simply a shooter, an intermediate reloader, and probably, more than I'd like to admit, an "average" hunter. (Lookin' at you, Bean & FEENIX).

If you'd like to skip directly to my collected data, scroll to the bottom third of this post.

Brief History of the introduction of the 300 WM's from Peterson

In the summer of 2020, July 20th - per their press release - Peterson introduced the 300 Win Mag to their lineup, followed immediately by the release of the "Long" version for this chambering.

The "Standard" version is exactly that. It is manufactured, as 300 WM cases have been manufactured since this caliber's introduction in 1963 (based on its parent case, the .338 Win Mag - introduced in 1958, & the .375 H&H Magnum - introduced in 1912). The Peterson standard length cases fire-form to their respective chambers, requiring the brass to flow and elongate to fill the space between the virgin casing and the chamber shoulder-wall. This results in brass movement that could lead to premature fatigue due to what Peterson considered unnecessary elongation that could be eliminated if the cases were simply manufactured much closer to the final fire-formed dimensions. Enter the "Long" version of the Peterson 300 WM that is made to more closely fit and fill a standard SAAMI spec'd chamber - in its virgin state, right out of the box.

(See Peterson news release https://www.petersoncartridge.com/technical-articles/posts/2020/august/peterson-got-the-belt/)
(See also - Long release https://www.petersoncartridge.com/t...terson-cartridge-introduces-300-win-mag-long/)

While I am quite aware that I am posting on a highly educated & experienced forum, directed at what should be highly educated and experienced shooters - I'll note here that these "Long" cases are fully engineered and meant for any firearm chambered in 300 Win Mag. These are not some specialty cases meant for custom reamed long-chambers, but rather brass meant for "regular" 300 WM chambers - that will hopefully outlive other cases based on not needing to stretch and flow near as much, especially during the first firing.

One of the things that I greatly respect about the development of the 300 WM's at Peterson, was their refusal to release these to the shooting public until they had worked out the issues surrounding the belt, and the associated problems that belted cartridge manufacturing entails. Through their press releases, as well as speaking to employees directly at Peterson, they would not release any "belted" cases until they could produce a "world-class" version of this brass.

While a handful of competitive shooters and "evaluation" shooters began to receive and test these cases in the late summer of 2020, they became available on a more broad level during the fall, and into Christmas of that year.

The release of this brass appeared to be complicated by several factors, not the least of which was that it was a highly anticipated addition to what had been so-far, the phenomenal success of the entire Peterson lineup of brass products. It was regularly, and still is, as of the time of this writing, sold-out and difficult to get without spending months on a waiting list.

The release was also greatly complicated by the wide-spread effects of the Covid-19 virus and it's resulting decimation of almost all shooting related items, as well as limiting the number of employees available/allowed to work at multiple points in the supply-chain that led to additional wait times simply to have a product shipped, even if it was in stock. Most of these issues appear to be receding as of the time of this writing but low stock on both standard and long versions continue to persist due to sheer demand.

I was fortunate enough to be in the "right place at the right time" around Thanksgiving of 2020, and was able to secure several hundred of the "Standard" length cases. Having said that, I will be honest in that I was also not being exceptionally patient, so I ordered the standards which were available, knowing that I may have to wait several months to get my hands on the even harder to find "Long" version of this brass. Ultimately, I waited just over a month to receive my "Standards" in January of 2021, and recently received my "Longs" in mid-August of this year.

Initial Impressions

So far, I have been genuinely impressed with ALL of the various cartridge cases that I have received from Peterson - in all of the calibers that I have tried them in. Overall, both versions of this brass have arrived - in what I have come to expect from Peterson - wonderfully and carefully packaged, and in excellent condition.

All of the cases, from both lots appear to be uniform and free of visible defects. I generally inspect each of my cases both inside (with a flashlight) and out, and have found none that needed to be culled during this initial visual inspection.

View attachment 293638
Shown here are the variations & lot numbers of the brass used for this evaluation

*I do appreciate the quality of the plastic cases and standard packaging employed by Peterson

View attachment 293664
Visually, all cases of both "Standard" (left) and "Long" (right), were consistent and appear to be defect-free


View attachment 293650
Thoughtful head-stamping that distinguishes the
"Long" version (top) from its standard kin (bot)


*I'll note that any dissimilarity in the appearance of the brass in the above photo is due to lighting, and not due to inconsistencies in condition or quality of the cases. It's just difficult to photograph head-stamps together for a clear shot. ;)


_____________________________________________________________________________________________________________________________________________________________________________

Tools and Testing

While the cases appeared to be consistent and defect free, I am a stickler for data-driven testing and evaluation, so cases were put through various dimensional and capacity tests in a side-by-side, systematic process.

In regards to the questions from other forum members about the differences in the two versions of these cases, as well as my own personal desire to get this information, I will be testing the following:
  1. Length - raw, OAL of unfired cases
  2. Differences in Base-to-shoulder dimensions - utilizing two methods, 1- Hornady Base to Shoulder Comparator, & 2 - LE Wilson Mic die
  3. Weight - raw, base weight of empty, unprimed case
  4. Weight - plugged and filled with water by pipette
  5. Derivation of capacity of H2O
  6. Analysis and comparison to data published by Peterson - supplied for these exact cases and lot numbers
* A note on methodology and information collected:

I chose 10 random samples from each Lot# and length version for this testing. I believe that 10 examples of each version (Std & Long) results in quality data points, and a high degree of confidence in the measurements taken. All brass was tested in as-is condition, right out of the box, with no prep work or modification of any kind.

While I strive to accurately collect data on all sorts of important components and measurements required by "precision" reloaders, I'll clarify that the information that I collected during these specific tests was for Comparison between the cases, not to be taken as "hard" or stand-alone measurements. That is to say that I was most interested in the differences between the two versions of the Peterson 300 WM cases, so the data I collected demonstrates those differences.

This becomes critical because, while my comparators are set at known distances and diameters for my use, they would be of little use to other reloaders that have different comparators. This is the quandary/unfortunate reality discussed at length by Brian Litz (available from multiple sources, and predominantly featured on pages 153 & 154 of Berger's 1st Ed reloading manual) regarding general inconsistencies and non-uniform measuring devices designed to capture "comparator" information. This is most dramatically seen on Base-to-Ogive measurements that become useless when EXACT data is transferred between shooters. The simple answer is that your Base-to-Ogive measurement will vary from mine, because you are using a different comparator that is not exactly like mine.

Having said all of that, I believe that the data collected during these tests are exceptionally useful - because they are compared directly to data collected on the different versions of these cases utilizing the same equipment.

It is for the realities mentioned above that I do not concern myself with actual Base-to-Shoulder measurements, but only in getting precise results in the differences in those measurements between the various sample cases.

Along those lines, it is also important to point out that I utilize a particular method of water capacity testing that I am very fond of, due to its repeatability and ease of use, that may be nominally different than your, or Peterson's, or Brian Litz' method. I have found that my method of capacity testing is generally within 1% of published results, by people that actually do claim to be experts. For example, in my analysis below, my results for the capacity tests of the "Longs," my recorded numbers are .0089 (0.89%) of what Peterson has published for the exact lot number of brass in question.

Bottom line is that I have confidence in my data, and your ability to derive useful results from it.

If you are still with me, continue on to the testing and analysis! 😁




Below are the collected tools for the testing mentioned.

Length & Base to Shoulder measurement
View attachment 293665
LE Wilson Mic die and Head-space gauge
Gauge is currently set for the rifle - Remington 700P - that will fire the finished rounds

View attachment 293655
Hornady Base to shoulder comparator

*Results shown in data table represent comparison information, not corrected measurements - see note above on methodology

Water Capacity Testing
View attachment 293656

Water Capacity testing plug
View attachment 293657
For H2O capacity testing, I utilize a disassembled and cleaned primer that
acts as a quality primer hole plug. It gets fully seated, by RCBS hand primer
then de-capped and moved to the next case. I also take an additional tare
weight of each case which includes the weight of this plug prior to filling -
See column on data table below - "Weight + plug"


_____________________________________________________________________________________________________________________________________________________________________________


The Data

The following data was collected utilizing the above mentioned process. This data represents information collected during my "hands-on" testing of these cases

View attachment 293662

Peterson Data

The following data was pulled directly from publicly available data that you can get from the Peterson website. They keep incredible, and useful information - by Lot#. Notice the inclusion of the AMP Aztec codes provided for each lot and date of mfg. This is super information for reloaders who do not want to destroy a "sacrificial case" during AMP analysis. Find your Lot# and run them!

View attachment 293666

Analysis - Useful information

Lessons learned and observations on data collected

  1. Length - I was surprised to see that my testing revealed that the "Long" cases were actually, on average .0023" shorter than the "Standard" cases in regards to Overall Length. I do not believe this to be detrimental in any way, but it was an unexpected data point.
  2. Variations within Lot #'s - While the variations I observed were marginal and should not affect performance, I noticed that the "Standard" cases were nearly identical in Overall Length, but varied more in Hornady Comp & Wilson Mic testing, whereas the "Long" cases varied more in Overall Length, but were indistinguishably identical in Hornady Comp & Wilson Mic testing.
  3. Base to Shoulder comparison - In utilizing two distinct and separate methods of measuring this difference, I captured measurements of .0118" with the Hornady Comparator, along with .0116" with the LE Wilson Mic head and Head-space gauge. this is an overall difference of only .0002" between the methods employed. This also gives a quantitative result of just under .012" of difference between the Std & Long cases from base to shoulder.
  4. Water Capacity - Testing resulted in an average of 89.17 gr for the Std cases, and 89.70 gr for the Long - resulting in a difference of +.56 gr in the Long
  5. Comparison to Peterson data - While they do not provide data by specific Lot# regarding lengths, the data available in H2O capacity was certainly validating to my own testing, as their published data shows a capacity difference between the two lots in question at .6 grains compared to my results of a .56 gr difference.
So, what now?

While there was a half grain increase in water capacity in the "Long" cases, translating to a greater powder capacity, this increase should only be beneficial or noticeable on the first firing. After all, fire-formed cases will be dramatically closer to equal capacity regardless of starting length version. I'll test this to verify once I have several fire-formed examples of each version, but I'm leaning toward them evening out quite a bit in overall capacity.

While I believe that there are marked benefits of the new "Long" cases, especially in longevity/case life, I also fully believe that the "Standard" cases will continue to perform wonderfully if properly prepped and cared for. In fact, I'm already on my third loading of many of the standard cases that I received in January of this year. In regards to those 3 firings, I'm generally in the .4 MOA range for the Berger VLD's I've been working up. Hoping to improve upon that, but for a hunting gun, I'm already happy and moving in the right direction.

Continued testing will be conducted and documented so that the "hoped for" results of longer case life out of the "Long" cases can be seen. For this continued side-by-side comparison, all cases will be prepped, cleaned, annealed, sized, trimmed in as close to an identical manner as possible. this should provide an objective apples-to-apples comparison over their lifespan.

Feel free to reach out to me with any questions or comments.

badthirtyone





Below, I have included the text of the press release from Peterson regarding their motivation and efforts resulting in the creation of this new brass in 300 WM "Long." The link to this article (also posted above in this thread) is on their website is: https://www.petersoncartridge.com/t...terson-cartridge-introduces-300-win-mag-long/
_____________________________________________________________________________________________________________________________________________________________________________

Peterson Cartridge introduces .300 Win Mag – Long

Pittsburgh, PA (July 20, 2020) – Peterson Cartridge Co. of Pittsburgh, PA announced it is producing .300 Win Mag casings in two versions. Peterson makes the traditional SAAMI spec’d version that headspaces off the belt. But it also makes a version that headspaces off the shoulder. Peterson calls that version the .300 Win Mag- Long.



Shooters that reload .300 Win Mag casings have often wished they could get more reloads from their casings. Well now you can!

Derek Peterson, president of Peterson Cartridge explains, “Traditional .300 Win Mag casings tend to show signs of case head separation after only 5 to 7 firings.

“Here’s why. The SAAMI specs for any caliber, list a minimum and a maximum tolerance for each dimension on the casing and the rifle’s chamber. With most calibers, the max dimension of the casing, for length-to-shoulder (L-T-S), has the shoulder of the casing right up against the chamber wall. With .300 Win Mag, unlike most other calibers, if your rifle’s chamber is cut to the SAAMI minimum for L-T-S, and your casing is at the max length-to-shoulder dimension, the casing shoulder is still .0095” away from the chamber wall. With the same minimum rifle chamber, a casing at nominal L-T-S is .012” away from the chamber wall. In a worst-case scenario, if the casing was produced at the SAAMI minimum L-T-S, and the chamber was cut at the maximum L-T-S dimension, the casing shoulder could be up to .026” away from the chamber wall. That might not sound like a lot, but it is.

“That large gap is what causes the casing to stretch so much when it is fired. It’s that stretching that causes premature case head separation.”

Peterson continued, “With Peterson .300 Win Mag- Long casings, we make them with a longer L-T-S dimension. All the other dimensions are SAAMI spec. But the longer L-T-S prevents the casing from stretching excessively on the 1st firing. The casing has more support, which translates to less stretching, which translates to longer case life.”


Peterson concluded, “If you are a handloader, that wants more reloads from your .300 Win Mag casings, we think you will appreciate our new .300 Win Mag - Long casings. I’d like it if you’d give them a try and let us know what you think.”

About Peterson Cartridge

Peterson Cartridge is a family-owned, American manufacturer of match-grade, brass rifle casings and loaded ammunition that is among the most precise and consistent on the market, delivering discerning long-distance shooters sub-MOA accuracy. For more information on Peterson Cartridge or to purchase its match-grade brass casings, or loaded ammunition, visit www.petersoncartridge.com.
Great info and data. Thanks for taking the time and energy posting this article. I do not shoot a .300 WM but always a big fan.
 

Don Titus

Well-Known Member
Joined
Jan 11, 2013
Messages
161
Location
PA
Excellent and thorough reporting! Thank you for your efforts. I have a 300WM project in the offing. I'm gonna start with the "longs"!
Thank you for your thorough reporting. I have been a Peterson believer for several years after using their cases for my .308 Winchester. I too have been waiting for their 300 WM cases and was fortunate to purchase 100 short cases in June.
As a Pennsylvanian, I am proud of Peterson and their outstanding products..,👍
 

QuietTexan

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Nov 16, 2020
Messages
731
Location
Fort Worth, Texas
Very nice write up. Quick question on methodology - is there a benefit to using the primer to plug the case versus something like the 21st Century plugs? They are ~$25 each, but to me the ease of use is worth it.

I would like it if Grafs sold 6.5-284 in 250 case lots like you were able to get, 500 cases is a bit excessive for that cartridge and essentially the same per-case cost as 300 Win Mag.
 

badthirtyone

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LRH Team Member
Joined
Nov 26, 2007
Messages
764
Location
Denver Colorado
Very nice write up. Quick question on methodology - is there a benefit to using the primer to plug the case versus something like the 21st Century plugs? They are ~$25 each, but to me the ease of use is worth it.

I would like it if Grafs sold 6.5-284 in 250 case lots like you were able to get, 500 cases is a bit excessive for that cartridge and essentially the same per-case cost as 300 Win Mag.
#1 - Thanks

#2 - I have tried several methods of plugging the primer hole for H2O capacity testing and found that using the disassembled & cleaned primer cup to be about the cheapest, most repeatable, and stupid-simple method available. More than anything, everyone of us has tons laying around, you know that they will more than adequately plug the hole and - if you mess one up or damage it, you have 1000 extra to work with.

I know full well that there are tons of other options for plugging the hole, and I am not knocking any of them. I just go with the one that works exceptionally well for me.

#3 - I would agree that most calibers should be available in 50's, 250's & 500 piece quantities and I'm not sure why they chose which cartridges to sell at any given quantity. At least it is cool that they offer more than a simple 50 piece option for reloaders looking to get "bulk qty" numbers. I feel for you though, it can be an investment - to say the least.
 

Muddyboots

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Feb 7, 2013
Messages
3,392
Location
Michigan
One heck of a detailed thoughtful analysis of the Peterson brass. Like I told @badthirtyone, "Speak with data" and everything is just noise. I have one load lot at 3X firings and primer pockets are still nice and firm. This is a 196HH @3150 with RL26 so it is a stout load just under pressure. I am so thankful I bought 250 Long brass when I did since I am certain not likely to find now that the word is out.😂

I have found it to be really good brass at reasonable pricing. The subsequent fire form cases are really "true" to your chamber and I have really not had to do much to prep the brass all that much for next load. The overall case growth is minimal in my experience. If you have a chance to try, suggest doing so.

Oh yeah, the 196HH is very accurate load!
 
Last edited:

Mike from Texas

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Joined
Sep 7, 2013
Messages
551
Location
North Texas
I’ve been very happy with all Peterson brass that I have used. Very consistent and seems to be tough as I push all my cartridges hard.
I have 50 pieces of the long brass and look forward to trying it out as well.
 

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