Most brass too short. Trim them all?

[entoptics]

Greetings. First post, but I've gleaned lots of info over the years. Great forums.

Summary:

My 300 win mag brass is averaging well below the trim-to length. Should I trim it all to near the shortest and go for it, or should I waste a bunch and try and cull out the stuff that's well below 2.610"?

Details:

1) I'm already on my second barrel for this rifle (Savage LRH 300 Win), and burned up the first doing all sorts of experiments (and shooting for fun). The rifle averages about 1 MOA out to 1000 yds, but seems to do a bit better here and there.

2) I'm tired of dinking around, and want to put a pile of ammo on the shelf. There's only two things I want to address before I load up 300 rounds. Concentricity (gauges arrive tomorrow), and brass OAL. I doubt my groups will change much, but eliminating those variables is a "better safe than sorry" sort of thing I don't mind addressing.

3) Awhile back I bought new MAI (Lapua) brass, and it all arrived too short (≤2.610") from the get go. I think the average was down around 2.600". Other than that, it was phenomenally good for the price (~$0.75 each) and has worked well. I've now got almost all of it cycled through my gun at least once, but even the 2X fired stuff is barely reaching 2.610".

4) I don't want to waste more time/barrel/money shooting just to "grow" my brass till it all can be trimmed to match. I also don't want to cull out a bunch and waste the half that's too short.

What's your opinions on trimming everything a bit short (2.606" probably), so it's all the same at least? I know I could do the experiment myself, but putting another 100+ rounds down range, to get the statistics to find out, just isn't in the cards.

 

[vinson]

2.6" is the saami min for 300 win mag. I say don't worry about it.

 

[Lonewolf74]

I wouldn't worry about trimming them. Chances are your actual chamber length is .050-.070 over the 2.620 book max length (typical of saami 300wm chambers).

My 300 is this way (I measured with a plug seated in a modified case) so I trim once to 2.620 when the brass has grown past that point to square and uniform case mouths then I don't trim again (unless brass grows to 2.670 which it will probably get scrapped before that happens). So with this rifle i have brass measuring from 2.610 to 2.640 and it all shoots the same and is a consistent sub 1/4 moa.

 

[AZShooter]

IMO unless the brass is getting close to the end of the chamber I see no reason for any of it to be trimmed.

My approach is to measure the end of the chamber and measure the brass after every sizing to see how the brass compares to that value. If it gets close I trim. Some chambers are so long the brass will be worn out before it stretches enough to be trimmed. I have some very accurate rifles and don't trim them to match in length even after a dozen firings unless necessary.

Sinclair has a chamber length gauge for measuring the end of the chamber:

https://www.sinclairintl.com/reload...s/sinclair-chamber-length-gage-prod32925.aspx

video:


I doubt you will see any difference in downrange performance from a sporter rifle with slightly varying case lengths. You could do a control and shoot the pet load with the shortest and the longest brass and compare results.

If you see a difference please post back here and share.

 

[105amatt]

I would leave it alone. I doubt there would be any noticeable change in group size, especially in a 300wm. It's not like you're shooting bench rest sized groups with that cannon. Well, at least i don't with mine.

 

[J E Custom]

Greetings. First post, but I've gleaned lots of info over the years. Great forums.

Summary:

My 300 win mag brass is averaging well below the trim-to length. Should I trim it all to near the shortest and go for it, or should I waste a bunch and try and cull out the stuff that's well below 2.610"?

Details:

1) I'm already on my second barrel for this rifle (Savage LRH 300 Win), and burned up the first doing all sorts of experiments (and shooting for fun). The rifle averages about 1 MOA out to 1000 yds, but seems to do a bit better here and there.

2) I'm tired of dinking around, and want to put a pile of ammo on the shelf. There's only two things I want to address before I load up 300 rounds. Concentricity (gauges arrive tomorrow), and brass OAL. I doubt my groups will change much, but eliminating those variables is a "better safe than sorry" sort of thing I don't mind addressing.

3) Awhile back I bought new MAI (Lapua) brass, and it all arrived too short (≤2.610") from the get go. I think the average was down around 2.600". Other than that, it was phenomenally good for the price (~$0.75 each) and has worked well. I've now got almost all of it cycled through my gun at least once, but even the 2X fired stuff is barely reaching 2.610".

4) I don't want to waste more time/barrel/money shooting just to "grow" my brass till it all can be trimmed to match. I also don't want to cull out a bunch and waste the half that's too short.

What's your opinions on trimming everything a bit short (2.606" probably), so it's all the same at least? I know I could do the experiment myself, but putting another 100+ rounds down range, to get the statistics to find out, just isn't in the cards.

Max SAMME length is 2.620. All brass normally will be less than Max length because not all chambers are that long.

Ideally, brass should be .010 to .020 shorter than the chamber. If you know what your chamber actually it as long as your brass is shorter you are ok. If the brass is not slightly shorter than the chamber, there will/ may be pressure problems.

It is not unusual for cases to be trimmed .040 shorter than the chamber for rapid fire matches where fouling can stop the function of the weapon.

There is an ideal trim length for each chamber and use. Then there a practical trim length and it can be significantly different.

My recommendation would be that you trim all 300 that pieces to the same length and go from there. This will give you the best consistency, and longevity of your brass. Also as you shoot it you can check to see how much growth you are getting with your loading and make adjustments if need be. Remember growth means thinning. the more growth, the more thinning. This is one reason I am an advocate of sizing only as much as necessary so the brass does not have to grow very much to fit the chamber each time it is fired.

J E CUSTOM

 

[Mikecr]

Should I trim it all to near the shortest?

NO
There is no reason to trim them all too short.

 

[JTB]

I would trim them all to the same length and continue to trim them as needed to maintain that brass OAL for that rifle. You probably won't notice a difference at first but unless you clean the barrel often a carbon ring may begin to form in the throat where the shorter length case mouth ends and cause pressure spikes when the longer cases are chambered over that ring. I had this happen to me years ago and finally solved the problem by keeping all brass for that barrel trimmed to the same length. That carbon ring can be a pain to remove.

 

[Mikecr]

That carbon ring is caused by several things -including too much end clearance.
It is so often that our fixes are also the causes of what we try to fix.
Classic tail chasing..

 

[cape cove]

That carbon ring is caused by several things -including too much end clearance.
It is so often that our fixes are also the causes of what we try to fix.
Classic tail chasing..

Once you know your chamber length how much shorter do you recommend keeping the cases. TKS

 

[entoptics]

Seems like I'm getting some mixed messages here...

Perhaps a clarifying question will help.

How much gain/loss in accuracy could be expected from 0.01 case OAL variance (2.615 to 2.605) vs 0.001 variation in freshly trimmed, but SHORT cases that are all the same at 2.605"?

I might have one more shooting day before I have to get to reloading, so I may be able to do a statistically dubious experiment by shooting a couple of small groups to test. The problem is finding 10 brass with a wide range of neck lengths, but no other variation (i.e. weight), and 10 brass with the same short neck length, but no other variation either. Not to mention, seeing a small precision variation with only a handful of rounds is probably not likely.

Lastly...Before the "hunting rifle accuracy" and "good enough" comes up, I understand that all this prep won't turn a 1.5 MOA gun into a 0.5 MOA gun.

That being said, I'm willing to do the work, and sort of enjoy it, so it's worth it to me for...

1) for peace of mind (best possible ammo = fewer variables). If I know my ammo is good, I can't make excuses for my trigger finger, optics, wind calls, etc.

2) If doing it right would shave 1/8th MOA, I'd consider it time well spent. I like to shoot small things far away. For perspective a 1.125 MOA rifle has a deer-vital sized group (9.0") at 765 yds. A 1 MOA rifle is grouping the same at 860 yds.

 

[J E Custom]

The reason I would/do recommend trimming to the same length is for consistency. Also I would do it before any re loading/testing begins.

I would agree that you may not be able to see any accuracy change from one length to another "BUT" while working up you load difference in bullet tension/grip and sizing could make a difference and lower SDs even if only by 1 or 2 numbers and eliminate or minimize the differences in the neck tension and surface area of the neck.

I believe it is always best to make every component as consistent as possible when re loading ammo. I also recommend and faithfully turn all Of my necks before they are loaded the first time, so they are very true and consistent once they have been fire formed the first time.

Once you find the best combination for your loads, you may decide that some part of this procedure is not necessary for the accuracy required but at least you know what the potential of your rifle is with near perfect loading. If you can load ammo that will reduce group size from 1 1/2 MOA to 1 MOA you have improved your accuracy by 33.3 %. If you can reduce a .075 thousandth group to .050 thousandths, That's only .025 thousandths but it is still an improvement of 33.3 % and well worth it to me.

Turning and trimming also aides in concentricity testing loaded ammo.

Leave no stone unturned

J E CUSTOM

 

[entoptics]

...I also recommend and faithfully turn all Of my necks before they are loaded the first time, so they are very true and consistent once they have been fire formed the first time...

Once you find the best combination for your loads...

Leave no stone unturned

J E CUSTOM

I agree, and have done all of the following, over 2.5 years and ≥ 2000 rounds of personally loaded ammo in this rifle alone, BEFORE arriving at my original question about necks...

1) Started with Federal once fired match brass (and some mixed misc.), overcooked everything, and blew up a good bit of it after 2-3 firings. Replaced barrel at around 1300 rounds of 4000 ftlb fire breathers.

2) Cooled my jets, and did all of the standard testing of powder/bullet/length combos AGAIN with new barrel, using MAI (Lapua made) brass. Neck turned to 0.013" ± 0.0005. I weight sort and such too. I'm about 350 rounds into those experiments.

3) I've arrived at 208 ELDM (~0.7 - 1.2 MOA) and 212 ELDX (0.9 - 1.5 MOA). These are going right around 2850 (26" bbl) over H1000.

4) Learned I'm not a good enough shooter to go much below 1 MOA (not "this one time", I mean 7 outa 10 groups) with this rifle, or any other rifle I shoot regularly. I only ever shoot bipod and rear bag, prone, in a wheat field. I'm good with that.

Need to move on to other projects, and just pull this rifle out every month or two. Hit a 2 MOA target every time out to 1000 yds (and shoot a refrigerator at a mile once before I die).

Was hoping there's some statistics, formulas, experience regarding neck length. Last thing I'm trying to address...

 

[cgarb]

Learned I'm not a good enough shooter to go much below 1 MOA

I can't see how you can get good data to make decisions on case trim length shooting prone off Bipods in a wheat field. Not trying to ruffle your feathers but there are people here that shoot .25MOA rifles telling you it's not a big deal just load them. Admitting that your a 1MOA shooter off Bipods is admirable because most people luck out a .25 minuet group one day and then transform into a record breaking distance shooter overnight...lol. I know how tough it is to get under 1MOA off Bipods. My 308 will get under .5MOA off the bench, but off Bipods when I'm shooting a lot more like .75 to 1 MOA. I'm sure I could do better with practice, but I lack the time to shoot often. I wouldn't waste the time trimming myself if they are already short, even if there was a .0035" group improvement. My shooting abilities would never show it anyway.