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300 RUM barrel life. The whole documantation.

 
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Old 04-02-2009, 03:53 PM
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300 RUM barrel life. The whole documantation.

This post is to avoid any further hijacking of another thread.

Bear in mind I have had similar results in my first barrel. Not as pronounced and undocumented, but similar.

If you read the notes CAREFULLY and pay attention to the velocity readings AND the dates they were taken, you will see the message I am trying to convey.

I have compiled a write up of development and events as they occurred. After I received the rifle back from my smith, I gave her a good cleaning from the test firings and was amazed that there was absolutely NO copper to be removed. I got powder fouling out but no copper. The Rock barrel was living up to its reputation. I assumed this by using Sweets 7.62 solvent and not getting even the least amount of blue color. I didn’t get her complete and in my hands until late November of 2008

My development techniques involve never shooting more than 20 shots between cleanings. This allows for 2 foul shots and 6 different groups with various charges of the same powder and bullet. I NEVER shoot a load using a different powder without a thorough cleaning and fouling 2 shots. I also don’t mix bullets by brand or type. For example I don’t test 6 shots with a 178 AMAX and then run the 180 ACCUBOND even if I am using the same powder. I don’t think it would have mattered in the beginning due to the lack of copper fouling. I never have fired this barrel at any time more than 3 shots per group with the exception of one 5 shot group that was spaced out over more than a 10 minute period as I would fire a shot and drive down to the 300 yard mark to check for a reading on the chronograph for ballistic coefficient test. In no case has there been any bullets fired back to back in less than 30 seconds and I typically give her a bit more time between shot 2 and 3. All firings have been for developmental or test purposes. The round count keeps going up due to regular changes in load performance and the need to re-adjust the load.

Day one at the range

11-28-2008 After a simple break in routine, I began to test some loads. Both break in and first test loads were loaded with H50BMG powder due to past experiences with the 300 RUM with a custom barrel and match quality chamber. H50BMG offers less pressure with a full case for safe operation especially when I don’t know how things will react. The last 300 RUM barrel I had generated extremly high pressures. My only powder choice was H50BMG. 95.5 grains of it and the 200 AB gave me 3150 FPS. All other powders were loaded WAY under to keep it safe. It is for this reason that I started with H50BMG.

After seeing low velocities with the 50BMG powder (2893) I moved to a low dose of RL-25 under the 200 ACCUBOND. According to my notes a total of 16 rounds were fired during break in.

I never judge a rifle based on my first day at the range. There are too many mental distractions and hopes to really concentrate on the task at hand. However, there were 3 groups that showed signs of real promise and with excellent hunting bullets to boot! I was getting really excited. The very first group was right at 1 MOA. A couple of groups later it shot a .75 MOA group. The last group was just over 0.4 MOA.

Load notes:

The very first groups were with the 200 AB over H50BMG using 92, 93, 94 and 95 grains of H50BMG. Then I tried 93 and 95 grains of 50BMG and the 180 TSX. Velocity average for 95 and the 200 AB was 2885 FPS. 95 and the 180 TSX was 2963 FPS. The last group was 86.0 of RL-25 with the 200 AB.

Best load tested on day one.

86.0 RL-25 with the 200 ACCUBOND
Velocity 1: 2941, Velocity 2: 2916, Velocity 3: 2942
Accuracy = 0.4” @ 100 yards.

day two at the range

Day two was really exciting. I only fired 2 groups and went home. I only fired two because I shot the lowest charges I had and decided that if they weren’t max loads, they were max enough. The first group was .486” at 100 yards. The second group was .241”.

Load notes:

Load one: 91.0 RL-25 with the 200 ACCUBOND
Velocity 1: 3236, Velocity 2: 3177, Velocity 3: 3191
Accuracy = 0.486” @ 100 Yards. Perfect extraction, primers look good, no ejector marks.

Load two: 95.0 RL-25 with the 180 ACCUBOND
Velocity 1: 3412, Velocity 2: 3342, Velocity 3: 3377
Accuracy = 0.241” @ 100 Yards. Perfect extraction, primers look good, no ejector marks.
Note that these loads were fired on 11-29-08.

Day 3 at the range

I am not one to settle for high extreme spreads. Later I learned that my case necks were in need of annealing and that RL-25 actually gave me the lowest ES with proper neck tension. Never the less, I had to see what H1000 and RETUMBO would do.

Load notes:

Load one: 95.0 RETUMBO with the 180 ACCUBOND
Velocity 1: 3340, Velocity 2: 3315, Velocity 3: 3330
Accuracy = 0.656” @ 100 Yards. No pressure signs.

Load two: 91.0 H1000 with the 180 ACCUBOND
Velocity 1: 3144, Velocity 2: 3154, Velocity 3: 3135
Accuracy = 0.6” @ 100 Yards.

One week later. First 300 yard session

It was time to move on from 100 yards to 300 yards. The first 300 yard group was promising but not great.

Load notes:

Load one: 95.0 H1000 with the 180 ACCUBOND
Velocity 1: 3276, Velocity 2: 3255, Velocity 3: 3279
Accuracy = 2.293” @ 300 Yards.
It should be noted that these velocities were read on 12-3-2008 and extraction was perfect with no marks on the brass

Load two: 96.0 RETUMBO with the 180 ACCUBOND
Velocity 1: 3351, Velocity 2: 3352, Velocity 3: 3375
Accuracy = 3” @ 300 Yards.

Second 300 yard session

It was now time to re-test the best load. Prior to this session there was a total of 62 excluding break in rounds but includes all foul shots after cleaning.



Load notes:

Load one: 95.0 RL-25 with the 180 ACCUBOND
Velocity 1: 3485, Note that the bolt was stuck and had to be tapped open. There was a major extractor mark and cratered primer. Velocity 2: 3437, note that extraction was easier but sticky. Extractor mark as well. Velocity 3: 3395, note that the extraction was easier yet but still a bit sticky.
Accuracy = just over 3 inches @ 300 Yards.

Load two: 96.0 H1000 with the 180 ACCUBOND
Velocity 1: 3345, Velocity 2: 3316, Velocity 3: 3301
Accuracy = 2.155” @ 300 Yards.

Load three: 96.5 H-1000 with the 180 ACCUBOND
Velocity 1: 3373, Velocity 2: 3344, Velocity 3: 3380
Accuracy = 2.082” @ 300 Yards.
It is noted that this load was hot due to slightly sticky extraction and ejector marks.

Load four: 90.0 H-1000 with the 180 E-Tip
Velocity 1: 3238, Velocity 2: 3227, Velocity 3: 3218
Accuracy = 3” @ 300 Yards.
Load was reduced by 5 grains initially for fear the pressure would be too high with the same charge of powder using bullets of the same weight of a softer construction.
Note that the four loads above were fired on 12-6-2008

On 12-7-08 I fouled 2 shots using RL25 and 180 E-tips. After the foul shots I fired 2 E-tips at 300 yards. The 3rd was not fired due to sticky extractions and very poor accuracy. After another cleaning and fouling, I tested another load that showed promise in the recent past. This was the 180 ACCUBOND using 95.0 of H1000. The previous highest velocity just a few days prior was 3279 with no extraction issues. On the 7th the velocities were as follows: 1: 3367, 2: 3362 and 3: 3355 FPS. Almost a full 100 FPS faster and was noted that the load was a bit hot with semi sticky extraction and some marks on the brass. Other notable changes documented are on 12-14-08 I had reduced the 180 AB load from 95.0 of RL25 to 92.0 at 3377, 3360 and 3395 FPS. Still a bit warm so the load was reduced further. The last time this load was tested the charge was dropped to 90 grains and the bullet was changed to the 178 AMAX. This bullet doesn’t seem to generate as much pressure as the 180 AB. The velocities are right at the 3300 mark with no extraction trouble or brass issues. Also I went from 91 of RL25 to 88 grains of RL25 and the velocities were 3177, 3194 and 3174 with the 200 AB. Now it doesn’t matter what powder or charge weight is used. The 180 AB and the 200 AB particularly the 200 AB will NOT offer easy extraction and is very hard on the brass. On day one 95 grains of 50BMG yielded 2885 FPS average and the last time I tried the same load it was 3150 FPS. That test marked the last of my lot of BMG powder. All other powders used in this rifle have been from the same lot as well as primers and brass. This is by far the most extreme instance of rising pressure thus far. The last time I tried the 200 AB was just a couple of weeks ago (mid March) using 86.0 RL25 and the primer pockets were very loose and the base had bad extractor marks on them. I was not able to get velocity readings for this session. Accuracy was also very bad. The 200 AB’s will not group at all anymore.

This certainly does not mark the end of the development and testing but it shows you a pattern of rising pressure from day to day. I do not exactly remember when it started to copper foul but it was around the 80 to 80+ count. It was noticeable at first and over the next 100 shots or so became very bad. To date the round count in this Rock barrel is 427 +/- a handful of foul shots not documented towards the recent past.

I took my barrel to a local smith the other day (around the 15th of March) along with the old Lilja barrel I still have that has over 1000 rounds through her. I compared the throat of each side by side as well as several inches up the barrel. The Rock looks almost identical to the Lilja. At this point, it become clear as to why it copper fouls so bad now and won’t shoot the same as it did in the beginning with the same loads. I only had between 60-65 shots through it when I noticed the major changes. The throat may have been somewhat cooked already at that point.

Most notable loads currently (not in order)

84.0 RL-25 with the 180 TSX. Just over 3200 FPS with good accuracy.

89.0 RL-25 with the 190 HORNADY BTSP. Just over 3250 FPS with good accuracy.

93.0 H50BMG with the 208 AMAX. Started at 2925 FPS with the new lot of powder and is currently 2975 FPS with good accuracy. Accuracy has dropped a bit recently.

90.0 H50BMG with the 220 SMK. 2850 FPS with good accuracy. Have not tested recently.

In conclusion, all in all it has shown accuracy potential better than expected it just wouldn’t duplicate any good results from day to day presumably due to the rapid internal changes. After the first couple hundred shots when things “settled” down the changes still happen just not nearly as fast. What took a few days and a few shots now takes 50 to over 50 shots over a couple weeks or more to really notice a change in velocity and accuracy. I kept shooting it because I dont feel satisfied with where it is going to be from day to day and was trying to get her to settle down some more. Now that I have had a smith look at it and seeing what I saw through the hawkeye, I have stopped all shooting of it.

I hope the load notes here make a bit more sense as to why I started with such low velocity. Also since I had such low velocity loads in the beggining, they are still safe to shoot today for testing purposes. This is how I know that the velocity is up nearly 300 FPS.

2 barrels of similar quality. Same chamber similar results. The fact is the 300 RUM cartridge is hard on barrels. So hard, it CAN change the way your loads react throughout the life of the barrel.

In Rocks defense, he offered to look at the barrel and replace it if the metal is faulty. It is in the mail as we speak. However, given the fact that A, I am not the only shooter that has these results and B, another barrel of another reputable brand showed the same issues, I highly doubt it will get a new barrel from Rock.

Regards.
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Last edited by Michael Eichele; 04-02-2009 at 04:16 PM.
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Old 04-02-2009, 08:20 PM
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Re: 300 RUM barrel life. The whole documantation.

Hi Mick,

Interesting results!

I am not sure what to make of it though. I always assumed that pressures would drop as throat erosion got worse and the bullet got a longer jump to the rifling. This seems to be working the other way about?

One thought I have is that you may be getting all the copper out when you are cleaning your barrels but maybe there is still a build up of carbon "powder glaze" taking place in the throat area?

Have you tried giving it a scrub with JB bore cleaning paste to pollish up the throat area? My smith recomends doing this at the 200, 400 and 2000 shot period.
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Old 04-02-2009, 08:40 PM
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Re: 300 RUM barrel life. The whole documantation.

Quote:
Originally Posted by Topshot View Post
I am not sure what to make of it though. I always assumed that pressures would drop as throat erosion got worse and the bullet got a longer jump to the rifling. This seems to be working the other way about?
According to Mike Rock, as a throat deteriorates it creates friction. The more it deteriorates, the more friction it causes, the more friction it cause, the higher the pressure spike early on.


Quote:
Originally Posted by Topshot View Post
One thought I have is that you may be getting all the copper out when you are cleaning your barrels but maybe there is still a build up of carbon "powder glaze" taking place in the throat area?

Have you tried giving it a scrub with JB bore cleaning paste to pollish up the throat area? My smith recomends doing this at the 200, 400 and 2000 shot period.

I dont use JB anymore. When the solvents come out in the same color they went in I stop.
__________________
Long range shooting is a process that ends with a result. Once you start to focus on the result (where the shot goes, how big the group is, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.
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Old 04-04-2009, 07:53 AM
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Re: 300 RUM barrel life. The whole documantation.

I disagree with your generalized statment:

"The fact is the 300 RUM cartridge is hard on barrels. So hard, it CAN change the way your loads react throughout the life of the barrel."

I have a 27" SS Lilja in 300 RUM that has 468 rounds through it and it never showed the pressure problems you have had. As a matter of fact we would hear plenty of stories from others with even worse over bore calibers if this sort of issue was common. I had a factory 7 RUM that I shot the heck out of without issues.

You never mentioned your cleaning procedure nor did you mention what you saw with the borescope. I will admit you were quite thorough with your loading and testing.

My conclusion? Seeing you are no longer shooting it, JB the hell out of it before you ship it back to Rock. I'd bet you would find you have a closed up bore due to carbon buildup which is giving you the higher velocities and pressures. You should be able to push a tight patch through before using JB and then afterwards and feel the difference.

If you do this let us know what you discover.
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Old 04-04-2009, 12:43 PM
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Re: 300 RUM barrel life. The whole documantation.

What I saw through the bore scope was heat cracks galore and a VERY cooked throat. It looked simialr to my Lilja barrel with over 1000 rounds in her.

I also said it CAN change the way a load reacts not that it WILL change the way a load reacts. To believe that it CANNOT is very close minded.
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Long range shooting is a process that ends with a result. Once you start to focus on the result (where the shot goes, how big the group is, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.
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Old 04-04-2009, 05:15 PM
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Re: 300 RUM barrel life. The whole documantation.

Hi again,

Didn't mean to offend you. I was just stating that I haven't heard of the 300 RUM ruining a barrel that quickly. Now that you mentioned the condition of the interior of the barrel I am changing my opinion. It is not a partially obstructed bore it is burned out way ahead of schedule.

I would imagine if you sent your documentation and the barrel it would be hard to argue that there is something wrong with the quality of the steel. Best of luck on a new barrel. Just curious would you make another 300 RUM?
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Old 04-04-2009, 06:11 PM
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Re: 300 RUM barrel life. The whole documantation.

No offense taken. I am going to wait and see what the manufacturer finds berfore i decide to do anthing.
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Long range shooting is a process that ends with a result. Once you start to focus on the result (where the shot goes, how big the group is, what your buck will score, what your match score is, what place you are in...) then you loose the capacity to focus on the process.
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