Finished a customers 338 Allen Magnum XHS Repeater this week and decided I wanted to do a complete load development using the new Bertram brass. Since Jamison International stopped making my custom 338 AM brass, I have had to switch to Bertram brass. This is not a bad thing as this brass is actually a better match to my reamer specs and has proven to be a bit stronger then the Jamison brass.
How much stronger I really did not know as I had not done a real complete load work up with the new brass to find its limits, until this morning. First off, a bit of gun porn.
I did the velocity testing at the shop using the 300 gr berger Hybrid bullet and H-50BMG lit with a Fed-215 primer. OAL for the ammo was 4.280". My standard "accuracy" load for the 338 Allen Magnum is 142.0 gr H-50BMG and 3270 fps when loaded in the old Jamison cases. Max load in the Jamison cases was generally in the 3320 fps range with acceptable case life, that being at least 6 firings per case.
In the new cases I started at this level and worked up until the primer pockets let loose. Again, the top loads listed are for education purposes only, I am in no way recommending loading any 338 Allen Magnum to levels higher then the loads I list as max working load. Here are the results:
142.0 gr.........................3264 fps
143.0 gr.........................3292 fps
144.0 gr.........................3316 fps
145.0 gr.........................3358 fps choosen test load
146.0 gr.........................3384 fps
147.0 gr.........................3427 fps Max working load (Faint ejector ring)
148.0 gr.........................3445 fps (slight ejector ring on case head)
149.0 gr.........................3461 fps (heavy ejector ring on case head)
150.0 gr.........................3483 fps (loosening primer pocket)
In the end of the testing, the 145.0 gr load (3358 fps) resulted a load that allowed 6 firings on a single case with more firings left in the case. After 6 firings, the primer pocket had loosened noticeably but there was still plenty of resistance when seating a primer in the case and there was no gas leakage of any kind. I am sure this load will allow 8 firings per case, very similar to the accuracy load in the Jamison cases but roughly 100 fps more velocity with same case life.
I decided this would be the load I tested for accuracy in this customers rifle so I headed up to the range. By the time I got to the range the temp had increased from 60 degrees which it had been at the shop to roughly 84 degrees on the range. I wanted to stretch this big rifle out so I decided to set up at 1790 yards. Bore sighted the rifle and took a few shots to get the point of impact close to the point of aim.
I set up the video camera and let the barrel cool down. Then fired a three shot group at this range. The first and second shot landed pretty much on top of each other, the third shot landed around 1 1/4 moa to the right. Not uncommon to get a few fliers as the fresh rifles settling in.
Let the barrel cool and fired another three shot group. This one was much better measuring just over 3/4 moa. Very good.
Let the barrel cool and then fired the last three shot group out of the rifle. Prior to this group I made a scope adjustment but the wind had shifted abit and fooled me. Missed the target rock by a couple moa but these three shots easily went into a 1/2 moa group. If someone can tell me how to upload a video made on a Windows Live Movie maker program to Youtube, Facebook or Photobucket, please fill me in and I will share the video of the last group with all. Pretty happy with the rifle and very happy with that last group. Looks like she will be a serious shooter.
With the new Bertram brass, it looks like the 338 Allen Magnum is able to get back very close to the original performance using the TTI brass. This new Bertram brass is very close to the strength of the old TTI brass and nearly identical in dimensions so it matches my reamers much better then the Jamison brass which had slightly thicker case necks.
Anyway, one more ready to fly to a new home. Onto the next round!!!!