243 AI-Any Input?

[BigDog00]

Thanks for the detailed write up. The comment about the standard chamber vs AI was interesting and something I have been considering. My load right now is pushing a 108ELDM just over 3000fps with H1000 in a 24" barrel, so I'd likely be around the 2900 as well cut down to 20". Lack of trimming would be cool, not sure if it's worth the extra work of an AI. Seems like if a guy was going to do the extra work why not chase the extra speed with a SAUM/PRC wildcat. All things to consider.

 

[PathFinder]

Thanks for the detailed write up. The comment about the standard chamber vs AI was interesting and something I have been considering. My load right now is pushing a 108ELDM just over 3000fps with H1000 in a 24" barrel, so I'd likely be around the 2900 as well cut down to 20". Lack of trimming would be cool, not sure if it's worth the extra work of an AI. Seems like if a guy was going to do the extra work why not chase the extra speed with a SAUM/PRC wildcat. All things to consider.

How many grains of H1000 is that load? The load I'm using now is 47.7 grains. Went quite a bit higher, but got clickers and even an ejector mark on the Alpha brass.

 

[BigDog00]

How many grains of H1000 is that load? The load I'm using now is 47.7 grains. Went quite a bit higher, but got clickers and even an ejector mark on the Alpha brass.

49.3 in virgin Starline brass got me 3014 fps across 10 shots.

 

[PathFinder]

After finally purchasing a proper chronograph (replaced a glitchy Magnetospeed with an Athlon), it was time to work up to speed/pressure again. I need matching head stamp brass for an upcoming Africa trip, so the test was conducted with both Federal and Alpha brass that were previously fire formed. Alpha brass had 4-5 firings on them, Federal had one past the initial fire form. The barrel had 526 rounds down it at the beginning of this test.
I've attempted to fire form Winchester brass in the past, but about 50% of them rupture at the shoulders. They are significantly lighter, and I assume the thinner walls are what prevent them from successfully forming. Federal weigh about the same as Alpha, so hopefully they form more successfully. Components were H1000, CCI 200, and a 116 TMK. COAL of 2.920.
As always, work up, but these are the charges and velocities:

Alpha:
49: No data. ~2900 est. Had the chrony too low.
49.5: 2929
50: 3000
50.5: 3003

Federal:
49: 2886
49.5: 2913
50: 2919
50.5: 2987

No significant pressure signs from any of the loads above. No heavy bolt lift, ejector marks, or clickers. The Alpha brass, on their 2nd and 3rd firings, were prone to clickers above 48 grains. This was only a few rounds, but now on their 4th-5th firings that problem didn't resurface. The bolt lift was somewhat lighter on the Federal brass. Overall very promising, and more in line with the target velocities for this round. Targeting 3k fps in either brass is looking really good right now.

Also fire formed six more Federal brass to see how they'd hold up. All six formed successfully with 39 gr H100V and a 105 Hybrid at 2880 fps. I want to research different brass (especially Starline) to see which others might be prone to successful fire forming. There will be a separate thread to collect data, but adding brass weights here would be helpful.

Alpha: ~176 grains
Federal: ~175 grains
Winchester: ~160 grains