Short Stroking in Subsonic AR15

[RobRat]

Checked my TP555 gas block, mine is (going clockwise) closed, then partially open, then fully open. Talked to the 'smith that installed it, he didn't remember the size of the port, but he says he drilled it to the size that the gas block came with. He's a real particular machinst, I doubt that he has it misaligned, but I may pull it and check if some further attempts don't pan out.

I tried lightening the rifle buffer - started at a stock weight of 5.2 oz, and dropped it to 4.5 oz by removing 2 of the weights and replacing them with a bronze bushing. Going to try taking more out.

I ran out of 240's and could only find 200's locally.

Tried 3 local gunshops, no one has AA1680, and the shop I ordered a pound from hasn't been to the distributor to pick it up yet, but should happen soon.

In the meantime, I'm trying some H4198 with the 200 gr smk's. Anyone tried H4198 in their Whisper? I've loaded 10 test loads (3 each) from 11.0 to 14.6 gr, stepping by 0.4gr. H4198 is #58 on the burn chart, AA1680 is #54, and VN120 is #59, so it should be in the ball park. I heard powder crunching when seating with the 14.2 and 14.6 loads.

[RobRat]

Tried the H4198 under the 200SMK's - and it cycled wonderfully! The slower powder is doing the trick, If I can only get some AA1680!!!

The range was crowded, and I was only able to set the chrono up for 4 of the loads, and shoot 3 of each.
11.0 gr averaged 857 fps
11.4 gr averaged 925 fps
11.8 gr averaged 1017 fps

I was able to chrono one other load - 13.0 gr, and it was supersonic with an average of 1183 fps

Because of the range situation I was not able to both test accuracy, and velocity at the same time, but I wasn not impressed with the accuracy of the loads I did shoot at targets - they were good horizontally, but at 50 yards had an inch and a half of horizontal.

[ezed]

i read your initial post and had exactly the same problem that you did with several loads last weekend. My whisper is set up pretty much like yours. The load that funtioned perfectly in mine, was 11.7 gr of 1680. average velocity for 17 shots was 1018 ft/s. outdoor temp 32 degrees
aa9 8.7 gr same as you described
aa9 9.1 gr same as you described
h110 9.6 gr same as you described
i will try more loads but this worked for me. email me if you want more complete data.
have fun!!

[ezed]

I just tested 4 different loads last weekend thru my 10.5 whisper.
220 gr smk
tp555 gas block subsonic position pistol position
gas port .115
Gemtech Sandstorm suppressor
ambient temp 32 deg
I had the same problem as you did with three different loads: extraction great, ejection great, reset the hammer but would not pick up and put a round back in the chamber. Pulled the trigger and the hammer would fall, but....
Loads that did not work:
AA 9 9.0 gr average velocity 1101
AA 9 8.7 gr average velocity 1022
H110 9.6 gr average velocity 1044
The load that worked and cycled perfectly:
AA 1680 11.7 gr average velocity 1018
email me if you would like complete data and information. I have each load on an excel spreadsheet.
I saw that someone posted a load for H322 somewhere, but cannot find that information. I figured that could be a good load cuz it makes a carbine work. Ok, strange, but, what the heck. Why not try it? Anybody have a load for 322?