Quote:
Originally Posted by CptCurl
I believe my OAL was too long, and that this caused the two failures to fully feed. It appeared to be binding slightly as the cartridge made the corner around the feed ramp going into the chamber. In my next tryout loads I will reduce the OAL to 1.115" Curl
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Curl,
The two jams you describe above sound like the typical, annoying "Luger Jam".
Cartridge O.A.L. is critical for positive action function. Your tests for proper O.A.L. should be done before you go the range. For a good explanation of how to determine proper O.A.L., for a new bullet type, please see my thread on "Determining Proper Cartridge O.A.L." in this section of the site. I bet your O.A.L. is too short, but you won't know until you have gone through the pre-firing development stage, then the range test. The original O.A.L.s, of both the 9mm and 7.65mm DWM truncated cone bullets, were right at 1.14 inches (29mm). I have noted that the wider the "flat" on the nose of the bullet, the shorter the proper O.A.L. for proper function. Remembering that the original DWM "flat" was 4mm, you might want to measure the "flat" on your subject bullet. If I were testing, I'd start at 1.15 inches and work down .01 inch at a time until I found perfect function.
Once you have determined the proper O.A.L., for the bullet you are testing, then you are free to move on to the charge development stage. Again, I'd start at about 4.8 grains, or so, of your SR 4756 and work up 0.1 of a grain, at a time, until you get perfect action function and accuracy. Accuracy, for me, is three out of three touching at 25 yards, shot over sand bags.
When the action starts working (with proper hold open) and the groups start tightening, then you are in the range to develop a great load.
I'd be interested in seeing the necks of your fired cases. Do the necks show any pressure signs; for instance, chamber milling marks engraved into the brass?
By the way, your initial load shot through eight one gallon milk jugs?!?. If you would test again, after you are comfortable with your load, I'd really be interested in seeing just how many jugs it takes to actually stop your bullet.
Sieger