Big Guy Posted August 23, 2013 Share Posted August 23, 2013 I usually load my rounds to around 1.235-1.240 (121s w/ 11.5 g of VV 105 out of a Brazos SX). However, I just got some 121s loaded with 9.2 g of IMR 4756 at 1.218. Should I expect any issues for them being so short (e.g., over pressure, not feeding, etc.)? Link to comment Share on other sites More sharing options...
DRichardson Posted August 24, 2013 Share Posted August 24, 2013 I would pull a few of those apart. That is a lot of 4756 and I would think it would be very hard to get that short of a OAL with that much in the case. Link to comment Share on other sites More sharing options...
Guest Posted August 24, 2013 Share Posted August 24, 2013 (edited) I would agree with pulling a few to verify the powder charge, then do a little chrono work to ensure you are making major and of course look for pressure signs along the way. I know these aren't MG 121 grainers but for my guns I found when using a MG 124gr JHP with SR4756 it takes 8.4gr 1.235" oal to get to the minimum of 1335fps/165.5pf. A MG 115gr JHP with SR4756 @ 9.0gr 1.235" oal only got me to about 1410fps/162pf...and i stopped at this point as the case was very full and even with the 115gr bullet's dished in base it was compressed more than I cared for (the 121 is a 115 jhp with a filled in nose cavity). Also, SR4756 is known to vary quite a bit from lot to lot. However, I like SR4756 with the 124 grain bullet - accurate, loads easy, and shoots well. Don't really care for it with the 115gr bullet mainly because loading it is a pain as the case is very full at 9.0gr with my lot of powder and the load is compressed more than I felt comfortable with. As for feeding, that is dependent on your gun so you just gotta try it but I tend to doubt that it would be a problem. Edited August 24, 2013 by Bamboo Link to comment Share on other sites More sharing options...
Shadyscott999 Posted August 24, 2013 Share Posted August 24, 2013 I load 9.3 of 4756 under a MG 121. The case is absolutely full. Sucks to load. I have to be there to make major using a Trubore with 4 poppel holes. I use 4756 for practice and club matches and 3n38 for majors. I am at 1.235 on OAL Link to comment Share on other sites More sharing options...
Big Guy Posted August 24, 2013 Author Share Posted August 24, 2013 Just in case, according to an email from Bob at BCG, he indicates a 124 g with 9.2 g of IMR 4756 @ 1.235 should make 168-170 pf. Link to comment Share on other sites More sharing options...
noylj Posted August 27, 2013 Share Posted August 27, 2013 Umm, not to be too stupid, but are you going to work up to that load or just hope it doesn't blow up your gun? I would have thought that even starting at the .38 Super max of 7.6gn for SR4756 would make more sense (although my .38 super data all shows a COL (AOL is an internet site) of 1.245-1.265", so if I went even lower in COL I would start even lower in charge weight. Then again, even my most excessive N105 load is only 11.0gn at 1.126 for 1475fps, and my major load is 9.9gn at ~1415fps (why go higher for no gain--that spells MAX effective load to me). Link to comment Share on other sites More sharing options...
DRichardson Posted August 27, 2013 Share Posted August 27, 2013 4756 is very temp sensitive and varies from lot to lot. That much, 9.2, of my current lot would be closer to 177-180 in my gun. I'm at 168 PF with only 8.5. YMMV Link to comment Share on other sites More sharing options...
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