BigNate Posted March 16 Author Report Share Posted March 16 250gr subs 250gr SMK (2nds from Midway) 15.8, 16.6, 15.4, 15.2, 15.0, and 14.8 gr of Accurate 1680 through a friend’s Hybrid 46. Totally hearing safe… and functions well (this is with the standard carbine spring and buffer). Without the suppressor, the gun ran well from 16.6gr > 15.0gr - but started to fail to fully eject at 14.8gr. Reformed Hornady 6.5cm brass, CCI #200 primers, 2.750 COAL… Quote Link to comment Share on other sites More sharing options...
shooterrex Posted March 16 Report Share Posted March 16 Cool Quote Link to comment Share on other sites More sharing options...
BigNate Posted March 27 Author Report Share Posted March 27 OK - some load data and an interesting finding... I picked up a bunch of 300gr Nosler CC HPBT blems and built a bunch more sub rounds. I saw some shared load data for these bullets that looked very much like the load that I had worked up for the 250s so I made a few with the 300s (figured they were subs and WAY below peak pressure so I was not worried about pressure spike - and the shared load info that I had seen used .2gr less of the same powder). So - anyway - both sets were: Accurate 1680 - 15.6gr CCI #200 primer 1.685" case length (re-formed Hornady 6.5cm brass) 2.750 COAL (the 300s were .6633 in the case - the 250s were .5216 in the case) No crimp - there is plenty of neck tension - when I tear these down with the kinetic hammer thing it takes a few really good whacks to unseat the bullet... I'll probably soft crimp the next set. It was a family shoot day and there were some new shooters who needed attention - so I only chrono'd a few of each. Interestingly the heavy bullets, on the same charge, gave essentially the same velocity (the range was 973 - 1004 FPS). I'll get better data next time out when there are not as many folks to manage. The other big discovery is that these functioned nicely with the H3 buffer and Sprinco red spring. If memory serves the Gorilla 285gr subsonic rounds clocked on Tom's Magneto Speed at like 860FPS. I'm thinking that those loads are VERY light / soft. I'm guessing that I got the same velocity out of the same charge under the heavier bullets because the deeper seat, greater release friction, and heavier bullet gave the powder a bit more time to build pressure and gave a bit more complete burn (guessing... if anyone knows of a place where folks nerd out on internal ballistics math, chemistry, and physics - let me know - trying to dive in a bit on that stuff). I suspect that a bit of crimp will contribute to that as well. Hopefully next time I'll be able to get better chrono data and collect group data as well. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted March 28 Report Share Posted March 28 AWESOME info, Nate!!! I think you're correct with what's going on speed-wise, with the different projo weights. Your Accurate 1680 load is pretty much the same charge weight (and powder) that I use for my 150gr .300BLK loads... Quote Link to comment Share on other sites More sharing options...
BigNate Posted April 1 Author Report Share Posted April 1 (edited) OK - new chrono data (and a new chrono - picked up a Garmin Xero - I'm like a kid in the candy store with that thing...)... The ladder for the 300gr HPBT blems Cartridge 8.6 Blackout Bullet Nosler338 300gr HPBT Custom Comp Powder Accurate 1680 Case Hornady 6.5 CM Reshaped to 8.6 Case Len 1.682" COAL 2.750" Reloader Dillon RL550B Dies Lee Pacesetter FLSD, Seating, Crimp - Dillon Powder Notes Resized, then hand primed, then loaded on the progressive starting with powder fill Grains Average SD ES Count 16.0 967.1 19.9 62.3 10 15.7 961.7 10.0 31.9 8 15.4 948.2 12.1 38.2 10 15.1 940.0 18.3 63.6 10 14.9 918.8 16.5 57.0 10 The two missing rounds at 15.7gr of powder were failure to fire... of the 50 total in the ladder these were the only two malfunctions and I'm pretty sure that they were my fault - the primers were seated too shallow on these - had a good dimple but no bang... Other than those two - the gun functioned nicely. And the data for a few of the 250gr HPBT blems Cartridge 8.6 Blackout Bullet Midway Blem 250gr HPBT (understood to be SMK 2nds) Powder Accurate 1680 Case Hornady 6.5 CM Reshaped to 8.6 Case Len 1.682" COAL 2.750" Reloader Dillon RL550B Dies Lee Pacesetter FLSD, Seating, Crimp - Dillon Powder Notes Resized, then hand primed, then loaded on the progressive starting with powder fill Grains Average SD ES Count 15.6 1007.8 18.2 74.0 23 The 250s were being shot against the H3 buffer and sprinco red spring. In the 24 shots (I removed one outlier from the group - 823 fps) I had 4 malfunctions - failures to fully eject - that chewed up the brass - so I decided to stop shooting it... I'll try again when the silencer comes in - or will throw the standard carbine spring and buffer in the thing to burn up the rest of those rounds. On the 250s, I may try to reset the seating die and push the bullet deeper into the case - to see if this helps build a bit more pressure... Edited April 1 by BigNate Quote Link to comment Share on other sites More sharing options...
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