![]() ![]() The GMX bullet needs the shorter OAL due to it's canalure placement.ĥ5grHornadyFMJ OAL=2.250 barrel=10.5 Brass=28.5grWater HERCO=(11.3gr 74.8%) 2250fps max pressure 52354psi, at muzzle 9368psi 100.0% powder burned So, using QuickLoad - I figured out a load which should perform well.ĥ5grHornadyGMX OAL=2.200 barrel=10.5 Brass=28.5grWater HERCO=(10.9gr 76.1% filled) 2247fps max pressure 52864psi, at muzzle 8944psi 100.0% powder burned. Shorter barrels supposedly have a huge amount of muzzle flash, muzzle noise, and vibrations in the air - due to high muzzle pressure and so much un-burned powder. In 2020 I purchased a 10.5 inch upper for it. Was told by the dealer I can make it pistol or a rifle - I made it a pistol. In 2016 I purchased a stripped AR lower - I called it "Hillary Insurance". Now I am vaccinated, but the gun club does not pro-rate buying a range badge for half of a year, so I am waiting until the end of this year 2021 to pay. They raised the price to $200 per year, and I only go to shoot once or twice a year. Well, I will tell you about an experiment I am doing with 5.56 NATO which - if successful, may be helpful with 300 blk subsonic.ĭecember of 2019 I did not renew the range badge at my gun club. I want to get as much as I can out of my 300BLK handgun, I assume you do too, but I've always thought of this bullet weight/load to be a. Hopefully I'll remember this post and put it here. If I get to it first I'll post somewhere. Don't do this with work hardened brass.įWIW, I expect to need to do this with my 10.3" barrel also eventually (hopefully soon, my too busy definition of soon), so any data you get I'd appreciate having it posted here. When the brass starts to flow at the case head you're near or above max' pressure. ![]() If you see any change in dimension on those 2 points you measured you don't want to go any further and it's strongly suggested to back it down. Fire it and allow it to come down to near the temp you measured it at. ![]() You'll actually be measuring the case in front of the rim. Take a piece of brass and mark 2 points 180°across the case head (mark on the headstamp). RB288, You can determine maximum pressure for yourself if you have a mic' that can read to the. I understand the barrel length differences, and extrapolating the velocities in would fall in at about 25 to 30 fps per inch which is about right.Īccuracy was good for the sbr at 25 yards a solid 1 inch group.Īnyway, just wondering about pushing to boundaries for the sbr a bit.īTW, there were no signs of any excessive pressure on any of the brass.Īlso, they were shot through a SpecWar 7.62 suppressor.Īny thoughts would be greatly appreciated. Now all these loads are at the max end of the "recommended" levels.Ĭan I push those upper limits to try to get the sbr to about 1050, or am I tempting fate too much? The main issue is that the same loads out of my 8.25" sbr average around 850 for the CFEBLK and about 920 for the H110. ![]() These are all, substantially above what the manuals list. Out of my 16" ar, I was getting from 1125 to 1175 as my averages for the CFEBLK loads and around 110 to 1150 on the H110 loads. I was loading some 220 gr subsonic loads for my 330blk. ![]()
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