It might not be a bad idea to have a problems ongoing or solved thread. I kind of look for one 
If this sounds like your problem there is a solution. I've been chasing a problem with my Dead Air Sandman-L and my .300 Blackouts. One is an AR platform and one is the Ruger American. I use the Dead Air muzzle brake style Key-mo. I finally solved the first problem and I think I know what the 2nd problem is.
(1) I could sight either rifle in at 50 yards, with subs btw, without the can and and it would drive tack. Big tacks 1 moa or a little less at 50 yards is a reasonable estimate of group size. I checked the drop at 100 and with subs, it's significant. But I knew what holdover should be. Then I shot supers and did the same thing except I didn't change zero. Life is good, time to put the Sandman-L to work. I set up at 100 yards since I knew what to hold over (third line down on the FFP 8x scope reticle). Shot 3 rounds. Walked down. The target was clean. No holes. Moved to 50. Shot 3 rounds. No holes. Walked to the target. Still now holes. So I switched to the rifle and basically did the same thing and got the same results. Conclusion - something is wrong with the Sandman-L, the Key-mo, etc.
But I did one more test. I had a roll of 4' wide piper so I covered the entire backdrop (4x8) with white paper. This was the 25 yard backdrop btw. I put a dot around the center and shot. Nothing. NOTHING. I was stunned. There was one other guy at the range and I walked down to talk to him about it. He says "I've been sighting in my rifle today and I can show you how to sight yours in if you would like". He'd been there a good 3 hours but you know... sometimes it pays to accept help and he didn't mean anything rude by what he said. It's pretty funny now.
I showed him what I was doing lol. The front of the rifle sits in an expensive rest with an elevation adjustment. The rear bag is a very heavy leather bag. Once the crosshairs are on target they don't move. I sent a round downrange. He immediately said you hit about 3' in front of the backdrop. I said, hit what, he said, the ground. WT? I asked him to shoot and let me watch. Sure as he double toothpicks, there was a puff of dust at the time he shot. It was about 3' in front and a little left. He, btw, did manage to get on paper because the bullet skipped up and into the backdrop. I took the can off checked the rifle and AR and there were no issues. Can problems... well... yes and no. I dug into that when I got home AND after I ordered some "stuff" to check it with.
I bought a Geissele alignment rod. Perfect alignment. I inspected the baffles, no strikes. I check the end cap. No strikes. I measured the hole in the end cap. .3085. <-- hold that number in memory. I contacted Dead Air. Sort of, I found out, through connections, that they are moving to a bigger facility and right now, they aren't helping much. The best I got was send it in and we'll inspect it. Except they are moving and not taking calls or answering emails. So it's not going anywhere until they resume normal operations. 6 months into this thing I was at a loss for what to do. I mic'd the bullet od. I mic'd the end cap (remember the diameter from before). I checked my end caps. .308 was missing, 6.8 SPC was there, .223 was there. No way it was the wrong end cap. I called my son told him what I was doing. A day or so later he brought me a .308 endcap and said this is yours. I said no, mine is on my Sandman-L. He said no... I swapped to .223 the last time I borrowed it (yes he is on my trust). Sure enough... But you know what, the .223 cap didn't have bullet strikes and it mic's .3085. Nothing had strikes. I swapped the caps out and the supers work great in both rifles. The subs... it depends. With the can on the Gorilla ammo, arguably not the best ammo out there, keyholes (like the hole is the shape of the bullet), with the AR, sometimes. Sometimes it does ok. Sometimes it shoots high right. Sometimes it shoots low left. My sub reloads don't keyhole but they aren't consistent either. They don't eject reliably in the AR. They work ok in the bolt gun but I couldn't hunt with them. If I take the can off the subs work fine. The supers work no matter what.
The answer to the first problem is to use the right end cap. I never had a strike but the end cap definitely disturbed the bullet path. Especially with a bullet that's already not that stable. The .308 end cap doesn't look like the .223 end cap. Aside from the larger hole size there are three dimples in the edge of the hole. I won't make that mistake again.
The 2nd, new, problem, I believe, is an issue with bullet instability at subsonic velocities. The supers shoot great (different bullet though). I don't think the twist is fast enough for the heavy bullets moving at relatively low velocity. For my reloaded subs I'm going to run some powder tests and try to find a velocity that will work. I think the Gorilla ammo is so inconsistent, coupled with the dynamics of how cans work, that the odds of the Gorilla subs keyholing are increased. They must be tumbling downrange. The hole they leave literally looks like a long boattail bullet.
I have a 1:5 twist barrel coming for the Ruger American. If I stick with the .300 BLK in the AR and the new barrel for the Ruger settles the subs down I may rebarrel the AR in 1:5 or 1:6 twist. Again, 6 months of chasing problems with the .300 BLK and that problem should have never happened. I really thought I was done with it until I shot today.
If this sounds like your problem there is a solution. I've been chasing a problem with my Dead Air Sandman-L and my .300 Blackouts. One is an AR platform and one is the Ruger American. I use the Dead Air muzzle brake style Key-mo. I finally solved the first problem and I think I know what the 2nd problem is.
(1) I could sight either rifle in at 50 yards, with subs btw, without the can and and it would drive tack. Big tacks
1 moa or a little less at 50 yards is a reasonable estimate of group size. I checked the drop at 100 and with subs, it's significant. But I knew what holdover should be. Then I shot supers and did the same thing except I didn't change zero. Life is good, time to put the Sandman-L to work. I set up at 100 yards since I knew what to hold over (third line down on the FFP 8x scope reticle). Shot 3 rounds. Walked down. The target was clean. No holes. Moved to 50. Shot 3 rounds. No holes. Walked to the target. Still now holes. So I switched to the rifle and basically did the same thing and got the same results. Conclusion - something is wrong with the Sandman-L, the Key-mo, etc.But I did one more test. I had a roll of 4' wide piper so I covered the entire backdrop (4x8) with white paper. This was the 25 yard backdrop btw. I put a dot around the center and shot. Nothing. NOTHING. I was stunned. There was one other guy at the range and I walked down to talk to him about it. He says "I've been sighting in my rifle today and I can show you how to sight yours in if you would like". He'd been there a good 3 hours but you know... sometimes it pays to accept help and he didn't mean anything rude by what he said. It's pretty funny now.
I showed him what I was doing lol. The front of the rifle sits in an expensive rest with an elevation adjustment. The rear bag is a very heavy leather bag. Once the crosshairs are on target they don't move. I sent a round downrange. He immediately said you hit about 3' in front of the backdrop. I said, hit what, he said, the ground. WT? I asked him to shoot and let me watch. Sure as he double toothpicks, there was a puff of dust at the time he shot. It was about 3' in front and a little left. He, btw, did manage to get on paper because the bullet skipped up and into the backdrop. I took the can off checked the rifle and AR and there were no issues. Can problems... well... yes and no. I dug into that when I got home AND after I ordered some "stuff" to check it with.
I bought a Geissele alignment rod. Perfect alignment. I inspected the baffles, no strikes. I check the end cap. No strikes. I measured the hole in the end cap. .3085. <-- hold that number in memory. I contacted Dead Air. Sort of, I found out, through connections, that they are moving to a bigger facility and right now, they aren't helping much. The best I got was send it in and we'll inspect it. Except they are moving and not taking calls or answering emails. So it's not going anywhere until they resume normal operations. 6 months into this thing I was at a loss for what to do. I mic'd the bullet od. I mic'd the end cap (remember the diameter from before). I checked my end caps. .308 was missing, 6.8 SPC was there, .223 was there. No way it was the wrong end cap. I called my son told him what I was doing. A day or so later he brought me a .308 endcap and said this is yours. I said no, mine is on my Sandman-L. He said no... I swapped to .223 the last time I borrowed it (yes he is on my trust). Sure enough... But you know what, the .223 cap didn't have bullet strikes and it mic's .3085. Nothing had strikes. I swapped the caps out and the supers work great in both rifles. The subs... it depends. With the can on the Gorilla ammo, arguably not the best ammo out there, keyholes (like the hole is the shape of the bullet), with the AR, sometimes. Sometimes it does ok. Sometimes it shoots high right. Sometimes it shoots low left. My sub reloads don't keyhole but they aren't consistent either. They don't eject reliably in the AR. They work ok in the bolt gun but I couldn't hunt with them. If I take the can off the subs work fine. The supers work no matter what.
The answer to the first problem is to use the right end cap. I never had a strike but the end cap definitely disturbed the bullet path. Especially with a bullet that's already not that stable. The .308 end cap doesn't look like the .223 end cap. Aside from the larger hole size there are three dimples in the edge of the hole. I won't make that mistake again.
The 2nd, new, problem, I believe, is an issue with bullet instability at subsonic velocities. The supers shoot great (different bullet though). I don't think the twist is fast enough for the heavy bullets moving at relatively low velocity. For my reloaded subs I'm going to run some powder tests and try to find a velocity that will work. I think the Gorilla ammo is so inconsistent, coupled with the dynamics of how cans work, that the odds of the Gorilla subs keyholing are increased. They must be tumbling downrange. The hole they leave literally looks like a long boattail bullet.
I have a 1:5 twist barrel coming for the Ruger American. If I stick with the .300 BLK in the AR and the new barrel for the Ruger settles the subs down I may rebarrel the AR in 1:5 or 1:6 twist. Again, 6 months of chasing problems with the .300 BLK and that problem should have never happened. I really thought I was done with it until I shot today.
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