Range Report: 300 Blackout SBR

[Netpackrat]

That's brass that just doesn't eject, so the mouths get mashed as it gets shoved back forward... When I get that, it also tries to feed a new round from the magazine. It doesn't happen with the can on.

[Netpackrat]

Fired a couple boxes of SIG 220 grain subsonic today, and they didn't seem to be any different from the others in terms of volume. I think to really get much quieter, it would take a manually operated action, and a quieter/bigger volume can than the SDN-6 would probably help, too.

I started by firing 5 shots unsuppressed at the target to make sure there was no keyholing, etc, which from what I have read is a recommended practice any time you are trying a new sub load, before running it through the can. Probably not necessary with factory 220 grain ammo and a 1 in 7 twist, but it still seems like a good idea. Anyway, I only loaded one in the mag at a time, and noted that although the bolt did lock back, there wasn't enough force to eject the brass, which remained in the action. With the can on, it made a fairly neat little pile of them at about 4 o clock a few feet away.

[Netpackrat]

Today I installed a Geissele G2S trigger group that I bought during the black Friday sale. It breaks right at 4.5 pounds like it is supposed to, which results in a trigger similar in feel to the RSA triggers in my AKs.

I was holding off monkeying with the gas system until after my friend visited from out of state, but numerous factors combined to prevent our trip to the range today. Ended up being a good thing because there was a big pile-up in the area of the range that snarled traffic out there, and would probably have prevented me from making it to the British sports car club's Christmas party. So the next thing is to figure out why it won't run unsuppressed, and hopefully fix that.

[Netpackrat]

Tonight I removed the handguard and the gas block. I found that the gas port was not completely centered in the gas block, as evidenced by the carbon marks on the barrel, but I also don't think the port was obscured, either. It just looked like it was close on one edge, but there was a trace of carbon around that edge too. So I don't think gas block alignment was really a problem. I measured the diameter of the gas port and found it to be .0935" (#42 drill bit), as advertised. Using a #40 drill bit, I opened it up slightly to .098" and reassembled. I ran a bore snake down the barrel to make sure I hadn't left any bits of metal inside, and then oiled down the BCG and charging handle a bit with CLP. The upper was cleaned about 50 rounds ago, so that's as far as I went with that.

Hopefully I'll get to shoot it sometime later today when I am up and about again. The mother in law unit arrived from out of town a few hours ago for a short visit, and it sounds like she'll have the kids for most of the day, so I can go out and play with guns for a while.

[Netpackrat]

Well, it did 3-4 shots of supers unsuppressed before failing to eject and mangling the spent brass, so it still needs work. Since I also needed to test the hanger I made for my 8x10 rifle plate, I stuck the can on and proceeded to lob subs at it. I learned something really quickly... When shooting at the plate, don't bring any more ammo with me than I intend to shoot. The can and the plate are an expensive combination; I could sit there and ring that all day long. The Nikon scope with the BDC reticle made it stupid easy to hit even with subs, since I had previously determined which tick mark to use on paper.

I finally called it a day after a couple of hours and probably 150-200 rounds down range, but not before taking some time to spread the gospel a little. Another guy was there with a friend who was a relatively new shooter, and I let them each shoot the blackout. The one guy had a "Ruger Precision Rifle" in .308 and I was like, "Hey, I see a thread protector on there...." He let me shoot it and I was pleasantly surprised by how it shot. The trigger wasn't bad either. I like to hate on Rugers but it seemed like a pretty good rifle. I expect he'll end up with a can for it at some point.

[JAG2955]

Not to be a douche, but, does it really need to run stuff unsuppressed? I know that you have more than one host, so I suppose that it should, but I have yet to shoot my Blackout SBR without the can on it.

Shooting subs is the best. No ear protection needed at all, but when a 20-rd mag costs $22 bucks to fill with factory ammo, you might need a wallet protector.

ETA: Have you checked the extractor and ejector springs on your bolt?
ETA2: Checked the tightness of the carrier key? Maybe you have enough pressure to reliably move the carrier when suppressed, but not when unsuppressed.

[Netpackrat]

Not to be a douche, but, does it really need to run stuff unsuppressed? I know that you have more than one host, so I suppose that it should, but I have yet to shoot my Blackout SBR without the can on it.

I suppose not, but I want it to have that functionality. I don't care if it won't run subs unsuppressed, but it should at least be able to run supers without the can.

Shooting subs is the best. No ear protection needed at all, but when a 20-rd mag costs $22 bucks to fill with factory ammo, you might need a wallet protector.

Yeah... I went through 3 boxes of SIG subs today, and 2-3 of Remington, plus 3 boxes of UMC supers. Reloading is going to be the way to go; I hope that Rainier comes through with their plated bullets for subs like they are supposedly working on. They were supposed to hit the stores last month. I have 5 pounds of A1680 standing by.

ETA: Have you checked the extractor and ejector springs on your bolt?
ETA2: Checked the tightness of the carrier key? Maybe you have enough pressure to reliably move the carrier when suppressed, but not when unsuppressed.

The springs seem pretty tight, and no motion at the key. The BCG is from Bravo Company, so I doubt it has anything to do with the problem. Maybe I can get to the range with my brother sometime, and switch out parts with his AR to see if that makes any difference. It's probably a good idea to do that anyway before I enlarge the gas port any more.

[JAG2955]

Is the brass getting mangled by the chamber mouth, or by the ejection port sides?

Will it reliably lock the bolt back on an empty mag unsuppressed?

Check the gas rings for funzies, too. If the weight of the carrier will collapse the bolt when placed face down, the gas rings need replacement (supposedly).

And good idea on using your brother's parts. Troubleshoot, then grind on the cheapest part first.

[Netpackrat]

Is the brass getting mangled by the chamber mouth, or by the ejection port sides?

I'm pretty sure it's getting mashed by the chamber mouth/breech face as the rifle tries to shove the empty back in at the same time it's trying to feed a fresh round.

Will it reliably lock the bolt back on an empty mag unsuppressed?

Yes, even with subs. It leaves the empty sitting on top of the mag.

Check the gas rings for funzies, too. If the weight of the carrier will collapse the bolt when placed face down, the gas rings need replacement (supposedly).

Tried that. It won't push the bolt into the carrier. It's pretty dirty right now, but even clean and lubed there is enough resistance there that I don't think it would collapse it. All of the parts were new together, have had the malfunction since the beginning, and the rifle has less than 500 rounds through it.

I do appreciate all the advice on things to check, given that this is my first/only AR. Based on advice elsewhere, I also checked the length of the spring, to make sure I don't have a rifle spring (as opposed to the correct carbine spring).

And good idea on using your brother's parts. Troubleshoot, then grind on the cheapest part first.

At the very least, it will keep me from shooting up more Blackout ammo until we can get together. I really do think though, that it's going to come down to enlarging the gas port little by little until the malfunctions go away. If I later find a "smoking gun" that was really causing the problem after all, I can still install an adjustable gas block to regulate it back down. I do know that AAC uses a much bigger gas port than I have in their uppers, because they want theirs to run both supers and subs, suppressed or unsuppressed.

[Netpackrat]

Also, my homebrewed sling came apart while I was looped up in the kneeling position. So, a new sling is going to be a must.