SIG SB15 brace build thread

[GJM]

So tonight, my wife and I go out to zero her AAC .300 BLK AR pistol, using Barnes factory Vortx ammo. After shot six, the bolt is locked up, out if battery. I had to take a 2x4 off a target stand to beat it open. From that point on, bolt carrier and bolt won't seat forward. Back at the cabin 100 miles from town, I disassemble and compare with a Colt 6920 upper. Both bolt carrier assemblies work fine in Colt upper. Neither works in .300 upper. YVK thinks something got loose or out of spec with the barrel extension -- this make sense? Any trouble shooting ideas, other than to send it back to AAC?

[Suvorov]

So tonight, my wife and I go out to zero her AAC .300 BLK AR pistol, using Barnes factory Vortx ammo. After shot six, the bolt is locked up, out if battery. I had to take a 2x4 off a target stand to beat it open. From that point on, bolt carrier and bolt won't seat forward. Back at the cabin 100 miles from town, I disassemble and compare with a Colt 6920 upper. Both bolt carrier assemblies work fine in Colt upper. Neither works in .300 upper. YVK thinks something got loose or out of spec with the barrel extension -- this make sense? Any trouble shooting ideas, other than to send it back to AAC?

We had a customer show up at the range about a month ago with two brand new AAC uppers. After a few shots they locked up like you mentioned, the BCG would fail to go into battery after locking up. Swapped out the BCGs with another AR and the BCGs seemed fine (the rifle was 556 so it didn't fire obviously). Near as I could tell, it seemed the hang up was on the gas tube - as the tube heated up it expanded and caused the mischief. I advised him to send them back to AAC as maybe they had a batch of out of spec gas tubes? I haven't see the guy since, so I never did get any follow up.

If you have the tools (which I imagine you do), maybe try a new gas tube?

[YVK]

That upper has the URX 3 rail. Unless 3 is different from 2 and 1, it requires some special tools to remove.

G, when you get back home, take some hi-res, magnified pics of bbl extension and gas tube. In a pic you sent me the tube seems slightly different than mine, as if the tip is broken on yours, but angle is different too.

[GJM]

The gas tube idea is a good one. When I stripped the BCG, it won't go all the way forward -- same as when fully assembled. To my ameteur eyes, the gas tube looks off center:

[GJM]

Pretty funny afternoon. Since my wife's .300 BLK was TU, she confirmed zero on her .450 Marlin, built on a model 70. It starts a 400 grain a Swift bullet at 2,150 fps -- essentially a .458 lite in a 6.5 pound rifle. After shooting six rounds, my wife pronounced the AAC .300 BLK was a LOT more fun to shoot!

[Suvorov]

The gas tube idea is a good one. When I stripped the BCG, it won't go all the way forward -- same as when fully assembled. To my ameteur eyes, the gas tube looks off center:

Interesting to know. Like I said yours would be the third AAC upper with this issue that I know of. Wonder if they have started sourcing Bushmaster parts?

[LHS]

Well, it was only a matter of time. CNC Warrior is selling a side-folding AK brace adapter for the Yugo PAP pistols.

http://www.cncwarrior.com/ProductDet...ductCode=26561

Now you can choose to use your brace or fold it out of the way, for compactness.

It's getting harder and harder to resist something like this for my Draco.

[helothar]

Palmetto State Armory is having a 4th of July sale. Stripped lowers are $49.99 with free shipping. That's better than the Aero deal. With that said, I ordered my Aero blems before I found out about the PSA deal. Would have went that way just to save some extra $. The Aero blems seem to be high quality and the fit to my DD upper is excellent.

Thanks! I got my order in for one of the PSA lowers

[Mitch]

Any more range reports on these? I'm very tempted to build my own that would fit in a saddle bag on a motorcycle.

[JM Campbell]

http://www.law-guns.com/ar-15300blac...tolbarrel.aspx

I'll be your Huckleberry.

8" 300blk pistol build here I come.

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