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Old August 23, 2019, 02:42 PM   #68
stagpanther
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Join Date: March 2, 2014
Posts: 11,789
Similar-- a 45 super +P.

I just got back from another session of "working out the bugs" with this build. I was experiencing a fairly high number of cases splitting and getting stuck in the chamber; even with relatively low power loads. I've got a fair amount of experience with blowback AR's in 10mm using Glock magazines--the blown cases are generally not the direct result of an overpowered cartridge; rather the angle of the feed from the Glock magazine often causes the BCG to slam the cartridge with quite a bit of force into the wall of the chamber doing one of two things, sometimes both. 1) it can easily set the bullet back in the case, which can cause a pressure spike; and 2) it stresses the case unnaturally sideways, giving the case a propensity to split at the web.



I had always "blamed" this problem on the high pitch angle of the cartridge as presented by the Glock magazine but I just happened to have a spare new nitrided KAW valley 10mm/40S&W BCG on hand and decided to swap it out with my older BCG, was surprised to see that there was an entirely different construction, the newer one resembles more closely a conventional 9mm carrier--but the "dummy gas key" has been moved significantly forward, as well as using a conventional AR style extractor as compared to the older 10mm BCG. Upon switching to the newer BCG the rifle fired and cycled without a hitch.

The circle 10 lower came assembled, but apparently came with a conventional strength bolt catch--in a blowback 10mm this will eventually fail, and mine blew apart today on about the 10th round down the tube. I replaced it with a seekins enhanced bolt catch--I would prefer to use a titanium one but those are basically "unobtainium."

PS-- I've actually found a few--but they are generally around $100 a pop!
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Last edited by stagpanther; August 24, 2019 at 04:25 PM.
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