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Posted: 2/23/2012 10:49:14 AM EDT
| A friend put a CMMG 9mm upper on an A-2 lower that he had extra. He fired it yesterday and ALL the cases have a bulge ring just above the head of the brass. Not being a 9mm AR guy, I am guessing that the gun is opening before the bullet exits the barrel and the brass is swelling because of the pressure. I am also guessing that he will need a heavier buffer intead of the standard rifle buffer. I have not seen a heavier rifle buffer, so this I think would necessitate changing his stock, buffer tube and spring to a carbine stock setup and getting a 9mm heavy buffer. Am I even close on this guess ???? |
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There are heavier rifle buffers out there. Also hydraulic buffers, both oil & air.
http://www.heavybuffers.com/ar15rifle.html |
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I think you will also need a stock spacer
like these....... http://www.brownells.com/mobile/aspx/search/product.aspx?pid=44889 http://www.brownells.com/mobile/aspx/search/product.aspx?pid=44739 |
I run nothing but A2 stock.. I do not like CAR stocks.
Std A2 buffer weigh similar as the "9MM" CAR Buffer. I have A2 buffer that weighs 7.0oz,,,, dump A2 guts, and replaced with machined brass dowel that slip fit into the body with single rubber pad at bottom, pin the end bumper back in place.. If you really want to go hog wild, I have a stainless A2 length buffer we cut that weighs 12.8oz... I would not suggest this in the AR-15 9mm.. way too sluggish,, this was cut for my TASK style M11-9 SMG for slow fire. 12oz stainless for M11-9 SMG - 
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As noted previously, normally you would use a 9mm CAR buffer with a CAR action spring and a stock spacer in a Colt-style 9mm set up.
Th e9mm operating system was CAR-based and designed to work in the shorter receiver extension. To use it with a rifle extension, you "mechanically fool" it into "thinking" it's in a CAR tube by shortening the internal length (to the internal length of a CAR extension)with the spacer , then use thew CAR spring and 9mm CAR buffer (preferably the two piece mechanical version of it). Steve/RRA |
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