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Old 12-01-2011, 09:37   #4
Beard One
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Join Date: Apr 2011
Location: Arlington, VA.
Posts: 15,505
Originally Posted by RustyDaleShackleford View Post
Specifically what parts are different in a piston vs DI build? I can't seem to find parts descriptions.

I've heard that you actually want your castle nut not staked, while you do want your gas key staked. They say it's because the castle nut is unlikely to come loose, is difficult to remove if you decide to, and you can ruin many tools doing it.

I'm not worried about having trouble building the upper from scratch, and would prefer it if it's at all cheaper. I've got a cousin who lives nearby who's built several AR-15's and who said he'll help me and let me use his tools. So the cost of tools isn't a problem.

Is my thinking right? 1:7 is the fastest barrel twist rate, and since it stabilizes the heaviest bullets, that covers me for any bullet weight I'd want to use. Right?
I have never heard of anyone doing a "piston build". Piston ARs are not like DI ARs, where the parts are interchangeable. Piston gas systems are propietary and different from one manufacturer to another.

Do yourself a huge favor, just buy an upper. Building an upper is pretty pointless, considering how cheap they are.
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