Replacing 300 Blackout rail?

I bought a completed 16" 300 Blackout upper from a friend. It has a FGS Rail that I'm not a fan of and want to swap it out.

Are 300 Blackout upper receivers the same as AR15 or do they use Ar10 receivers or are they both the same size?


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300 Blk is a shortened, necked up 5.56. It uses an AR 15 upper receiver.

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Originally Posted by gaijin

300 Blk is a shortened, necked up 5.56. It uses an AR 15 upper receiver.

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Thanks, that's what I thought I just didn't want to buy a new rail and barrel nut only to find out it was a larger receiver.

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