Firearms Stack Exchange Archive

If my Bushmaster XM15-E2S is marked with “CAL. 223 5.56mm” is it safe to fire 5.56x45 NATO rounds with it?

• posted by: dgm on 2011-11-01
• tagged: gun-safety, ar-15, ammunition, 5.56x45, bushmaster
• score: 3

In the comments of another question, it was stated that Bushmaster rifles are not truly chambered in 5.56x45 NATO, but only marketed that way.

The receiver of this particular rifle is stamped as stated in the title, and the manual also specifies that the XM15-E2S is chambered for 5.56x45 NATO.

Can I use 5.56x45 NATO rounds in this rifle safely and without damaging the rifle?

Answer 115

• posted by: GEOCHET on 2011-11-01
• score: 3

The Bushmaster XM15-E2S is chambered for 5.56x45. It is safe to fire both .223 and 5.56x45 ammunition in it.

http://www.ar15.com/content/manuals/manual_bushmaster.pdf

Answer 121

• posted by: Alan on 2011-11-01
• score: 2

Yes it is safe to fire both the .223 and 5.56x45 out of that rifle. If the rifle was only marked .223 I would not fire 5.56x45 out of it, it would fit and fire but the 5.56 round is a higher pressure round and could damage the gun or the shooter.

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