[P8riot]

Second that. Don’t use 5.56 unless it says “5.56” on the receiver.

[mmanager]

This came off a web-site that was recommended (No?):

Federal 223 NATO Ammunition

Product Number: FAXM193
Product Title: 5.56 NATO 55 GR FMJ BOAT-TAIL
Item Price: $11.69 $8.99
Availability: In Stock

[Dead Corpse]

For lighter barrel profiles, I agree. NATO standard 5.56 is loaded a couple thousand CUPS (pressure measurement) over stock .223. In thinner chambers, it could go nuclear on you.

My 20" 1:9 stainless superbull .223 eats 5.56 with ease. It weighs half a ton compared to my 20" "heavy" profile 5.56 though.

I never did get into the shorter barrels. Something about not letting Tangos get quite that close... I'd prefer to retain the ability to reach out to at least 500yrds. Lugging around a couple extra inches of barrel isn't gonna hurt me any.