5.56 NATO vs .223 Remington

[Gunmaster45]

Won't any AR-15 with a steel reciever (not alloy crap they usually make them with) withstand higher pressure? My Bushmaster has a steel reciever, so I'm wondering.

[Yournamehere]

Actually the original models were all manufactured with high strength Aluminum recievers, and they took the 5.56mm NATO rounds, but as we've learned before, the reciever can be made of pretty much anything, (like plastic or wood). The upper should be fully constructed of steel, and almost always is. A steel reciever would probably make the gun a bit tougher, but add some weight as well.

[Gunmaster45]

Yeah, my Bushmaster is a carbine and is just as heavy as a full length Colt HBAR, because the Bushmaster is better made of more solid metal.

[Nyles]

Actually, the difference is in the leade (the space between the end of the cartridge and where the rifling starts. It's somewhat longer in the 5.56mm NATO, which can lead to reduced accuracy when firing some .223 cartridges out of a NATO chamber, or reliability when firing NATO ammo out of a match-grade .223 chamber.

NATO allows a different max pressure than SAAMI, but that's got more to do with different methods of measuring than anything - the European proof houses give the same max pressure for both. Military cartridges have thicker brass since they're more concerned with reliability than reloadability. SS109 or Mk.262 could potentially lead to higher pressure in a .223-spec chamber, but not so much that it's gonna blow up in your face.

[Phoenixent]

Thanks Nyles for explaining the difference between .223 Rem and 5.56 NATO.

We had a PD bring in their Bushmaster built carbines with stainless steel barrels as they would not function on Full Auto firing 5.56 NATO. We had to go in with a 5.56 NATO chamber reamer and give them the correct chamber for the cartridge. Once that was done they worked perfect in Full Auto mode.

[Phoenixent]

Originally Posted by Yournamehere

The upper should be fully constructed of steel, and almost always is. A steel reciever would probably make the gun a bit tougher, but add some weight as well.

Link please to a government used steel receiver on a M16 or AR-15 civilian model.

If no link company name would do.

[Yournamehere]

Eh, GM just said his Bushmaster is built on a steel receiver. It doesn't really matter what it's made of, though, as I've said.

[Gunmaster45]

Maybe I'm wrong, but the thing feels too damn heavy to be aluminum to me.

[Yournamehere]

Actually on the Bushmaster Website, it says that their receivers are either aluminum or carbon fiber, no steel, so you probably have an aluminum one, and yes, they are a bit heavy even with this. Aluminum isn't a helluva lot lighter than steel, depending on what's being forged.

[Gunmaster45]

Huh, I learned something.