As a basic rule yes, gotta check manufacturer's spec. I have a Mini14 ranch rifle and it eats both calibers no prob. Practice and goof off with Russian Wolf, target shoot with .223. A buddy has an AR and that only eats .223
Saami list shooting 5.56 out of that mini 14 as dangerous. Unless it is 5.56.
Your buddies ar, is it chambered only in .223?
They make them in .223 only. If it is chambered in 5.56 and only likes .223 then may be something wrong with it.
I'm sure there are some .223 that handle 5.56 but I wouldn't do it.
My ar is a mutt. I shopped around and bought blemished upper and lower, got the barrel and other parts from palmetto state armory.
Got less than $350 in it and its probably better than a factory colt.
That's another thing that erks me. There are only a handful of machine shops that make parts for ar-15's. They are all the same thing with different logos.
People think because they have a colt its the best. Hell colt has been known to order Mossberg barrels when they get behind.
As long as the barrel is hammer forges it came from the same place colts barrels did.
This is for anyone to know. If shopping for an ad there are tier 1-3 guns. 1 being the best. Just research which tier the manufacturer is. You can save a lot of money that way.
Plus, if you build the gun you save 11% excise tax.