is it safe

[big al hunter]

According to SAAMI spec, The .223 Remington is rated for a maximum of 50,000 CUP while the 5.56mm is rated for 60,000 CUP.

I love when these arguments come up. The pressure measurement systems are confusing and it creates this fear unnecessarily. The SAAMI spec for 223 is C.U.P. The military spec is in P.S.I. for 5.56. The P.S.I. spec for 5.56 is 62,366 P.S.I. The P.S.I. spec for 223 rem is 62,366. The C.U.P. equivalent is 52,000. The two systems measure the pressure differently, but to the same pressure when using the same system.

 

[elmbow]

I've shot thousands of rounds of 5.56 through a CZ 527 and never seen a hint of a proble, and it's a mini mauser action. Seriously, if you are the least bit worried shoot 50 rds of 5.56 mil spec ammo through your rifle. If you get bolts that don't want to lift, don't shoot the stuff. I don't think you will.

 

[849ACSO]

Sigh

According to SAAMI spec, The .223 Remington is rated for a maximum of 50,000 CUP while the 5.56mm is rated for 60,000 CUP. DO NOT shoot 5.56 cartridges in a .223 chamber. It might go OK, it might end your life. Why on earth would you chance it when the ammo is the same price? It's completely irresponsible for someone to recommend doing so on a public forum. Go do some study, and then you can come back here and talk with the adults.

I have studied this EXTENSIVELY, hands on. I have shot literally thousands of 5.56 mil spec rounds through a department issued counter sniper rifle, plainly stamped ".223 Remington" on the barrel. I have shot thousands more through my personal rifle, same ammo, same stamp. SAAMI specs on pressure are not "exact", and every one of those rifles are proof tested at 150,000 CUP/PSI and above. Have you ever even heard of one blowing apart, or are you just "being a better adult" than the rest of us who have real life experience?

 

[David R]

My Savage model 25 has difficult bolt lift with 5.56 or a hot 223. One sample. This is a light action, 223 is as big as it could go. I think it's a rear locking bolt.

I was wrong, 3 lug front locking bolt
http://www.gunblast.com/Savage-Model25.htm

It still does not like 5.56. Maybe it's the only one.
David

 

[Gunplummer]

Military brass USED TO BE thicker, I don't know about now. Choking the neck is where some of the pressure comes from. I can't say as anyone ever showed me a .223 damaged by 5.56 ammo, but I have seen .308's with pitted bolt faces where the pressure spit out around the primer. These guys fired a lot of surplus 7.62 through their hunting rifles. You can get the same effect from too many hot loads with .308 brass too.

 

[joe sixgun]

This is very interesting. I have been trying to decide on a range gun that will be economical to shoot and I see alot of the surplus 5.56 in my area. No shortage of .223 either. So I guess either way I will be able to find plenty of ammo. What are some other signs of over pressure to watch for?

 

[849ACSO]

Flattened/flowing primers, the writing on the case heads being "erased", pierced primers, hard to lift bolt handles.........

 

[taylorce1]

I've shot thousands of rounds of 5.56 through a CZ 527 and never seen a hint of a proble, and it's a mini mauser action.

That's because it's a CZ built to European standard chambers, which are not built to American (SAAMI) specifications.

Built to CIP specifications, our .223s will happily eat 5.56, since CIP doesn’t differentiate between the two cartridges and just has the higher pressure as its standard. So our .223s will shoot everything from the cheapest Russian steel to match .223 brass ammo.

 

[Guv]

My newest Speer loading manual doesn't mention any difference between the two. Their biggest comment is about firing light jacketed bullets in too fast of a twist.