Please set me straight.  I have an American Spirit AR, 1:8 twist, stainless bull Walther-Lother (Spelling?) barrel.  I understand that I should be shooting .223.  Is there any problem if I use 5.56?  I'm not sure of the differences, if indeed there are any.  I also understand that the 1:8 twist handles a heavier bullet better. The 55gr .223 I've been shooting cannot group worth a darn (S&B).  Please offer your guidance, and THANK YOU.

If the barrel is stamped and rated for .223 Rem ammo, DO NOT shoot 5.56 in it.  5.56 is generally loaded hotter as well as having a slightly longer neck.  Shooting 5.56 in a .223 Rem chambered gun causes high pressures, and can Ka-boom.  Refer to the ammo-oracle sticky at the top of the ammo forum.  Read it, memorize it.  Its good info.  

Ghost

It should be marked, if it's marked 223 I would stick with what Ghost-Shooter said, 5.56 is a [b]much[/b] higher pressure cartridge than 223.

The 55gr S&B is mfgr-rated fairly hot (3,300 fps). While I get good accuracy from my DPMS 1x9 HBAR with S&B, especially out to 200 meters, maybe your 1x8 is a bit too fast a twist for the S&B to stabilize.

Suggest you try some 62gr just for comparison. Both Federal Am Eagle and Winchester USA brands have .223 in 62gr (I believe S&B also makes 62gr, but it may be more difficult to get). In addition to using the heavier bullet, they are both rated slower than the S&B 55gr.

Both bullet-weight and bullet-speed factors may be at work here in your case.

Don't try the Olympic SS109 ... while 62gr, it is 5.56 and not advisable for use in your .223-chambered barrel, as already noted.

Ghost-Shooter, Wingman, and JoeinCt, THANK YOU.  The bbl is indeed marked .223.  I read the ammo-oracle last night, and I realized that the 5.56 was not for me.  You all certainly reaffirmed that.  I'll search out some 62gr fodder and see what that does.  Thank you all again, and Merry Christmas.

[i]Bull Twinkies.[/i] [;)]

This rifle can shoot 5.56mm Ball all day long without any safety issues.

Your rifle may be too tightly chambered for reliable autoloading, but that's the only issue.

The most common ".223" ammunition sold in bulk is stuff like the South African surplus military ",223" which started life as 5.56mm.  Was converted to ".223" by the highly technical operation of pasting ".223" labels over the 5.56mm on the box.  If there were going to be "kabooms" the liability issues for converting this ammunition would be insurmountable.

If there are [i]documented[/i] "kabooms" directly linked to shooting 5.56mm ammunition from any ".223" AR15/M16 I'd appreciate a link.  If this was dangerous there should be thousands of 'em.

-- Chuck

Ha ha.   I couldn't have said it better myself.


Oh, and the 55gr will be just fine in a 1:8" barrel.  You'll be better served (accuracy-wise) with some 68 or 69gr BTHP.

[rolleyes]

Thank you all for your timely and responsive posts.  I picked up some 62 gr today and will shoot it tomorrow.  I have a source for some 69 gr that I want to try as well.  Thank you all again.

Since no one else has said it, the reason you're getting bad groups is probably because you're shooting crap ammo. S&B is fine plinking ammo, but you've got a fine barrel on there and you're feeding it junk food.  Get on over to [url=www.georgiaprecision.com]Georgia Precision[/url] and get some 68, 69, 75, or 77gr Black Hills Blue Box.  That barrel ought to be capable of sub-MOA all day, if you do your part.