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View Full Version : Need Some Ammo Clarification Please


orb451
10-16-2009, 8:33 AM
Hey all, Happy Friday! My first question is regarding ammo. I have a 5.56 upper with 1/7 twist. I did my search on twist rates and bullet weights and I think I get that part. That 1/7 twist *should* generally shoot anything from 55gr up to 75gr or thereabouts and is generally happier with heavier bullets. Is that the general rule of thumb and is the above correct?

My other question is regarding ammo caliber. Is .223 the same as 5.56? It's close right? But not the same, that's my understanding, different brass wall thicknesses, 5.56 is set to SAAMI specs, etc. But just to clarify, if ammo is labeled .223 I'm getting the ammo that's shorter, doesn't sit in the throat of the barrel all the way and has lower chamber pressures correct?

For a heavier bullet, say 70gr and up, what exact label should I be looking for? MK262? Any lines on cheap, brass cased, heavy bullet (70-77gr) or is that just wishful thinking on the cheap part?

Thanks for the help!

R............

DDRH
10-16-2009, 8:41 AM
http://ammo.ar15.com/ammo/


5.56 is diff from .223.

5.56 chamber can handle .223, but not the opposite.

Yes, 1/7 should be able to shoot 55-79gr, maybe heavier too.

i think black hills produce some Mk262

coop44
10-16-2009, 8:54 AM
Hey all, Happy Friday! My first question is regarding ammo. I have a 5.56 upper with 1/7 twist. I did my search on twist rates and bullet weights and I think I get that part. That 1/7 twist *should* generally shoot anything from 55gr up to 75gr or thereabouts and is generally happier with heavier bullets. Is that the general rule of thumb and is the above correct?

My other question is regarding ammo caliber. Is .223 the same as 5.56? It's close right? But not the same, that's my understanding, different brass wall thicknesses, 5.56 is set to SAAMI specs, etc. But just to clarify, if ammo is labeled .223 I'm getting the ammo that's shorter, doesn't sit in the throat of the barrel all the way and has lower chamber pressures correct?

For a heavier bullet, say 70gr and up, what exact label should I be looking for? MK262? Any lines on cheap, brass cased, heavy bullet (70-77gr) or is that just wishful thinking on the cheap part?

Thanks for the help!

R............

Shilen barrels has a good chart covering twist rates and bullet weight, check it out.

223 should run just fine in a 556 chamber. the problems arise when shooting 556 in a 223 chamber, doing a cast of your chamber should clear things up

cheap heavy bullet ammo is indeed wishful thinking.