AR15 ammo, OK to switch?

Bellasogno · May 19, 2012, 08:23 AM

Apologies if this has already been posted -

I have a Smith & Wesson M&P Sport AR (5.56) and since it's purchase have only fired Federal 223 REM. 55 grain FMJ rounds through it. It's time to restock the ammo cabinet, and Federal 5.56 was on sale, however, I recall a gentleman selling ammo at a gun show advising me to pick one or the other & stick with it. 223 or 5.56 that is.

Why? I could see how the accuracy of my rounds could be affected, but I could simply re-sight the scope if needed. What other ramifications present themselves if I were to use both 223 & 5.56 rounds?

Sorry if this is a stupid question. I'm a bit new to the overall experience, and have a lot to learn.

Technosavant · May 19, 2012, 09:08 AM

You'll be fine... with a 5.56 chamber you can shoot either one with no problems. He might have been thinking about carbon buildup in a 5.56 chamber from .223 ammo, but that's really not a concern- if you're worried, just look in there and give it a good scrub.

So long as you stick with the same bullet weight, you shouldn't need to re-zero your sights/optic.

Art Eatman · May 19, 2012, 09:14 AM

Rifles set up for the 5.56 GI round have a tad more room between the case mouth and the rifling, known as the leade. Those set up for .223 have less of this free bore and a 5.56 round could possibly create a bit higher pressure when fired.

No problem firing .223 in a 5.56 chamber. (And, the reality is that few problems have ever been credibly reported from firing 5.56 in .223 chambers.)

Your rifle, set up for 5.56, will be quite happy with either.

RC20 · May 19, 2012, 11:52 AM

You may have a bit of point of impact shift.

No issue with shooting anything in 223 or 5.56 in the gun mechanically. If its chamber for 5.56, then it will take any 223 with no issue

Rounds you can average it, select one over the other or not worry about it

For shooting groups you can just accept it hits a bit off and measure the groups as they are.

If you want spot on then shift to whichever one is your choice.

If you are using it for SD, its going to be so close out to 50 yards at least as to make no difference.

Yote and such as t150 yards then you have to decide which one is the yote cartridge.

Bellasogno · May 19, 2012, 04:42 PM

Thanks everyone. Off to go buy a ammo can of 5.56.

This AR stuff is a real hoot. I love this gun. Next step - Armalite 308 AR

eldorendo · May 19, 2012, 05:30 PM

If you find a great deal on bulk .223, don't hesitate to try it. You won't be able to tell the difference.

May 19, 2012, 08:23 AM	#1
Bellasogno Member Join Date: August 14, 2011 Location: Rural, outside of Milwaukee, WI. Posts: 76	AR15 ammo, OK to switch? Apologies if this has already been posted - I have a Smith & Wesson M&P Sport AR (5.56) and since it's purchase have only fired Federal 223 REM. 55 grain FMJ rounds through it. It's time to restock the ammo cabinet, and Federal 5.56 was on sale, however, I recall a gentleman selling ammo at a gun show advising me to pick one or the other & stick with it. 223 or 5.56 that is. Why? I could see how the accuracy of my rounds could be affected, but I could simply re-sight the scope if needed. What other ramifications present themselves if I were to use both 223 & 5.56 rounds? Sorry if this is a stupid question. I'm a bit new to the overall experience, and have a lot to learn. __________________ Blaming guns for crimes is the same as blaming forks for obesity.

May 19, 2012, 04:42 PM	#5
Bellasogno Member Join Date: August 14, 2011 Location: Rural, outside of Milwaukee, WI. Posts: 76	Thanks everyone. Off to go buy a ammo can of 5.56. This AR stuff is a real hoot. I love this gun. Next step - Armalite 308 AR __________________ Blaming guns for crimes is the same as blaming forks for obesity.

May 19, 2012, 09:08 AM	#2
Technosavant Senior Member Join Date: May 29, 2007 Location: St. Louis, MO area Posts: 4,040	You'll be fine... with a 5.56 chamber you can shoot either one with no problems. He might have been thinking about carbon buildup in a 5.56 chamber from .223 ammo, but that's really not a concern- if you're worried, just look in there and give it a good scrub. So long as you stick with the same bullet weight, you shouldn't need to re-zero your sights/optic.

May 19, 2012, 09:14 AM	#3
Art Eatman Staff in Memoriam Join Date: November 13, 1998 Location: Terlingua, TX; Thomasville, GA Posts: 24,798	Rifles set up for the 5.56 GI round have a tad more room between the case mouth and the rifling, known as the leade. Those set up for .223 have less of this free bore and a 5.56 round could possibly create a bit higher pressure when fired. No problem firing .223 in a 5.56 chamber. (And, the reality is that few problems have ever been credibly reported from firing 5.56 in .223 chambers.) Your rifle, set up for 5.56, will be quite happy with either.

May 19, 2012, 11:52 AM	#4
RC20 Senior Member Join Date: April 10, 2008 Location: Alaska Posts: 7,014	You may have a bit of point of impact shift. No issue with shooting anything in 223 or 5.56 in the gun mechanically. If its chamber for 5.56, then it will take any 223 with no issue Rounds you can average it, select one over the other or not worry about it For shooting groups you can just accept it hits a bit off and measure the groups as they are. If you want spot on then shift to whichever one is your choice. If you are using it for SD, its going to be so close out to 50 yards at least as to make no difference. Yote and such as t150 yards then you have to decide which one is the yote cartridge.

May 19, 2012, 05:30 PM	#6
eldorendo Senior Member Join Date: May 8, 2012 Posts: 239	If you find a great deal on bulk .223, don't hesitate to try it. You won't be able to tell the difference.