Am I wasting my time

[NSP64]

I load for 2 AR15's. Both are stamped 5.56.
I have been trimming my 5.56 brass back to .223 min case length.
Should I continue trimming or load then at 5.56 length?

I have no other guns that use .223
Thanks

[imashooter2]

There is no difference in case dimensions between .223 Remington and 5.56 X 45 NATO.

[303Guy]

But there may be chamber dimension differences. I would trim to suite the shortest chamber and check to see why the case lengths are growing.

[NSP64]

This is once fire range pickup . Once I resize it , it is over max length for .223?

[I'll Make Mine]

This is once fire range pickup . Once I resize it , it is over max length for .223?

Entirely possible; if it was fired in rifles with maximum tolerance chambers, the case may have stretched enough on one firing to go over max length (factory rounds are seldom trimmed to minimum). It's common to need to trim once-fired rounds, and case stretching is the commonest cause of case failure with rounds for a semi-auto that need to be full length sized for each reload.

[WineMan]

The 5.56 chambers are longer and have longer throats for heavier Ball ammo and longer tracer ammo. The 223 chambers may show pressure signs if used with the longer Ball and Tracer ammo. The trim to length is the same for both. Long brass in a short chamber regardless of caliber may be an issue. I do not think you would have a problem with too short (RCBS X-Dies trim less than the minimum for the initial prep) but too long in a short chamber with a hot load would be a concern.

Dave

[1Shirt]

I suggest you use only commercial brass, as I have had problems with Mil brass for 5.56 and no longer use it. I trim to min specs.
1Shirt!

[nicholst55]

I suggest you use only commercial brass, as I have had problems with Mil brass for 5.56 and no longer use it. I trim to min specs.
1Shirt!

Just curious, what problems have you experienced with milsurp brass? It's about all I use in .223. I routinely find that once-fired USGI brass exceeds the maximum length for .223, but I trim it to the 'trim-to' length listed in the book. Swage the primer pockets and you're good to go.

[Larry Gibson]

Get a RCBS X-die (the standard one; no need for the SB or "AR" one for 5.56 chambers) and you can FL size the cases for both rifles and won't have to trim anymore.

Larry Gibson

[Idaho Sharpshooter]

what Larry said, Plus One!!

[WineMan]

I like my X-Die but that initial trim on such a small case really had me worried. No issues so far and no trimming after three firings.

Dave

[Larry Gibson]

I like my X-Die but that initial trim on such a small case really had me worried. No issues so far and no trimming after three firings.

Dave

Most milsurp chambers will have longer necks than cases that have been sized after being just once fired. I do a cast of the chamber and then adjust trimming dimensions to the chamber's neck dimension, not to an arbitrary dimension. Thus with once fired 5.56 cases I adjust the mandrel to the untrimed, sized cases and have no problems. I've yet to lose a case to case head seperation since using the X-die. BTW; my X-die sized SP/HP loads are used in 3 ARs, 2 bolt guns and a Contender barrel.

Larry Gibson