Brass differences in 5.56/223 Mil vs Comm

[thunderbolt]

I've been reloading R-P brass in my 5.56 AR for a while now with great success and now I want to load the rest of my collected brass which is a mix of LC, Win, and PMC. Most of the LC came from Mil surplus and I've been told that, aside from the primer pocket, the brass is thicker which requires a reduction in powder charge.

The thing is, I took a casing of each headstamp and cut them in half measuring the thickness. The comm casings ranged from .030 on the base to .010 at the neck. The mil brass ranged from .035 to .010. Is that enough to push the pressure pass the safe? My rifle likes 26.1g of Varget behind a 55g FMJBT by the way.

[Antihero47]

5.56mm military brass is OK to use loads interchangeably.

7.62x51 and possibly 30-06 military brass has thicker webbing and loads need to be adjusted.

[freonr22]

May not answer your question at all but here is one thread I made.

http://www.calguns.net/calgunforum/showthread.php?t=227394&highlight=Brass

And Randall's data sheet may give more I site specific to your questions

http://ar15barrels.com/data/223weights.xls

[freonr22]

Also if you are significantly changing internal volume, you are gonna have to work up an adjusted load

[GeoffLinder]

Weigh them, if they are within a grain or two of other cases they are interchangeable.

.223 and 5.56 cases are identical externally, it's internal wall thickness and web construction that vary, if they weigh a lot more (2.5gr or more) than other cases you are using then they have significant internal volume reduction and will need a slight charge reduction if you are loading to the max. If you are loading conservatively to start pressure-wise then most any case weight variance will not be an issue.

Case wall thickness measurements will not tell you as much as case weight comparisons will here