X Die .308

I recently changed from Lee dies to RCBS X-Die set for .223. I wasn't fond of the Lee dies, and I'm even less fond of trimming rifle cases.

I am just a few steps ahead of you in that I have done the initial trim on a dedicated batch of 500 cases. I have marked the heads so that I can keep them segregated for subsequent loadings. I'll see if the theory works in practice. Otherwise, the die will just be used as a traditional sizer.

My understanding of the benefits of the X-Die is not so much about extending case life, but in containing the growth of the length of cases so that trimming is not needed as frequently.

M1As are murder on cases. Best gains will be in setting the shoulder to the right length. Either way, I am not crazy about loading more than 5 time in M1A brass.

I have them for the 308 but have not shot it enough to know if it actually works. You are required to trim the brass below min spec if I recall, 0.010". This is the only time you should need trimming. Once you have the die set lock it down and do not touch. Should never require it. Just make sure you trim the brass as called for in the initial prep.

There is no specification for trim length. The suggested 10 thou less than max is an old rule of thumb now being posted in manuals for people who need assurance.

Head seperations can be nasty things. The only instructions I've seen for the X sizer is to trim back .030" from max to start and the bump on the decapping pin will then push anything longer than max back inside. I would toss any case that has grown 30 thou anyway so I have no use for such a device.

I've heard that the X die can bend case necks enough pushing them back into the shoulder bending it and bullet runout gets worse. I've not tested one, but someone who's got one could do a test.

No competitive shooter I know of uses one. Seeings how rimless bottleneck cases center in the chamber up front on their shoulder perfectly aligning with the chamber shoulder when fired, regardless of how much clearance there is around the case body, why would one want to push neck brass back into the shoulder possibly deforming that otherwise perfect shoulder?

They work very well for their intended purpose. As far as deforming shoulders etc, I have seen none of it. I am happy with mine and have them for both 223 and 308. I am not a match shooter and never checked runout etc in my 30+ year reloading life. My ARs are capable of sub MOA with the right ammo. I am capable of assembling the right ammo. I'm happy. YMMV