After You've "X" Died Your Rifle Brass a Time or Two...

[DamnedDirtyApe]

.... what then? I've got some 4 or 5X fired .308 for my M1A that I ran through a small-base RCBS X-die after under-trimming them by .020.

They've shot themselves out to average about .010 under trim length after firing them. Do I trim them back to .020 under again, or leave them be? They are still within spec for reloading.

They are inconsistently sized now, some are .010 under, some are close to recommended trim length, etc.

I thought the X-dies were supposed to largely eliminate trimming. I'm confused.

 

[bogie]

You're thinking too much.

Pick the smallest length, set your trimmer there, and trim 'em all. Then put the trimmer away.

 

[Steve in PA]

After trimming and X-die-ing .30/06 brass for my M1, I've never had to trim again. They have several firings through them. If you read the info that comes with the die, I believe it says that after the initial trim, the brass may grow a bit but settle in with no need for additional trimming.

 

[Rico567]

When I first acquired my X-die in .308, I took a lot of new cases and loaded half the conventional way, and half with the X-die (after trimming, of course). After several firings of both, the former are growing in length as would be expected, and the X-die trimmed cases reached a constant length, and now get no longer (once again, as would be expected from RCBS' literature). As long as your cases don't exceed the max case length given in your manual, I see no reason to worry about it.

The theory is that the mandrel in your X-die will prevent the case from growing beyond the length at which the mandrel is set. As long as the mandrel is not moved, I see no way that the case length can grow beyond that point....unless I have somehow misunderstood the operation of the X-die.

 

[moredes]

You're in 'bolt gun-mode'. What Steve said. (I think) X-dies are much more useful with semi-autos than bolt gun ammo.

The whole point of the X-die is to eliminate trimming. Initially, you should have trimmed to 1.995"; after the 6-7th firing, the overall case length should measure in the 2.005- .007" range, and you should top out at around .008-.009"; at least, that's been my experience. And 2.015" is the cutoff.

Sure, 'accuracy' is influenced by the ability to control consistent case length, charge weight, bullet seating depth, etc. ad nauseum....but your biggest hurdle in setting the OAL (to the ogive) is dictated by the magazine's dimensions. Bolt guns will allow you to influence accuracy by sorting according to consistent case length, but your "battle rifle" won't notice that much of a difference.

 

[Kamicosmos]

So it appears to work! Excellent! I have been debating on getting one for my AR for a while now. Looks like it might have to be included in my next midway order...

 

[DamnedDirtyApe]

So, I'm guessing, I should just leave them be while they're still within reloading specs, even though they're inconsistently sized?

Thanks for the replies, all.

 

[444]

I would like to hear more about this, since ONE of the reasons for trimming cases is to have them all the same length. If yours arn't all the same length, I would trim them, X-Die or no.

 

[Steve in PA]

I'd leave them alone, unless you are crimping the bullet.

If your not crimping (and there is really no need to crimp), the neck tension will hold the bullet and your rifle won't know the difference.

 

[30Cal]

How are they inconsistantly sized?

If you followed the instructions they should all be pretty much the same length. After you trimmed them initially, you should have sized one, then cranked the mandrel down on the X-die. From experience, they shouldn't be growing by more than say 0.003".

Ty

 

[444]

I feel pretty strongly that your rifle WILL know the difference.
I have never conducted A-B experiments, but others certainly have. Trimming your cases to the same length is a standard procedure that has been done by the best shooters in the world for many years. Very few people question it.

 

[moredes]

I'll go agin the flow with these two comments, but it's the best advice I can give.

Crimp. No two ways about it. If it was a bolt gun that you were loadin' one at a time, sure, no crimp is okay. Since this discussion was brought up in order to figure out the trimming requirements when using an RCBS X-die for reloading M1A ammo, I'll stand by "Crimp". There's only one exception---if you never plan to load 2 rounds consecutively from the magazine, you're safe not crimping your ammo. Accuracy is one thing, and will definitely be affected if your bullets reseat during chambering. However, if your necks aren't crimped, and the bullets get seated real deep, you'll increase chamber and port pressures, possibly to dangerous levels. There's also the possibility that higher port pressures, though not dangerous, will be high enough to batter your action or total out your op rod. Crimping can also increase pressures to dangerous levels if taken to extremes. Crimp only enough to hold the bullet in place. One way to test is to see if you can adjust the seating depth of the bullet by pushing the bullet against something like the side of a table. Moderate pressure shouldn't change the bullet seating depth; only crimp enough so that the bullet is held in place even with 'moderate' finger pressure. If your loads feed well, AND don't change OAL when you try this test, you can avoid crimping.

Secondly, accuracy might be impacted by allowing variable overall case lengths, but if your M1A is demonstrably effected by different case lengths within say .003 - 006", that's one finicky M1A (target gun) you've got. 1/2-MOA M1A's are pretty rare....sure they'll shoot the odd tight group at 100yd, but a true, consistent, 600yd, 5-shots-1/2 MOA M1A is a rarity...that gun might actually show you how much accuracy is lost *just* because your brass isn't consistent. But I'd bet RCBS will tell you to X-die your brass once and leave it alone; I'd also bet any of the major bullet manufacturers will tell you that .003-006" variation will not influence your accuracy noticably in a semi-auto, unless you're David Tubb.

Lastly, if you're gonna trust the logic of RCBS's X-die, why buy it if you're gonna continue to trim? The whole point of the X-die is to enable the reloader to avoid trimming. You want great accuracy, trim for your bolt gun and leave your M1A (or any other semi-auto) for 'play'.