case trimming tolerance

Bucksquirrely

Bucksquirrely

New member
I'm fairly new to reloading and was prepping some .225 cases this evening. I got it all sized, cleaned up and the primer pockets cleaned out and then went on to trimming the cases. My question is how many thousands can the case length vary? I set my trimmer up with one case and the next case came up about 2 thousandths short. And the next several varied from 3 thousandths under to 2 thousandths over, anything that came up more than 3 thousandths short I pitched. After doing 20 or 30 cases I got the tolerance down to between a 1 thousandths over or 1 thousandths under, so what is acceptable? And did I make a mistake pitching the ones that came up more than 3 thousandths short? Thanks in advance.


edit* I guess I could mention that I was cutting the cases to 1.920 and max length is 1.930
 
Yep, you made a mistake pitching the cases. You should have sent them to me! I do admire your efforts to get them as close as you can.

When your not crimping a case, case length is not critical if it's within +- .010 of the published trim length. Cases that are .010 under the trim length are still useable. In some long freebore chambers, cases .020 over the trim length are still OK. If you can hold +- .001, that's all you can hope for with most trimmers. My Lyman Universal has no problem holding +-.001 or .002 on most calibers. I try to keep all the same headstamps together in a batch. That way, they all tend to grow the same amount. I will trim them all back to the trim length when they get within .001 of the max or chamber length, if you know it.

If your crimping bottle neck cases, (which I don't) your crimp will be more unform if you can keep them +- .003.
 
Thanks for the input, I will be digging through the trash can tommorow for 5 cases. As far as the headstamps go, they all were the same-winchester super x, albeit about 40 of the cases(which were also the newsest ones)have a slight groove right below the rim, almost like a rimless case but not as deep, I'm not quite sure why its there, maybe to help the extractor seat further?
 
Great question as I was monder about this very same thing for my match ammo. I finally have my Hornady trimmer set up to trim Rem 308 cases within .001". I was going crazy there for awhile. Thanks Jim.
 
I generally keep all my cases in lots of fifty, once they have been sized, I carefully measure them and sepperate them short ot long,if they have been fired a few times they are never below minimum, I trim them all to minimum case length before I ever load new cases that way I start with everything even.
 
I was wondering if you measured the cases before chauffeuring the inside and outside of the case mouth? If you measured them straight from the case trimmer you could be hanging up on some burs, thus giving you different readings. I always clean the case mouth up before i measure them so i know exactly what my final product will be! My wilson case trimmer does not very and i really dont see why yours should ether no matter the brand. Some brands of case trimmers do not cut straight and this could also be another explanation. Now if you put both scenarios together then i can really see where your cases are varying a few thou apiece. Just my thought!! Lee
 
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