case trim tollerance

thorborg · Jun 30, 2016

Having neck sized only all my life I now find that case specification reading leaves me wanting as it applies to full length sizing.
within the many manuals all the specs are absolute and devoid of tolerances.

45-70 case length reads 2.105 on the spec sheet.

Is this the max?
What would be the minimum?
if it is max, hitting a spec to .001 every time may not be realistic in my trim production unless I spend much time and expect wastage, so I would like to shoot a couple grand lower to allow some breathing room.
What sort of tolerance do reloaders generally apply to trim length and does it apply to all calibers?
I ask about "all calibers" as 45-70 for sure is a forgiving caliber and not atypical.
Thank you kindly for sharing your experience.

deadeye · Jul 1, 2016

2.105 is the max according to the speer book, the trim-to length is 2.095.

You may want to buy the speer book as it states max and trim-to but most are a .01 NOT .001 difference between the two.

xlsbob · Jul 1, 2016

I have Starline 45/70 brass that I have loaded 20 times without being trimmed. Without changing settings on the dies, the crimp groove on the bullet still ends up in the right place on the brass so I'm guessing the brass doesn't stretch much.

ChiefStealth · Jul 1, 2016

SAAMI specs for 45-70 are max = 2.105 min is 2.085
For every cartridge there is a SAAMI min. and max. just look them up.. easy. Anything within the range is correct. Now, as for preference for trim length... for rifle cartridges I typically trim to .005 to .008 less than max. I don't worry much about the exact length. Just as long as it is within the range. I can't be exact to .001 all the time. Not trying to be. I have no need to be that exact.

Member 5605 · Jul 1, 2016

Typical trimming is maximum length -.010"

.223 states 1.760"
I trim to 1.750" +/- .001"

A little different for some calibers like cannons.

thorborg · Jul 1, 2016

Thanks, This clears the fog.
Used lee hand loaders for 45 years for seven hand and rifle calibers and with neck sizing, never seemed to stretch cases much and annealing not needed also. I'm fair at tempering and heat treating so annealing shouldn't be an issue.
I bought a press to reform some brass to shoot things I couldn't get ammo for and thought I would first start moving brass on things I was already comfortable with.
Full length sizing of 45-70 brass lengthens my cases by .006 - .008 which pushed them cases to 2.108 (.003 over) surprising me. So I picked up a Hornady hand crank and that's how I got to my question.

One more question if you please, Heat can do strange things to metal so I'm wondering if I should anneal the reworked brass before I trim? (it would definitely cut a little easier) or is the potential growth from heating insignificant?
Thanks again for your help