Acceptable case length variance?

I just opened a 50 pack of 45-70 Starline brass and measured their lengths, and was pleased to find they were much more consistent in length than the R-P that I used earlier.

The Starline measured:

2.097 11 pieces
2.099 29 pieces
2.100 10 pieces

(I measured with a caliper and grouped by rounding up the .0005 to the next thousands when separating them)

I don't have a trimmer yet, but was thinking of either just using the 29 2.099 cases for now, or perhaps blending them and the 10 2.100" cases. This would actually result in almost a .002 spread in case length -- is that too much to get reasonably consistent crimping?

Guess it boils down to "how much variance in case length is acceptable?"

Thanks,

Randy

I would question as to whether you'd be able to discern any difference (in crimping or accuracy) with 0.003" spread in length.

Crimping and accuracy don't necessarily go together well either. That is to say that taper crimping should give you better accuracy as well.

Thanks - would I be able to keep the crimp in the groove with that much spread though?

While I'm on the topic of crimping, why do some seat and crimp in two separate steps?

Randy

ghh3rd, some people like myself seat with one die and crimp with another to get better results especially when using a taper crimp die. Most of the time I use the taper crimp die to make sure they are no burrs on the case mouth when loading for semi-auto guns. The .003" difference in your case length is no bad, I would be more interested in the case weights for accuracy.

some seat and crimp to keep the case from buckeling just under the boolit. A boolit that fits tight, if you seat and crimp in one step, you are VERY likely to buckle the case. Especially in 45-70 cases. i would not worry about a .003 vriance in case length. Even my hornady case trimmer will vary cases around .002. If you are loading for a single shot, do not crimp. You will kick yourself.

If you are loading for a single shot, I agree, do not crimp. If you want to trim but have yet to purchase a trimmer look into an RCBS file and trim die.
Regards,
Tony

That variance is pretty small. You'll not likely be able to discern any variance while crimping or shooting. .003" variance will not cause a mismatch with virtually any cast-bullet crimp groove, and truthfully, you'll be hard-pressed to even discern it at all with your eyes.

I seat/crimp as separate steps. Takes more time than combining the two steps, but sometimes it makes a noticeable difference in the quality and uniformity of the crimp. Good luck.