Forster Case Trimmer - tips?

[Tudenom]

Hey guys

I'm having some real trouble getting my 38 special brass trimmed to the same length with my forster trimmer. I'm using the correct pilot and the collet holds the brass easily. I'm placing the brass in the collet, running the cutter up with a little tension and then tightening the collet to make sure the case is square to the cutter. Everything is clean and oiled properly, no brass shavings getting stuck anywhere. I'm using a hand drill to turn the cutter with the proper adapter.

I don't use mixed brass and load in batches with all the same headstamp. I've used three different beands and still have the same issues with inconsistent brass length.

As far as I can tell everything is working properly, and yet I'm getting variances of 30 to 40 thou in my case lengths and it's throwing my handloads off.

Am I doing something wrong?

Will small variations in the rim diameter cause this issue?

 

[jdman]

Measure a few before you trim them, i bet the differences, are that the brass is already shorter than what you are shooting for to start with.

On a side note, i have never ever trimmed any pistol brass.

 

[Eduardo]

Hi Tudenon,

I also never heard about trimming pistol cases, what is this 38 SPL for? Sorry I'm just curious, is it for handgun or rifle?

 

[Tudenom]

I'm reloading 38 specials for my lever gun (cowboy action shooting) that's chambered in 357 mag. Since it's a tube fed magazine I have to crimp the bullet.

I've been measuring the brass after its been sized and then setting the length on one of the shorter cases and discarding the super short brass.

I'm finding that the less I pay attention to the case length the wider the groups, factory ammo (three different brands) shoot about 2" groups at 50m, decently trimmed brass about 6" at 50m and badly trimmed brass at 20" to 24" at 50m. The poorly trimmed brass is hard to keep on the old IPSC target backer board I'm using to tack my targets to.

I'm getting super wild fluctuations even with different powder and different bullet combinations and the only remaining item that I can't account for is the crimp.

BTW - I've tested combinations with no crimp at all and have seen improved group sizes as compared with crimped.

 

[Griffin6869]

I have never trimmed any of my pistol brass as well But I have only used them in pistols - I get great results with a 158Gr swc and w321

 

[Tudenom]

Okay, I'm embarrassed. I've been reading my digital calipers wrong! I've been reading 10 thous as thous making it seem like brass is out 30 to 40 though but it's not.

Out of 15 measurements the vast majority are within 1 thou with only two longer and one shorter, so it's not my case lengths causing the problem.

I'm still not sure what's causing the erratic behavior of my hand loads though and why non crimped loads are performing so much better than crimped loads. Inconsistent crimp pressure maybe?