The factory Winchesters were ave. 2.834
My question is, do I trim back to 2.850 or slightly less as with the factory case.

Some of the cases that I am trimming are in the 2.875 and one was 2.881.

All my manuals list the trim length to 2.840 and thats where my trim die is set. Always worked for me.

Joe

I also trim to reloading manual specifications.

Harold

Why not measure your chamber length and put your mind at ease?

Ray

All the data I have found so far says factory spec on COL is 2.850. Did I hurt my brass trimming it back to the 2.834 that was the average length on my brand new Winchester brass?

I have not had any problems with the new brass but was wondering if I am allowing my brass to run/flow to much and shorten the brass life.

I am loading up 78.5 grns of IMR 7828 under a 150 grn SMK. This is producing 1 1/4" groups at 200 yards for me now.

quote:

All the data I have found so far says factory spec on COL is 2.850. Did I hurt my brass trimming it back to the 2.834 that was the average length on my brand new Winchester brass?

You didn't hurt anything. Many of my cases are fireformed and end up about .05 short to begin with. I will often shorten factory brass that amount and not worry about triming. Cutting the neck a little shorter will not cause the neck to stretch more(at least not in my finding)

Key issue to magnum case life is to switch to shoulder headspacing after the first firing and then bump the shoulder only enough to allow smooth chambering.

Do I just bump the shoulder with a neck sizing die or a FL die. Is this more of a feel thing when setting up the die?

A neck sizing die won't bump the shoulder. If you are only neck sizing then you arn't setting the shoulder back which is good. Normally after a few firings neck sized brass will get hard to chamber as it gets to be a tighter fit. When that happens you use a FL die to bump the shoulder back.

Since many of rounds I reload are my wildcats I use a fl die. I set the die up to bump the shoulder back a couple thousands. Then slip a shim under it so I normally just neck size. I used to move the adjustment ring but I kept forgetting if I had returned it or not.