Trim: Before or after sizing?

I trim after sizing as there may be some "elongating" or stretching of the brass during the process of sizing it. If you size before and there is a change in length as a result of sizing, this equals inconsistent shots or perhaps worse.
 
For better or worse, I trim after the cases are sized - I happen to use the Lee pilot and cutter system, which seems to be made to fit the "sized" inside of the neck - I suspected the idea was to make sure the case does not run into the end of the chamber cut-out, and I know some cases that I sized got "longer" by doing so, so my idea was that if case length is critical or important, then to set it after all the other "work" on the case had been done.

I have never loaded hand gun rounds, and never had to trim 45-70 when I had one, so my only experience is about bottle neck centre fire rounds - might be different with straight walled stuff - I wouldn't know.

For a while, I was interested in crimping bullets - I found that case length trimming almost a necessity to get them even, to be able to set the seating die to do a roll crimp into a cannelure. Hence, again, made sense to trim once all the sizing was done. I have since given up on that - I now just trim because of chamber length - no other reason...
 
The only time I’d ever trim before is if I for some reason had a batch of mixed or unknown firing brass that was intended to be used for precision long range loads. I’d maybe check for abnormally long stuff and knock it down a bit before the sizing process in the interest of keeping the sizing operation consistent. It may not seem like much, but .020” longer than the average will potentially throw off your annealing and full length/neck sizing.
I’ll always trim again after sizing as that’s the proper order.
 
After sizing. You want the real case length in the condition that it will be chambered.
This will also limit variances specially if brass was from somebody else rifle, once fired ect.
 
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