Let it grow, let it grow, let it grow...

[TommyD11730]

Hey guys I'm wondering what's everyone's procedure for trimming brass. Now just so their is no misunderstanding I'm talking about the overall case length.

In the past after setting my shoulder bump I would trim all cases back to the length that Lapua manufactured them too. If nothing else it kept me from "guessing" and at the end of the day every piece was the same overall lenght. (After resizing fired brass I had too much variations case to case and by too much I mean more the 003").

Then I got to thinking. Man I'm trimming each fireing, am I streaching/overworking my brass?

So, I buy a chamber gauge ( you see where I'm going) and measure the chamber.

2.055

That's a heck of a lot deeper then the 2.008 I have been timing them too.

So my question is going fwd do I disregard uneven OAL after resizing and just monitor growth after resizing?

Thanks Guys

 

[sinister]

I trim so that each and every case is the same length.

It's up to you and your rifle's preference to figure out what that base length is. It may be longer or shorter than factory.

 

[bax]

Assuming that you are full-length sizing, there are case trim objectives:

• consistent length
• consistent neck tension
• don't hit the end of the chamber

Suppose that neck thickness is always the same (not necessarily true) and therefore neck ID is always the same. Two given cases with the same overall length will have the same neck length and the bullet will experience the same tension as it is being forced into the lands. If one case is 0.010 longer than the other that case will exert tension longer (because the case itself is longer) and there will be more work to get past the tension. If one case has a thicker neck than the other, the extra brass will increase seating force and neck tension. Yes, you can neck turn but it is a PITA. Better to buy good brass and avoid the problem.

Speaking for myself, I ignore neck thickness - its just too much trouble to fix so I use good brass - but I control neck length and tension by

• anneal every time
• get consistent shoulder length
• using an expander to set the neck ID
• I trim every time to about the same length - for 308 I trim to about 2.010

I get pretty consistent seating force. While seating I hand sort the "hard seaters" and put them in one end of my loaded ammo box. I think that "hard seaters" happen when the annealing is insufficient (so the neck is still hard) or when the neck thickness is greater because brass is flowing into the neck - "dreaded donut".

So, get consistent shoulder length and trim to get consistent neck length. If after that you still have notable seating force variation, anneal and use an expander.

As with all things reloading -- YMMV.