308win trim length question

[ubet]

I trimmed a bunch of lapua 308win once fired brass. And going through case gauging and measuring case lengths. I am throwing everything that’s 2.007-.008 into the use bin, stuff linger in one shorter in another. My question is, how much of a difference does .001-.002 in length make on 308 accuracy and velocity wise? I’m at best average shooter. And just do it for fun.

This is a string from this brass when it was new for reference.

 

[FredHammer]

Doesn't matter, unless you want brass to crimp into a cannelure or copper mono band consistently.

 

[Shoots 700's]

Load it and stop the worry

 

[Baron23]

how much of a difference does .001-.002 in length make on 308 accuracy and velocity wise?

None…you are talking less than the width of a hair. Think about it.

 

[Robert4]

A 308 case neck is about .260" long so even .010" variation is only about 4% of that length. Even .002" is less than 1% if the neck length, insignificant in my opinion.

 

[diggler1833]

Not going to adversely effect your accuracy or velocity unless you are in a strict benchrest or LR discipline. I've had several .308s in my life that shot very well with worse brass than Lapua, and trimmed to 2.005 +/- .003.

 

[ubet]

Ok, thank you. Most of it falls between 2.006-2.010. So I am guessing that's "good enough"? It is easy to get lost and not see the forest through the trees sometimes.

 

[Dolomite]

You can probably let it grow longer to 2.015. Check the longest case against the end of the chamber using a bore scope or the Sinclair chamber length tool. The book suggests trimming cases really short which leads to carbon rings.

 

[memilanuk]

IIRC the default end of the neck area extends as far as 2.045", so you could - in theory - let the necks go almost indefinitely, depending how much growth you're seeing per firing.

That said, I've shot a pretty fair amount of 308 over the years, and I've never seen anything even close to a carbon ring forming. Not saying that it can't happen, but if I had to pick a caliber where I'd be worried about that... the 308 Win would be pretty damn low on that list.

 

[Doom]

The chamber dimension breech face to end of case/neck is 2.025".

 

[memilanuk]

The chamber dimension breech face to end of case/neck is 2.025".

The print I have for the 2013 US FTR team reamer - which was derived from the 1995 US Palma reamer - shows 2.045".

Maybe they stretched it out from the SAAMI version?

 

[Doom]

The print I have for the 2013 US FTR team reamer - which was derived from the 1995 US Palma reamer - shows 2.045".

Maybe they stretched it out from the SAAMI version?

Apparently.