Trim length of new brass?

[usma89]

I measured my lapua once fired brass. It ran an average of 1.550". The book states I need to trim it to 1.508". That is quite a bit of brass. Do I need to trim all of that off?

 

[Forum Boss]

Don't know what book you are reading. This is from our FAQ:

What is the Correct OAL for the Case?
New Lapua brass measures 1.556-1.557". SAAMI spec for the 6mm BR Norma case is 1.560". By contrast the OAL spec for 6mm BR Remington is 1.520". The Lapua brass is headstamped 6mm BR Norma-Lapua. We trim all our cases to 1.555" when any one reaches 1.560" or longer.

I suggest you fire your brass one more time, and then trim the minimum possible so that they all match. If you only have 2-3 cases which are quite a bit shorter, cull those and use them for sighters. It's best to leave the necks as long as possible.

I've gotten great accuracy with brass right out of the box which was not trimmed at all--just expanded and chamfered.

 

[Cheechako]

I believe the case length for the old original,1970s) BR was 1.5". That was in the days before BR brass was available and you had to make your own from the Rem Basic BR brass. You won't find many barrels that are still chambered for the original round and even the current Rem brass measures 1.55". I'd also be interested in what "book" made reference to a trim length of 1.508".

Ray

 

[usma89]

I got the data out of the VV powder manual. I only trimmed a couple pieces of brass, I will use them for sighters.

 

[buzzer488]

i did the same thing my accurate arms manual said trim 1.500..
will it hurt to shoot some of these shorter cases in a newer chamber?? i have since learned better lol

 

[memilanuk]

Good question... my two boxes of new Lapua 6mm BR brass are measuring around 1.554-1.555"... Sierra's latest manual gives 1.560" as max length, and 1.550" as trim-to length. I was planning on setting up my Wilson trimmer tonight and having at it... any reason why not?

Monte

 

[jb1000br]

Lapua's manual say trim to 1.551 -- wonder why VV would be different

JB

 

[Cheechako]

JB

I believe the VV manual is a typo. I looked at mine and the cartridge preceeding it is the 6PPC for which they also show a trim length of 1.508". Coincidence?? I also believe the Accurate Arms manual may be a typo since there are a lot of mistakes in it. Either that or they were still using specs for the old original Rem Br from the 1970s.

Ray

 

[buzzer488]

my 04 hodgdon annual manual also shows 1.510 would the short cases cause a lot of erosion??

 

[Cheechako]

I know the conventional thinking is that short cases will cause erosion of the front of the chamber but I wonder how true that really is. After all we are only talking about a few thousandths of an inch. And if you carefully measure most chambers, even custom ones like a 6 PPC in a BR rifle, you will find that most are longer than the brass most guys are shooting. IMHO short cases may cause a buildup of crud at the extreme front of the chamber but erosion? Most of my barrels are shot out before I worry about stuff like that anyway. After that they are used for live varmint shooting and those Prairie Rats can't tell the difference.

Ray

 

[buzzer488]

they do work great on rats

 

[Anmlsrdelicious]

FYI,,,,the lot of 6br Lapua brass that I have is measuring 1.563-1.565 straight out of the box.

 

[Dubya]

Just opened two new boxes and all measured 1.550 to 1.560.
Trim,after firing) to 1.550 and you should be good.
dubya.

 

[dreever]

From my personnel experience I feel that after about half a dozen loadings Lapua 6BR brass has grown to about 1.560 where it seems to stop growing pretty much.

If you have your chamber cut with a "no trim to length" of 1.564-1.570,6BR Norma)you can usually trim after the seasons over during the winter just to clean things up a bit before the next year. I have some Lapua 6BR brass with 23 loadings on it that I've done this with trimming to 1.550 once a winter. I think I'm going to toss it now, not because of any failures but just because it seems to be time.

I have a friend who wanted to see just how long his Lapua brass would last and he didn't experience his first failure till 74 loadings! I wouldn't recommend going that long, but it just goes to show you how long Lapua brass will last with safe and sane loads.

Danny

 

[6BRA]

My last box showed the shortest at 1.548. That's where they were trimmed. Ant then turned. You can't turn unless they all the same length. Well I guess you could..........

 

[Walt Krafft]

18 years and counting lol.

 

[Ned Ludd]

18 years and counting lol.

Resurrecting an 18 year old thread can be somewhat like finding a fossil. It may be old, but it still has a certain beauty that makes you want to keep looking at it.