Why is Lapua 6mmBR brass .004" over max in case gauge?

[Clark]

I have 100 pieces of Lapua 6mmBR brass that measure .004" over max in my Wilson case gauge.
I have 1200 pieces of RP 6mmBR brass that measures .000" over max.

TIA
Clark

 

[mikecr]

What does it measure after fire-forming?

 

[Clark]

The old used Rem700 that I put an old used Krieger take off on, and cut the threads and chamber, I used a piece of Lapua brass as the headspace gauge.
As you can imagine, any brass that is fired in that gun is +.004"

 

[DCRYDER]

Is your case gauge for a 6mmbr Remington or a 6mmbr Norma? May be the difference.

 

[Clark]

The Wilson case gauge just says "6mmBR"
How can we find out if there is a difference?

 

[cliffy]

Even .223 Remington Lapua Brass is TIGHT in shell holders. Somehow Lapua is bigger in several dimensions over most other brass. I'd ask Lapua why this is, but I prefer Remington brass that slickly fits and remains easy to size - trim- shoot. Cliffy

 

[fdshuster]

Clark: I personally have no use for Wilson case gauges when it relates to my 6ppc, 22BR and 6BR's(4). They are all custom chambers, and my only concern is, how the Lapua brass fits in the chamber(s). My standard procedure is to take a fired case as it comes out of the chamber, clean it with a light hand polishing, hand punch out the primer, take all critical dimensions, and set-up my Redding Type S neck bushing die to duplicate those dimensions. Have several case gauges for other "standard" ctgs. ( 223, 308, 30-06, etc.) and have not used them in many years. My rifle chambers have become my "case gauges".

 

[SmokinJoe]

To add one thing to fd's comments. Get some of those little inserts from Sinclair's for measuring chamber OAL, and check that dimension, too. Sometimes it's surprising what your chamber OAL actually is. This gives you a true measurement to base your trim length on (chamber OAL minus .015" or so).

 

[KevinThomas]

Clark,

What are we talking about here? The length of the cases, or the headspace dimensions as they relate to the gage. Frank's already touched on this nicely, but I'd like to know precisely what we're talking about here.

Thanks,

Kevin Thomas
Lapua USA

 

[Clark]

What is the registered headspace dimensional tolerance range for the cartridge? and what for the chamber?
I only have SAAMI drawings through 1980.

 

[mikecr]

If your trying to use new, unformed brass, as a HS gauge, then I guess your chamber is truly custom(better cut your die blanks as well).

Either way, if you fiire-form the brass, it will be perfect for your chamber, however you made it.