Norma 6XC Brass Dimensions

[Bob3700]

ALL,

I am loading the new Norma 6XC brass and have taken a micrometer to compare it to the older Tubb brass and the reformed 22/250 brass.

Have noticed two differences in the Norma brass:

1) Diameter of the brass just above the rim,case head) is .002" larger than the Tubb or 22/250 brass. Norma measures .468 vs .466 for Tubb and 22/250.

Don't know if this added diameter will affect extraction, especially in a bolt gun.

2) Neck diameter of a loaded Norma round,107 SMK) is about .002-.003" larger in diameter than the Tubb or 22/250 brass. Loaded neck on the Norma is .271 vs .268 for Tubb or 22/250.

Have any of you found this change in dimensions to be an issue? I am only using the Norma brass for slow prone fire and there it should not be much of an issue for me,AR10 here). My rifle is sizing the brass at the head of the case when the carrier chambers the round. You can see the obvious scuff marks at that point.

A bolt gun might be a different story.

Bob

 

[Jefhai]

Based on the original reamer specifications you should not have a problem. I measured some 2nd & 3rd generation,unfired) Tubb brass and was the same as yours.

The new Norma/ Tubb is generally .002 thicker than the old Tubb.
My Norma/ Tubb measured just above the rim at .468 like yours. Twice fired and sized its at .470 with no chambering concerns.
The extra meat can only benefit brass life and pressure.

I run Sierra 107's and Lapua 105's and get the same seated measurement as yours. In fact I have seen an improvement in shot group with a little tighter neck tension.

As far as firing it thru a black rifle if you see or experience any chambering problems -try turning the sizing die in more and let it cam over a little more, while unscrewing the bushing adjustment. This way you will headspace safely and obtain the same head to shoulder length while sizing farther down the case body.

The scuff marks are probably inherant with the high speed locking and un-locking of the AR bolt. I bet thats fun to shoot though with the mild recoil?

-Jeff

 

[Shiraz]

ALL,

I am loading the new Norma 6XC brass and have taken a micrometer to compare it to the older Tubb brass and the reformed 22/250 brass.

Have noticed two differences in the Norma brass:

1) Diameter of the brass just above the rim,case head) is .002" larger than the Tubb or 22/250 brass. Norma measures .468 vs .466 for Tubb and 22/250.

Don't know if this added diameter will affect extraction, especially in a bolt gun.

2) Neck diameter of a loaded Norma round,107 SMK) is about .002-.003" larger in diameter than the Tubb or 22/250 brass. Loaded neck on the Norma is .271 vs .268 for Tubb or 22/250.

Have any of you found this change in dimensions to be an issue? I am only using the Norma brass for slow prone fire and there it should not be much of an issue for me,AR10 here). My rifle is sizing the brass at the head of the case when the carrier chambers the round. You can see the obvious scuff marks at that point.

A bolt gun might be a different story.

Bob

I changed over to the new Norma 6XC brass and found that the cases would not extract. Will have to hone the extractor claw a bit. It's a Nesika action.

 

[aubrey]

On brand new unworked Norma cases, I've been getting bolt stick at the top of the arc just before it unlocks,T2k). Not too much, but enough to break the rhythm of the bolt action.

I think a combination of resizing and case trimming may solve the problem, I've yet to verify this.

Aubrey