Case issue?

[Mechdraw]

Hi all,
An elongated explanation of my issue.
6mm Dasher, 40XBR action and local barrel(Aus)
Lapua 6BR cases false shoulder fire formed, after fireformed fits into chamber. Sized normally loaded with 2208(varget) Berger 105 hybrids. 005" out. No closing bolt issues.
Used another companies brass, seated projectiles same .005" out (these cases were sorted for weight and length to shoulder, chamfered and mandrel into neck before loading.) Closing bolt issues to a varying degree and showed on the target, verticals. I had about 80 new cases loaded for a prize meet unbeknown to me that some would fit and some not. Sorted all loaded rounds, 28 would chamber the balance not.
Decided to full length size the cases, but to what? They all fitted prior to loading. Checked seating depth again, same as the Lapua cases??????
These cases that did fit I fired and shot very well, the fired cases fitted into chamber, no issues. Sized and loaded, tight bolt. Lapua cases again no issues.
Anyone have similar issues? Or how to solve it?

 

[boltfluter]

Hi all,
An elongated explanation of my issue.
6mm Dasher, 40XBR action and local barrel(Aus)
Lapua 6BR cases false shoulder fire formed, after fireformed fits into chamber. Sized normally loaded with 2208(varget) Berger 105 hybrids. 005" out. No closing bolt issues.
Used another companies brass, seated projectiles same .005" out (these cases were sorted for weight and length to shoulder, chamfered and mandrel into neck before loading.) Closing bolt issues to a varying degree and showed on the target, verticals. I had about 80 new cases loaded for a prize meet unbeknown to me that some would fit and some not. Sorted all loaded rounds, 28 would chamber the balance not.
Decided to full length size the cases, but to what? They all fitted prior to loading. Checked seating depth again, same as the Lapua cases??????
These cases that did fit I fired and shot very well, the fired cases fitted into chamber, no issues. Sized and loaded, tight bolt. Lapua cases again no issues.
Anyone have similar issues? Or how to solve it?

I believe you answered your own question. Dimensionality there is something different about the other brand of brass. Time to break out the calipers. Neck diameter and dimension at .200 line would be the first things to check. Good luck and keep us posted.
Paul

 

[SteveOak]

Did you size the 'other' brass? It was new, unfired?

Who's brass?

 

[Mechdraw]

Boltfluter, yes I measured the brass but negligible differences, the brass hardness the only property unable to test.
Steve Oak, both cases, more than one piece, were sized with same die, but still bolt closure issues.
No issues at all with Lap cases, just the "other" brand.
Searching for any data on the differences between Lap and Norma brass to see if it sheds some light on it.

 

[NZ_Fclass]

Given that you have checked length to datum and neck diameter - I would be checking the size at the shoulder -ie diameter, on the chance that you have "squashed' the case during sizing/shoulder bump. Difficult to measure, but should show up as a bright line on the shoulder when run into the sizing die,

I had this happen to a few BR cases - Alpha brass - cured by annealing and resizing. Fired them with a jammed bullet to ensure chamber fit.

 

[Mechdraw]

NZ Fclass,
I have had some "bulged" at the intersection of body and shoulder but is noticeable and measurable which I think is due to overly soft brass, as I said earlier the hardness I can't measure. The bulge is measurable but the cases that when loaded show hard bolt closure but no bulge.

 

[Mechdraw]

it is bed time here so will continue tomorrow

 

[JGS_Jaz]

Searching for any data on the differences between Lap and Norma brass to see if it sheds some light on it.

Case length on the Dasher Norma is 1.605 and the Lapua is 1.570

 

[dellet]

A couple things to check, but first please clarify the brass. You had to fire form the Lapua 6 BR brass, but don’t mention doing the same for the new brass.
Are you using Norma 6 Dasher brass?

You don’t mention checking case length, did you?

A case with a longer neck, may fit the chamber without a bullet, when the case neck expands and the diameter changes, if it is a few thousandths too long for the chamber it will pinch in the transition from neck diameter to freebore.

One thing is certain, the measurements that you are assuming are a negligible difference, are not.

I would also check neck diameter multiple places.

Adding, apparently typing while jgs posting

 

[243winxb]

bulged" at the intersection of body and shoulder

Fix this.

 

[Ackman]

Case length on the Dasher Norma is 1.605 and the Lapua is 1.570

There's the answer. .035 is a lot.

 

[Mechdraw]

Morning All.
Just checked case length, Lapua fireformed 1.539" +-.002". Alpha brass, new 1.537" +.0035"

 

[Coyotefurharvester]

Color up one of the cases that don't chamber and find the contact problem.

 

[Mechdraw]

Yes I did that and it appears that the brass is larger in the body/shoulder intersection and when blackened in that area very distinct rub marks there. Fired brass is much larger there than fired Lap cases. I will have to change the way I size these cases and take particular note in that area.

Color up one of the cases that don't chamber and find the contact problem.

Thanks every one a great help, it appears I may have been given the answer.

 

[LRPV]

What are you using to seat your bullets? Does a fired and sized case fit without a bullet seated? I set up a “regular” threaded seating die (just the cheap RCBS 2 die set type) wrong, had it screwed in too far and it was trying to crimp the bullets but it was too much and I was collapsing shoulders while seating the bullets. Dumb mistake but it happens.

It was basically mushrooming the shoulder enough they wouldn’t begin to chamber.