Brass Expansion

[Taylorbok]

The neck diameter on fired brass is 0.268". The brass would have had some spring back from say 0.269". The maximum neck diameter on the chamber spec is 0.267"

The diameter of the brass body by the shoulder on fired brass was 0.267". The drawing of the chamber spec shows a maximum of 0.263".

I think ur looking at the wrong drawing. Even the one you posted shows .277" neck Diameter +.002" tolerance.

It hangs up about .040 from the case body. It'll go in so far, but expansion at the body/ shoulder junction stops it. Therefore there is no way to measure shoulder bump short of resizing long and working back.

I think ur using the wrong comparator. You should be using the .400" comparator. If that won't go over the neck there is big issues.

 

[Taylorbok]

Bushing with mandrel. ID after sizing is .240 giving me .003 neck tension. So, brass thickness is about .013 on the neck.
.240+.013+.013 would give me the .266.

Fired brass will not go into the head space comparator. It is too expanded in the shoulder area. I haven't seen that before either.

What does the neck OD of a loaded piece of ammo measure?

 

[ShtrRdy]

I think ur looking at the wrong drawing. Even the one you posted shows .277" neck Diameter +.002" tolerance.


I think ur using the wrong comparator. You should be using the .400" comparator. If that won't go over the neck there is big issues.

Oops! Thanks for pointing that out. I corrected the post. Must not have had enough coffee yet.

 

[Philward]

Ok, it must be a comparator that the whole case slides into, like the rcbs one I have for 270.

 

[Mickp7]

If it's Hornady or similar it might be the wrong comparator in use. No where near datum diameter.

SAC, 6mm x 30 degrees

 

[slikmrc]

I'm in the process of loading 6 CM Peterson brass, once fired. Using a Forster die with necked honed to .268, bumping shoulder .001. Fired neck OD is .275, sized neck is .271, loaded neck is .2715. Fired shoulder/ neck OD is .462, sized is.458. Looks like your chamber is big at the shoulder/neck OD. Hope this helps.

 

[Philward]

SAC, 6mm x 30 degrees

I went and looked at the SAC design for the comparator. I can see where their tapered design can be an issue if your chamber is too large and you're measuring the fired case and then the sized case. Don't think it's the body/shoulder junction that stops it but the neck/shoulder junction probably is. The body/shoulder junction should never contact the tool. Try a comparator that doesn't have the tapered part and you can probably get a measurement. Good luck to ya.

 

[Mike D Texas]

The neck diameter on fired brass is 0.268". The brass would have had some spring back from say 0.269". The maximum neck diameter on the chamber spec is 0.277"

The diameter of the brass body by the shoulder on fired brass was 0.467". The drawing of the chamber spec shows a maximum of 0.463".

His fired diameter is .278, not .268. That might be .001 over after spring back but doesn't seem excessive.

I didn't look at the shoulder diameter. So you may be right but that's a LOT of reamer wear. Maybe not bored concentric?