300wm excessive headspace?

[D̷e̷v̷i̷l̷D̷o̷c̷A̷Z̷]

Got a rifle second hand, unfired. Schultz Precision did the work, not trying to badmouth them, but not looking to protect them either. Idk them at all.

Took it out and while it shot really well. The trouble occurred when I got home and inspected the fired brass. If you zoom in and look at the belt towards the case mouth you will see a “ring”

I don’t know shit about fuck when it comes to 300wm.

I’m not “looking” for problems, I just don’t want to ruin all my brass.

I measured the brass w the Hornady device collet E.

Fired: 2.283”

Un-Fired: 2.256”

Growth: 0.027”

 

[supercorndogs]

300wm headspces off the belt, so you almost always see lots of shoulder growth. I think Peterson is the company that makes 300wm long brass, which fills the chamber better. That said I have never had 300wm brass come out of the chamber looking like that right a above the belt. I would be contacting the builder.

 

[pabrousseau]

Possibly spot where case web ends and case wall expands. Same as we see with non belted cases when fired in a chamber with greater diameter than the case head. Take a few cases and fire them several times and see what happens.

 

[pabrousseau]

Cut a case in half or try to measure from the case mouth to the web on the inside of the case.

 

[WB300]

Take the worst looking one, cut it in half lengthwise and see what's going on..... and include a pic.

 

[supercorndogs]

300wm headspces off the belt, so you almost always see lots of shoulder growth. I think Peterson is the company that makes 300wm long brass, which fills the chamber better. That said I have never had 300wm brass come out of the chamber looking like that right a above the belt. I would be contacting the builder.

You probably have excessive head space. The mark above the belt is likely where the chamber is cut too deep, which is causing the expansion above the belt. If you have a belted mag field gauge you toss it in there, but I bet if you show these pictures to the builder they will want it back to fix it.

 

[918v]

Yeah, the shoulder length growth is pretty long. That ring above the belt is weird too. It looks like the brass was roll sized. I get that mark from my roll sizer after 6-7 reloads. But you don’t even have one?

In my 3 rifles the shoulder grows close to .025”. I can still get 15 loads out of Hornady brass so it’s not as big of a deal as people make it out to be. Just bump .002” and you should be ok.

 

[FredHammer]

I'm sorting out a problem as we speak with a 300WM. I think 300 PRC is the answer and fuck them belts.
.027" shoulder growth is pretty long. Typically see 2.270-73. SAAMI datum line is 2.270.

 

[supercorndogs]

That growth is pretty normal for a belted a mag for the reasons in post #2.

The shoulder on the brass in both of my 300WM barrels moved about that much also. I also took some of the Winchester brass I had for my first barrel to 15. It looks like it is still useable, but i don't shoot that much 300wm anymore and started with new brass on my new barrel.

Have the cases in the photo been sized? Its not the die rolling brass to the bottom is it? It comes out of the chamber looking like that correct?

Thinking about is I am not sure I would expect such a sharp edge if it was a false shoulder from firing it once. I had a small base die that would roll brass up like that on 6.5 Grendel cases.

 

[918v]

I'm sorting out a problem as we speak with a 300WM. I think 300 PRC is the answer and fuck them belts.
.027" shoulder growth is pretty long. Typically see 2.270-73. SAAMI datum line is 2.270.

300WM has been around forever. These “problems” aren’t really problems.

 

[918v]

Maybe that ring above the belt was there pre firing?

 

[D̷e̷v̷i̷l̷D̷o̷c̷A̷Z̷]

That growth is pretty normal for a belted a mag for the reasons in post #2.

The shoulder on the brass in both of my 300WM barrels moved about that much also. I also took some of the Winchester brass I had for my first barrel to 15. It looks like it is still useable, but i don't shoot that much 300wm anymore and started with new brass on my new barrel.

Have the cases in the photo been sized? Its not the die rolling brass to the bottom is it? It comes out of the chamber looking like that correct?

Thinking about is I am not sure I would expect such a sharp edge if it was a false shoulder from firing it once. I had a small base die that would roll brass up like that on 6.5 Grendel cases.

Only been fired.

Factory Berger ammo.

 

[D̷e̷v̷i̷l̷D̷o̷c̷A̷Z̷]

Maybe that ring above the belt was there pre firing?

Fired on left of pen, virgin on right.

 

[918v]

It looks to me like the ring is caused by the chamber. Maybe they reamed the chamber in 2 steps, first the body/neck then the belt for headspace.

 

[msgriff]

I'm going to add a couple drawings for quick reference

Cartridge:

Chamber:

 

[FredHammer]

300WM has been around forever. These “problems” aren’t really problems.

It was both a joke and an excuse to get into another cartridge.

 

[Rocketmandb]

Someone else said it:

Cut two cases open with a Dremel or hacksaw - one unfired, one fired - and compare. Post pics here.

It almost looks like the belt moved. Would be interesting to know what that measurement is from the mark to the belt.

 

[supercorndogs]

Just me, but I wouldn't be trashing two peices of 300wm brass just to see what it looks like inside. The brass isn't the cause.

I'm going to add a couple drawings for quick reference

Cartridge:

Chamber:

To simplify or interpret the drawings brass minimum is 2.27 minus .007 so 2.263 min.

Chamber spec is 2.279 plus .01. So max is 2.289 for the chamber.

 

[918v]

It was both a joke and an excuse to get into another cartridge.

Yessir

 

[OkieMike]

According to Peterson, if you fire SAAMI Min. brass in a SAAMI Max chamber your brass can grow up to .026" so jumping well over .020" in length is a possibility.

That ring above the belt does give me pause though.

I'm in the same camp as Supercorndogs.

Mike

 

[Mike Casselton]

I have a Remington 7 Mag from the early 90s that does the same thing to new brass.
I don't worry about it, I just resize them back .002-.003 and fire away.

 

[wade2big]

That growth is pretty normal for a belted a mag for the reasons in post #2.

The shoulder on the brass in both of my 300WM barrels moved about that much also. I also took some of the Winchester brass I had for my first barrel to 15. It looks like it is still useable, but i don't shoot that much 300wm anymore and started with new brass on my new barrel.

Have the cases in the photo been sized? Its not the die rolling brass to the bottom is it? It comes out of the chamber looking like that correct?

Thinking about is I am not sure I would expect such a sharp edge if it was a false shoulder from firing it once. I had a small base die that would roll brass up like that on 6.5 Grendel cases.

Do you use regular dies and go or do you add the additional die with the collet to size all the way to the belt?

 

[supercorndogs]

Do you use regular dies and go or do you add the additional die with the collet to size all the way to the belt?

I have one of the Larry Willis collet dies, but I only ever had to use it once on the brass for my last barrel. I didn't even finish fireforming the new brass for the my new barrel. I picked up a 280 barrel and another bolt and shoot it a lot more. I wouldn't doubt that if a guy didn't try to hot rod it. He wouldn't ever need one.

 

[supercorndogs]

I have a Remington 7 Mag from the early 90s that does the same thing to new brass.
I don't worry about it, I just resize them back .002-.003 and fire away.

The 2 part cutting process mentioned by 918v makes sense. With the belt cutter being ever so slightly larger just a above the belt than the other chamber reamer.

 

[D̷e̷v̷i̷l̷D̷o̷c̷A̷Z̷]

Do you use regular dies and go or do you add the additional die with the collet to size all the way to the belt?

At this stage I’ve only shot factory ammo