30-338 case forming question

[DougH9]

I just got a new 30-338 Mag. barrel put on my reciever, and am in the process of making up loads. I want to use shortened 300 Win. cases, so that I can run a longer neck than I get with 7 Mag or 338 Mag. cases. I made up a batch, and they chambered fine until I seated a bullet. With a bullet seated the neck is too thick the last third of it's legnth, where I guess the 300 Win. shoulder was.

So my question is; Do I need to get an inside neck reamer, or an outside neck turner, or both?

Any help appreciated.

 

[Bart B]

I misread your post.

I'd turn case necks to .012-in. thick then seat bullets and try them. If that doesn't work, then....

Best take the barreled action to a competant 'smith and have him check the chamber, or ask the person who chambered it what reamer he used. Not enough info posted for me to offer any other suggestions.

 

[DougH9]

Bart, the cases (338's necked down)come out of the gun at .339".

Only part of the brass (300 Win. shortened)is too thick; the rear halve is thick, the front halve is fine. As the case comes out of the sizing die, the OD of the neck is the same (the bulge is on the inside at this point). So I think that outside turning will not accomplish anything here, unless I could do it with a bullet seated (then the bulge is on the outside)

 

[Bart B]

Try sizing the cases over a .311 or .323 caliber expander ball to open the necks up a bit oversize, then resize them in your die. I've done this a few times making .30-.338 long neck (or .30-.338 Keele) cases when the .300 Win. Mag shoulder-neck junction left a small groove in the neck and things worked out very well.

Outside neck turning typically uses a mandrel in the tool that's a snug fit in the tool to keep the cutter making neck wall thickness very uniform. This may also push the groove out and solve the problem, but try it on one test case to find out.

 

[DougH9]

Thank you Bart. I take it that by necking it up, then down again it might "iron out" the thick part. I will scrounge around and see if I can come up with something. But, what about getting an inside reamer and doing it when the thick part is inside the neck?

BTW-If you are Bart Bobbit, who wrote the article on twist rates for 30 cal. SMK's (I found it on a search), it was a big help for me when after buying my 12 twist barrel I had second thoughts. I can't wait to shoot this thing...the bedding is curing right now!