Resizing question

[TrapperBR549]

I have a new rifle I am working up loads for to take on an elk hunt this fall. Rifle is a M70 extreme weather in 300 Win mag.
I bought 2 new boxes of Winchester ammo for breaking in the barrel and fire forming the brass. After fire forming I loaded and shot the brass twice more.
I was loading last night and bumped the shoulders back .003" but when I chambered it with the firing pin removed from the bolt there was significant resistance when closing the bolt.
I adjusted the die and sized again, bottom line I had to bump the shoulders .007" before the resistance went away.
I am using RCBS standard dies, Bonanza Coax press, 200 grain Sierra Gamekings, IMR-4831, Federal primers. Powder charges varied as I was trying different loads but none of them showed signs of pressure.
Is this normal or is there something else I should be looking at?

 

[JFrank]

Might be the base not the shoulder that needs attention.
Just a guess mind you.
J

 

[hogpatrol]

Two words, Winchester brass.

 

[TrapperBR549]

How should I address it? I have calipers, RCBS casemaster, and Bonanza measuring devices.

 

[JFrank]

How should I address it? I have calipers, RCBS casemaster, and Bonanza measuring devices.

A Sheridan gage with a cut away if they make that caliber would expose the area of concern.
Personally I measure the body before and after sizing at the .200 line and the case shoulder junction

 

[TrapperBR549]

A Sheridan gage with a cut away if they make that caliber would expose the area of concern.
Personally I measure the body before and after sizing at the .200 line and the case shoulder junction

What are you looking for when you take those measurements? By ".200 line" are you referring to just above the belt?

 

[TrapperBR549]

Two words, Winchester brass.

Ordering some Hornady brass next. Will see how that goes.

 

[JFrank]

What are you looking for when you take those measurements? By ".200 line" are you referring to just above the belt?

Whoops
I forgot all about that darn belt.
I’ll have to stand down

 

[243winxb]

I adjusted the die and sized again, bottom line I had to bump the shoulders .007" before the resistance went away.

The die sized lower towards the belt area? Should be ok for a hunting rifle.

 

[TrapperBR549]

The die sized lower towards the belt area? Should be ok for a hunting rifle.

I didn't check that, I just kept lowering the sizing die slightly until the bolt closed easily which happened when I had set the shoulder back .007" .

 

[alchemist]

Google "Larry Willis Technologies". I use his die for a 300 Weatherby and it works. It is expensive, approximately $120.

 

[hogpatrol]

What's your case overall length when you got the .007 reading versus the unsized reading after fire forming? Also, have you checked for a carbon ring?

 

[divingin]

Take a fired case and go over the entire thing with a Sharpie (or other marker.) Work it in and out of the chamber a few times (assuming you can close the bolt), and look for where the ink is worn off. That should indicate where the problem is.

I suspect the base (just above the belt) has enlarged and is dragging, but that's just a guess.

 

[TrapperBR549]

Google "Larry Willis Technologies". I use his die for a 300 Weatherby and it works. It is expensive, approximately $120.

I actually bought my comparator from him. Had heard some liked the die and some did not so it is good to hear it works well.

 

[TrapperBR549]

What's your case overall length when you got the .007 reading versus the unsized reading after fire forming? Also, have you checked for a carbon ring?

I did not measure before and after. I did trim the after sizing them. They weren't quite to the max length but the case mouths looked like crap so I hoped it would make them more consistent.
I will measure that next time though. What will that information be telling me?

I got a teslong a couple weeks ago so the carbon is gone, after much scrubbing.

 

[Murray Brook]

What you probably have is a die that doesn't match up well with your rifle chamber. Happens often with belted mags. You set the die to give you .002-.003 shoulder bump and good case life but the base does not get sized down far enough at the base.. If you screw down the die more to get the base sized you then increase shoulder bump and reduce case life. The Larry Willis die works great to size this area and is one option. Another would be if you had a 300 Weatherby sizing die you could try running your case all the way up the die till it touches the shell holder with no worry of bumping the shoulder as the Weatherby case is longer than the 300 Win case. If this works then you just run it in your 300 Win die to get the shoulder bump that you desire. Might work, and a 300 Weatherby die is much cheaper than the Willis die.

 

[piie]

What you probably have is a die that doesn't match up well with your rifle chamber. Happens often with belted mags. You set the die to give you .002-.003 shoulder bump and good case life but the base does not get sized down far enough at the base.. If you screw down the die more to get the base sized you then increase shoulder bump and reduce case life. The Larry Willis die works great to size this area and is one option. Another would be if you had a 300 Weatherby sizing die you could try running your case all the way up the die till it touches the shell holder with no worry of bumping the shoulder as the Weatherby case is longer than the 300 Win case. If this works then you just run it in your 300 Win die to get the shoulder bump that you desire. Might work, and a 300 Weatherby die is much cheaper than the Willis die.

Thanks for that idea!!!! I inherited a 300 wby die set and now I can use it on my 300WM if I run into the same issues as the OP. I have Norma brass with multiple firings on and so far I don't have this issue (touch wood).