Thread: Fixing Belted Magnum Bulge - DIY Method

Hello Gents,

I recently purchased a 7mm Rem Mag Browning X-Bolt and also bought some once fired Norma brass off Trademe.
I found that the cases all had a bad bulge right in front of the belt. SAAMI spec is 13.02mm. these measure 13.25-13.30.
My FLS die could not deal with this and just shaved brass off and pushed it up against the belt. Not being able to get hold of one of the collet body dies (and being impatient) I decided to try squeezing the bulge out using a 13mm ER32 collet held in a collet block in my mill vice. Long story short, it works! It takes quite a bit of force, and you have to size it, the rotate it a small amount and size again to remove the lines from the collet, but after that I am able to run it through my FLS die perfectly and it chambers in my rifle.
Its not a fast method, but if you have ER collets and no collet body die, you can salvage oversized brass.

Is that bulge not impending case-head separation?

Originally Posted by StrikerNZ

Is that bulge not impending case-head separation?

No but if you size with the die down hard on the shell holder trying to remove the bulge that can be a cause of head sep. The bulge needs to be removed as a separate step to prevent setting the shoulder back. The belt serves no useful purpose in many belted cases.

An alternative I thought about was getting a second hand 7 rm or 300 wing mag full length die and cutting off the top ( removing all the neck part from it) and turning down with a lathe bottom maybe 1 or 2 mm past the belt location . And you are just adjusting it till it resizes that bulge with out touching the neck. The neck can be done separately after with a normal die.

Originally Posted by StrikerNZ

Is that bulge not impending case-head separation?

I sectioned one of the cases to check this out and there is no sign of thinning. They have only been fired once.

Originally Posted by Friwi

An alternative I thought about was getting a second hand 7 rm or 300 wing mag full length die and cutting off the top ( removing all the neck part from it) and turning down with a lathe bottom maybe 1 or 2 mm past the belt location . And you are just adjusting it till it resizes that bulge with out touching the neck. The neck can be done separately after with a normal die.

This is what I have done. I ended up with an RCBS and Lyman FLS die, so I bored out the neck and shoulder section of the Lyman, plus shortened the base a little. Now I can size hard up against the belt and the shoulders are not pushed back at all. This is handled by the RCBS die, which has been shimmed to provide about 0.02" of shoulder bump from what my rifle will close on. Lots of steps.

Originally Posted by grandpamac

No but if you size with the die down hard on the shell holder trying to remove the bulge that can be a cause of head sep. The bulge needs to be removed as a separate step to prevent setting the shoulder back. The belt serves no useful purpose in many belted cases.

Yep, originally I think it was there to set the headspacing on the old straight walled big bore cartridges. Nowadays on bottleneck cases it's a hangover that creates more problems than benefits, as most still set the cases up to headspace off the shoulder. I never thought about setting up the ER collets to squeeze the bulge down, nifty. Probably never have to do it now haha. I've only ever used the collets to nick old crimped in berdan primers out...