Belted Magnum - Won't chamber

[Zzuffendoffer]

A number of you have mentioned LarryWillis..... I snagged one of these off ebay for 29.99 couple weeks ago!!! (sorry Larry)



I suspect these are just too far out of spec to salvage as I don't want to bend the handle on my press trying. I do plan on using that collet die going forward though. Its an extra step but I seem to have plenty of time.

Also, I'm pretty certain the shoulders are not the problem.... I put one of the shells on my lathe and cut it off 1/4" below the shoulder... It wouldn't chamber.
I will pick up that Hornady comparator though. Thanks for the link.

WinXb243, thanks for the detailed images. Am I reading that correctly? Belt Diameter .532 +.012 ? Does that mean max would be .544? All of my purchased brass fall below that... but won't chamber unless i turn them a down couple thousandths.

 

[AlNyhus]

257 Chamber slop-Tolerances .011" maximum. This is the difference between .224" chamber headspace max & .213" cartridge min.


Head to shoulder (not datun) 2.1131" chamber maximum & 2.1047" cartridge minimum. A difference of .0084" (slop) An estimate because there is no SAAMI datum diameter.

So, in a sloppy chamber, it may be possible for the area in front of the belt to become unsupported & bulge with maximun pressures? This is when setting the die to size with a .002" shoulder bump. Head clearance of .002"

The unsuppored cartridge area may be as much as .008" in a sloppy factory chamber?

Right or wrong?? This gave me something to do while in lock,down.

Well.....yes and no.

Honestly, whatever clearance difference there is from bolt face-to- chamber 'datum' and the cooresponding bolt face-to-case 'datum' (when the case is held in the bolt face) is just a clearance issue to be dealt with.....the same as any other non-belted case.

How it's dealt with is what makes all the difference, both in case life, ease of chambering, etc. Some trust in luck.

In the 257 Wby I load for, the 25 new Weatherby/Norma cases I started with have each been loaded 12 times with no issues. I have one 'fouler' case that has well over 20 firings on it.

You only get once chance to make a really good case when f-forming. That goes double for belted magnums and triple for the Wby chambers.

Just my experience, FWIW. -Al

 

[Uncle Ed]

Below the belt diameter manufacturing tolerance is .532-.005 or .532 to .527. The image 243winxb posted is cartridge and chamber headspace tolerances. Your once fired cases were loaded so hot the belt expanded in diameter.

I would check to see how loose the primer pockets are before wasting any more time on these second hand cases. I would toss the cases and buy new cases and never buy anything used off the internet unless you know where they live.

Below shows base expansion on a standard non-belted case, "BUT" explains why the belts expanded larger in diameter on your cases. What did the primers look like and did the cases have ejector marks?

Note to all reading this post, the OP could not get the cases to chamber until he reduced the belt diameter. Meaning this is not a headspace or fire forming problem, his cases have a fat ass or over size belt diameter. The base of the case stretched and expanded in diameter beyond its elastic limits.

 

[243winxb]

Am I reading thatcorrectly? Belt Diameter .532 +.012 ?

(.534 + .012")
This is the chambers belt diameter. The area where brass may become unsupported.

What did you turn off to make a round chamber? The area in front of the belt? This is the normal problem area .

 

[Uncle Ed]

This is the chambers belt diameter. The area where brass may become unsupported.

What did you turn off to make a round chamber? The area in front of the belt? This is the normal problem area .

243winxb what you posted is the rim diameter tolerances and not the belt manufacturing tolerances. Look at the SAAMI image I posted, it shows the belt diameter tolerances and are not the same as the rim diameter.

 

[243winxb]

I sold my 300 & 7 mags. Good luck.

 

[Zzuffendoffer]

Here is a picture of one of those cases before and after I turned...
You can see the roll of brass just ahead of the belt.
Diameter of the belt before turning was .541




In the next image, the Red arrow points to where I trimmed the case.... First and tried to chamber with no luck.
The green arrow in the second shows where I turned the belt down just a tad. Once I did that, it would chamber fine.
Diameter after turning was .534



I guess this is more or less a knowledge gaining experience. I don't plan on using this stuff. Just trying to understand whats going on.

 

[RegionRat]

Those are toast. The dimensions there are what that collet die is supposed to help manage because conventional dies will not, but your cases are so bulged that they were beyond salvage. Really makes you wonder what the previous owner did to them?

 

[Dusty Stevens]

I have belted magnums that never hit the shoulder so bumping them back .001 every time is useless. I only have to size the base above the belt and keep going. Belted magnums are just a bad design and i avoid them pretty hard reloading wise now.

 

[AlNyhus]

I have belted magnums that never hit the shoulder so bumping them back .001 every time is useless. I only have to size the base above the belt and keep going.

On new belted magnum cases, annealing the shoulder and a light bit of lube on the case (before the first firing on virgin brass) lets the shoulder come forward and fill the chamber.

Good shootin'. -Al