Having to bump shoulder an excessive amount?

[Eric Leonard]

if he pushed the shoulder back .013 the case is still gonna stretch back to fill the chamber no mater where it headspaces ,,I would think,,

I am usually wrong though,,

 

[Never Forget]

The OP is talking about pushing/bumping the shoulder back .013, and his belted case headspaces on the belt and not the shoulder.
I think what happened was he reduced the case diameter more by pushing the case further into the die.

I would measure a new case just above the belt and then a fired case and see how much it expanded. I would then blacken this area with a black felt tip marker on the fired case and see if the case is rubbing in this area and pushing the base of the case off center.

I will give that a look next time I'm out with it, if the weather man is correct then it wont be this weekend.

 

[John Russell]

If your case wall thickness was not a even thickness just above the belt the egg shaped case may have been pushing the case out of alignment with the axis of the bore. Meaning when you size all the way down the body of the case it was better aligned with the bore.

If you want the case to headspace on the shoulder then you may want to try the Larry Willis collet die. You might have warped banana shaped cases. Normally a full length resized case is .003 to .005 smaller in diameter than the chamber.

Belted Magnum Collet Resizing Die
"Finally a resizing die that works on belted magnum cases."

http://www.larrywillis.com/

One of the biggest wastes of money in handloading.

 

[XTR]

if he pushed the shoulder back .013 the case is still gonna stretch back to fill the chamber no mater where it headspaces ,,I would think,,

I am usually wrong though,,

I would agree that it will stretch to fill the chamber, but I'm not sure at what point on the case the belted magnum is stretching. Non belted cases stretch at the web because the firing pin strike drives them forward, then the case expands in the chamber and the case head stretches back to the bolt face. A belted magnum isn't doing that.

 

[RonAKA]

I would agree that it will stretch to fill the chamber, but I'm not sure at what point on the case the belted magnum is stretching. Non belted cases stretch at the web because the firing pin strike drives them forward, then the case expands in the chamber and the case head stretches back to the bolt face. A belted magnum isn't doing that.

The failures I have seen in belted magnums are about 1/4 to 3/8" above the belt. They get thinner from the inside until the crack shows all around on the outside. Those I know who have the issue check for bad cases by using a hooked wire to scratch up and down the inside of the case to check for that thin spot developing.

I agree that if you keep pushing the shoulder back 0.013" extra it is only a matter of time until the case head separates.

 

[SheepDog]

The failures I have seen in belted magnums are about 1/4 to 3/8" above the belt. They get thinner from the inside until the crack shows all around on the outside. Those I know who have the issue check for bad cases by using a hooked wire to scratch up and down the inside of the case to check for that thin spot developing.

I agree that if you keep pushing the shoulder back 0.013" extra it is only a matter of time until the case head separates.

Yes! the case is pushed forward to the belt and then pushes the rest of the case forward, stretching the case just above the belt. This is common with all belted magnums that are not sized to headspace on the shoulder rather than the belt. The only belted magnums that don't recommend headspacing on the shoulder are the original H&H magnums.

 

[Dubbo]

I had a Rem 700 BDL 7mm rem mag that expanded the case shoulder out 0.019" and also shot good with new brass. When I full length resized them I pushed the shoulder back roughly 0.0015" and my groups opened up with the same load. I ended up tweaking that load with once fired and resized cases but if I remember correctly I tried a different powder (was slightly faster) and got slightly better groups over the new brass. Maybe with the expanded case you get more volume, different pressures hard to say? For that reason and several other experiences I have had belted magnums have always seemed finicky for me, maybe its just me...

 

[mikecr]

You should always load develop, and with fully fire formed stable brass.
Otherwise, it's classic tail chasing..