The small base die didn't cause the case head seperation. Bumping the shoulder too much did. Thats not what a small base die is for. MattI used a standard RCBS full length die for my Remington 760 pump and also never had a problem. And Barlow raises a good point about chamber diameter and even a standard die might be a "small base die". Meaning how much the die reduces the case diameter.
I had someone I hunted with that also had a Remington 760 pump, "BUT" someone told him he needed a small base die for reloading it and he was having case head separations. This was in the early 1970s and both of us were following the RCBS dies instructions. Meaning with the die making hard contact with the shell holder. And I never had a case head seperation in my 760 pump. I'm not sure if it was the amount of shoulder bump or the dies diameter that caused my hunting friends case head separations.
So again chambers and dies vary in size, and all you need to do is measure a fired case and a resized case. To know if you are reducing the case diameter enough for the type rifle you have.
Example below for the .223 and 5.56 AR15 chambers, the base diameter of the AR15 chamber is .002 larger. And in a semi-auto the resized case should be .003 to .005 smaller diameter than its fired diameter. This allows the case to spring back from the chamber walls and extract reliably. Meaning in a bolt action rifle with a smaller diameter chamber the case has more time to cool and spring back from the chamber walls. (as long as your not the Flash or Superman and faster than a speeding bullet)
NOTE, no magic feeler gauges or shell holder were used in the making of the posting.
That Greek case doesn't come in a 760 or any other Remington. I have had lots of 760's and the chambers were like the 700. That thinning of .009 didn't cause the separation on the 760. Bumping too much there after did. MattA skinny case fired in a fat chamber has to stretch to outward contact the chamber walls and stretch to meet the bolt face. Meaning the case can stretch in two directions at once. And the 760 pump has a larger diameter chamber just like a semi-auto than most bolt actions have.
And if you use a small base die on the HXP case below it will cause a case head separation even with the correct amount of shoulder bump. And both cases below were fired in the same chamber.
The factory loaded case below stretched and thinned .009 on the first firing and the rifle was below the SAAMI NO-GO gauge. But the military chamber it was fired in was very large in diameter. So never say never, it is chamber size vs die size.
I was just thinking the same thing before I read your post
A skinny case fired in a fat chamber has to stretch to outward contact the chamber walls and stretch to meet the bolt face. Meaning the case can stretch in two directions at once. And the 760 pump has a larger diameter chamber just like a semi-auto than most bolt actions have.
And if you use a small base die on the HXP case below it will cause a case head separation even with the correct amount of shoulder bump. And both cases below were fired in the same chamber.
The factory loaded case below stretched and thinned .009 on the first firing and the rifle was below the SAAMI NO-GO gauge. But the military chamber it was fired in was very large in diameter. So never say never, it is chamber size vs die size.
This is very good,however the cases shown are .303 British,the HXP are smaller at the base than the Privi Partisan,which most likely made to the correct dimensions.What you are saying is correct in that some chambers have length as well as diameter measurements that need correcting at the same time.A skinny case fired in a fat chamber has to stretch to outward contact the chamber walls and stretch to meet the bolt face. Meaning the case can stretch in two directions at once. And the 760 pump has a larger diameter chamber just like a semi-auto than most bolt actions have.
And if you use a small base die on the HXP case below it will cause a case head separation even with the correct amount of shoulder bump. And both cases below were fired in the same chamber.
The factory loaded case below stretched and thinned .009 on the first firing and the rifle was below the SAAMI NO-GO gauge. But the military chamber it was fired in was very large in diameter. So never say never, it is chamber size vs die size.
Thats funny ,never heard that before. I'm a proud Marine for sure but I always thought if I had to do it over I would go Air Force......lol
Get the small base die, it will likely solve your problem. One possible cause of your problem is a chamber that is smaller than your current dies can accommodate.
