07-26-2020, 12:42 PM
If I understand correctly your rifle has a 6PPC chamber and you are sizing 6.5 Grendel brass down to 6 PPC?
If the loads are in fact over pressure primer change will not matter as the primer pockets will be trash anyways.
While the CCI 400 does have a thinner cup vs a 450 over pressure is over pressure.
Things to check for..... 6PPC used for utmost accuracy , reamer's/chambers most times are designed with small neck requiring neck to be turned for consistent neck wall thickness and dia.
If your rifle was chambered with such a reamer and you are not neck turning your brass you do not have enough neck clearance. This will drive chamber pressure up as the case cannot expand to release bullet.
Try to drop a bullet into a fired case, it should drop in freely , if it will not this is propably your problem.
Also anytime you neck up or down a case it is easier to form a donut (build up of brass)at base of neck and will cause same pressure increase.
A carbon ring in throat can also cause pressure increase
A bore scope will be needed to check this out.
I would switch to 450's as they have a thicker cup and withstand pressure better . Although being a hotter primer they will increase pressure/velocity so back off charge weight .
The thing with pierced primers is the damage they do to the Bolt face/firing pin.
Everytime you pierce a primer the hot gas act same as acetylene torch cutting metal. This of course is bad as it weakens the Bolt face.
Inspect your firing pin as well, gas cutting may have made a sharp spot (or could be from factory) this will pierce primers as well, if so smooth up with fine sand paper.
If the loads are in fact over pressure primer change will not matter as the primer pockets will be trash anyways.
While the CCI 400 does have a thinner cup vs a 450 over pressure is over pressure.
Things to check for..... 6PPC used for utmost accuracy , reamer's/chambers most times are designed with small neck requiring neck to be turned for consistent neck wall thickness and dia.
If your rifle was chambered with such a reamer and you are not neck turning your brass you do not have enough neck clearance. This will drive chamber pressure up as the case cannot expand to release bullet.
Try to drop a bullet into a fired case, it should drop in freely , if it will not this is propably your problem.
Also anytime you neck up or down a case it is easier to form a donut (build up of brass)at base of neck and will cause same pressure increase.
A carbon ring in throat can also cause pressure increase
A bore scope will be needed to check this out.
I would switch to 450's as they have a thicker cup and withstand pressure better . Although being a hotter primer they will increase pressure/velocity so back off charge weight .
The thing with pierced primers is the damage they do to the Bolt face/firing pin.
Everytime you pierce a primer the hot gas act same as acetylene torch cutting metal. This of course is bad as it weakens the Bolt face.
Inspect your firing pin as well, gas cutting may have made a sharp spot (or could be from factory) this will pierce primers as well, if so smooth up with fine sand paper.