Case issues

[gedsar]

Hi boys,
I have a M70 featherweight in 243WSSM. I have been reloading for it since new. The last batch I done with the same load as always (46gns AR2209, 210p, 85 HPBT sierra) has been putting a crater around the pin mark in the primers (like a mini mountain range right around the pin dent), never did it before. So I backed it off to 45gns and still the same. Then today I fired a factory win 100gn load through it and it cracked the case from approx half neck through shoulder to about 40thou into case wall running along it axis. The primer had cratering but not as big as the handloads. I heard some of the M70 300WSM's had crook chambers when new, could I have one?
Rifle was brought new and has only ticked over 100rds.

Any ideas on what is causing these issues?.


Thanks Paul

 

[davewilson]

your cratering is probably a clearance issue between the firing pin and hole that it rides in. when there's too much clearance, cratering shows up on the primer. different primers show different amounts of cratering because of the thickness and hardness of the metal used in the primer cup. a good smith should be able to tell you what the problem is. if you don't have extractor marks on the brass you don't have too much pressure.