243wssm big problem help!!!!!!!

[mt boy]

I have a winchester m70 super shadow in 243 wssm gun is almost new.It has between 65 to 70 factory rounds put threw it.At the range today after 3or 4 rounds it started spliting the necks on the cases.Was useing 2 different factory winchester rounds and it was spliting thecasesabout 2 out of 4 shots.Is this my rifle or ammo.If my rifle what would the problem be.

[stalkingbear]

Didn't I see this post in other section? Is the case necks visably larger or "blown out"? Take dial caliper to them and measure them and let us know what they measure.

[bronko22000]

Do what stalkingbear suggest. Also, how many times has this brass been loaded? Could be you have to anneal the case mouths.

[sns21]

Had a lot of trouble with a Browning .243ssm, had to start reloading my own ammo. I'd call Wichester though, if the necks are splitting on factory ammo, head space may be wrong.