I have been using SB, RCBS .300 Win. Mag. dies for years, however, when I loaded the last batch of bullets (180-grain Nosler Partitions), it seemed like the bullets were seating awfully loose, so I pinched one and pushed. Low and behold, it slid back into the case.

Now, this was the first time I ever lubed the inside of the case mouth before before sizing. Could this cause loose necks?

Is this a die problem or a case problem?

I've had this happen, it is either operator error... the die needed to be screwed down just a hair more...

I've had this happen to just a few cases out of a batch of say 20 also... on the one's that happened with, the neck thickness was just a hair less than the others... so tightening down the sizing die just a little more el9minated the problem...

When I have Lee Dies in that caliber, I use the neck sizer die to do that instead of the full length die... I also have broken off the decapping pin on purpose so I can do this, when the problem arises..

It is an extra step, but for safety's sake, I deprime all brass using a Universal DeCapping Die...

If I were experiencing what you are:

I would polish my expander down about .001"

Forget the inside neck lube if possible.

Make sure as you remove the case from the sizing die that you get a feeling that your expander is doing something. roger

Old age is a high price to pay for maturity!!! Some never pay and some pay and never reap the reward. Wisdom comes with age! Sometimes age comes alone..

I believe you have a case problem. I have run across this before, where after resizing, cases expanded back acting as if no sizing had occurred.

leon - after you've reloaded the cases over 50 times and scotch taped the neck cracks up, you just gotta expect some freeplay

I've had the issue with work hardened brass. Have you tried annealing them?

problem is the brass is work heardened as mentioned. anneal it and problem will go away.