I just got an order in of new RMR 9MM 124 GR FMJ bullets and I am having issues with the bullets not staying seated in the case. I noticed it yesterday when I was getting ready to go to the range and I was able to push the bullet into the case by hand. I re-measured the 200 rounds that I just reload and about 25% of them I could push the bullet into the case further by hand. I have tried changing OAL, re-adjusting the expander die, increasing the crimp on my Hornady bullet seating die and I just cannot get them to stay in place. All of the brass is under the max length and it is all range pickup brass so not just one manufacturer. I am thinking about ordering a LEE factory crimp die but has anyone else had any issues with RMR FMJ bullets?
Thanks!

Have you measured the bullets? Maybe they're undersize

I don't have a micrometer at home but the dial calipers show the bullet diameter at .355 at the base.

I have loaded many of those.  Never had that issue.  I use just enough crimp to iron out the bell.  You sure your resize die is set right?

I can't say for sure what your problem is, but I can tell you that won't fix it.

Size a case and then measure it at the mouth. Then expand it and measure again. Post the numbers.

I will double check the resize die.

I reset the resize die and it fixed the issue. Not sure what happened but now I get to pull and resize everything...

Glad we could help.

Welcome to ARFCOM.

The guys in this reloading forum have a wealth of knowledge, and there is some good info in the tacked threads here.

Wait, you joined in 2009 and just made your first post?

You guys are great! Maybe I will try to post more than once in 9 years.

Nothing wrong with just hanging out and learning. Lots of good problem solvers here.