Ladies and Gentleman,

I just purchased a new Dillion 550b and started reloading my 40 S&W. I have loaded about a thousand rounds and have developed a problem.

Everything was good until I just bought a new batch of bullets to reload. Now I am getting case deformation when seating the bullet at the end of the bullet area on the brass. It looks like the brass in being pushed down to much during the seating crimping process.

I backed off the crimp seating RCBS die but it seems to still be happening.

Any comments?

Greg

Do you mean that you can see a bulge where the bottom of the bullet is in the case? You may want to measure the diameter of the new bullets. They may be oversize.

If you mean that the case mouth is being pushed down, you have to bell the case more before you seat the bullets. You may also want to check to see if the bullet will stand on the belled case to see if there is enough bell present.

Problems with the case mouth could also be from oversized bullets.

Not at the mouth but at the bottom of the bullet after it is seated.

Check your overall length. Even if your new batch of bullets is of the same weight, the bullet fit to the nose punch may be causing you to seat the bullets deeper. That would both raise pressures and cause the bulge you describe if they are being seated into the internal taper of the case.

I went back and reset the seating die again and it is working now. I believe that the bullets are of different length.

Thanks

I believe 40 S&W headspace on the mouth of the case, if so be careful.