I have been trying to seat flat base matchking in .222Rem cases that have been sized with a LEE collet die.

It seems like the collet reduced the neck too much and now the bullets won't fit in.

Most of them are ripping or curling over at the base of the bullet.

Do I have to fin the right pressure with the LEE collet die in order to be able to seat bullets?

At first I thought I had the seater down too far and was forcing a roll crimp onto it, but I came back a full turn and a half again so that isn't the problem.

I think I might have to fiddle with the collet till I find a setting that gives me the correct tension. But that's a pain, or is it likely to be something else?

I don't think there's any fiddling with the collet die that will work. The size of the mandrel determines how much the neck is sized. You may want to order a slightly larger mandrel from Lee.

Did you chamfer the case mouths?

Yes, I did champher the case mouths, and the bullets are .224cal Sierra Matchkings...



I need to take some measurements of the mandrel.



The strange thing is that the first time I passed the bullets through this die, primed, charged with powder...placed a bullet on top and it fell in.

Case mouth too big.



So I readjust the die to I get that little bump at the end of the stroke a little more positive and try again. Case mouth too small.

You can actually see the bulge in the neck once the bullet has gone in, and the other thing which I forgot to mention is that they are also very very askew, visibly off out off center.



Hence thinking I need to fiddle and find a setting that will give me correct tension, but that doesn't sound very practical, nor will it neccessarily resolve the concentricity issue.