ihmsa forums

I am having my XP100 in 7br rebarreled. I am playing with the new barrel to see if my loaded cast rounds will chamber and they will not. The new barrel has a .310 neck. If I use the M Die to flare the mouth, the dies will only iron out the flare to .311 and the rounds will not chamber completely. If I don't flare with the M Die, I scrape lead. Any suggestions?

Turn the necks?

I am pretty sure the necks are ok. Jacketed loads chamber fine. It is just ironing out the flair from the m die. Another forum suggested that I adjust the sizer die to kiss the flair. I have a full length die and a neck sizer die, so it might work out well. I will try it tomorrow morning.

This is the way I do it, But the guns I shoot with cast bullets do not have tight necks. what I do is use the M die to flair, then adjust the seating die to perform a slight crimp after seating bullet. seems to work on my guns and cast bullets.

I did notice that you flair the mouth more than I do. I adjust my M dies to just have a slight flair enough to allow the cast bullet to enter case and not shave lead.

Crimp the case mouth ever so slightly. All your brass has to be the same length, or you will have varying crimp. Use an empty, sized piece of brass, flare the neck, then run into your seat die a little at a time , screwing the die down a little each time until it just takes the taper out. Lock your seat die down. It’s really better to crimp in a separate step, but it is more work.
At least that was the way I did my 300BO
Melvin