Thread: Substituting projectiles

People are making this sound really complicated. Its not. Pull the bullets, set up your die for neck sizing, take the decapping pin out or the expander completely) neck size them all. Take an average of the weight of the powder and then put it all back again, and then seat the new bullets.

Its very simple. And really, none of the things people are talking about above are going to happen. You'r not going to be over pressure. You're cases are not going to grow at all (you're neck sizing)
It's going to be fine.

Lee f/l dies are not neck sizing dies if you remove the rod they will outside diameter the neck in a very aggressive manner . This is to accommodate brass of all thicknesses , the final neck sizing is done by the expander ball as it is drawn back through the neck . If the OP were using a bushing die then things may be different.
The cases may grow if the die sizes the body without engaging the case shoulder , not will , may . So just in case , how difficult is it to check a case or two will chamber .
The ideal would be to use a Lee Collet neck sizing die with the decapping rod lifted up out of the way . The rod itself works as a mandrel to help keep the neck concentric.
Personally, I'd air on the side of caution . The propellant is unknown and changing bullets even to one of the same weight may change the internal pressures, especially if the bullet is longer then seated to the same c.o.l , as you may be reducing case capacity . I strongly suspect mil'spec fmj's will be considerably shorter than modern hunting bullets, with their boat tail and polymer tips .
Anyway , it's entirely up to the OP how he proceeds and whose advice he takes .
I'm done on the subject.