BP cartridge question

[RyanJames170]

So I’ve heard black powder is better at bumping up bullets to grove diameter then smoakless powder is.. my question is would BP bump a .308 jacketed bullet into a .303 bore if it was a open base heavy bullet. I am thinking about messing with 303 BP and would like to use 200gr bullets and I can not find jacketed 200gr 303 bullets

The reason I’m thinking on using jacketed bullets is from watching others do this I suspect it makes the pressure go higher and thus burn cleaner.

[Woodtroll]

My short answer/opinion is that it won't work well, if at all. The "bumping up" with black powder requires that the bullet be pretty soft lead - there's whole pages of discussions about what lead alloy/hardness works best for a particular bullet shape and application. Harder lead alloys bump up little or not at all under a lighter charge. I don't believe a jacketed bullet, being harder, will ever bump up enough to seal a 0.311/0.312" bore.

As always, you can't believe everything you read, and I could be wrong. It can't hurt to try (at least, it won't be dangerous, anyway ;-)). Do your .303 dies size down small enough to hold a .308 bullet?

[HWooldridge]

I agree…seriously doubt that you’ll see any “bump” on a jacketed bullet - in any caliber.

[ascast]

Try it. Be very careful if using soft point open base. Check bore between shots. There is an old story about some surplus ammo, Swiss ( ? ) or something that guys filed a flat spot nose on to for hunting. In practice, the lead cores shot out and left the jacket stuck in the barrel. Next shot is a BOOM. Lead shooters use pistol powders also to bump up bullets. I think you will be safe using black. Be careful.

[Rockindaddy]

Better look for British surplus ammo that has dead primers. I have a lot of 7.65 Argentine dud ammo that I pull down and use the powder and the bullet.
the 308 jacketed bullets will not bump up to ride the 303 bore. Send a private message with your address. I will send you some Argentine bullets that are .312 for you to try out.