.50 cal. minie bullet question....

[Jeff B.]

I'm looking to build a black powder cannon out of a M2 .50 BMG barrel which has a .510" bore diameter. I was looking at using a .50 cal. minie bullet as a projectile.

Lee Precision has a .50 cal. minie mould that produces bullets that are advertised at being .500" diameter. I have (2) questions:

(1) Would a .500"  minie bullet expand out to .510" with out much problem? Not having any experience with them, I really don't know.

and

(2) The M2 .50 BMG barrel has a twist rate of 1-15". I realize that this rate of twist is probably too fast for the minie bullet, however, could there be problems with the bullets flying apart from too much rotational velocity?

I realize this is probably going to be a trial and error situation but I wanted to ask first just to see if I was heading the right direction.

Otherwise, I guess I'll have to shell out some extra money for one of those custom .50 BMG cast bullet moulds.

Thanks.

[simonkenton]

An interesting project! I am afraid to ask, where you got the barrel. As I understand it, if the twist is too great for the projectile, the projectile tends to "skip" the rifling as it goes down the barrel. I can't imagine that it would spin so fast that it would be pulled apart.
So you are going to thread the breech and screw in a breechplug? How are you going to ignite your cannon? Keep us posted.

[Jeff B.]

Thanks for the reply.

Barrels are readily available for a bargain basement price of about $60 USD here in Kanuckistan (Canada).

I plan on making a removable breech block using 4130 or 4140 round stock steel (if available). I'm going to drill then have the breech block threaded to match the existing threads threads on the barrel. I plan on having at least .500"-.750" steel wall after the threads. I'll put a bolt handle on the block to make it easier to remove/tighten. It should be plenty strong enough to handle the relatively small amount of black powder that the .50 BMG chamber could hold (close to 375 grains by my estimation).

I'll drill a hole through the barrel threads and breech block so that I can use safety fuse for an ignition source.

I intend to purchase the barrel this week.

[simonkenton]

You are a wild man. 375 grains of powder! How long is that barrel? On our muzzle loaders, with a 32 inch barrel, you are only able to burn about 120 grains of powder. I think if you go up into the 150+ category, most of the powder won't burn, and it will create a lot of fouling. Keep us updated please.

[savageT]

I don't think tht twist rate will work.....The fastest twist I am aware of is 1:20", with 1:28" being used for most 50 cal. in-line sabot shooters???  Perhaps the heavy conicals (500 grain plus) might get you somewhere.

Jim