Compressed Load/Airspace?

[Steve Swartz]

Guys:

I have an underhammer "Dueling Pistol" with a "patent chamber" (narrow chamber at end of barrel for powder; bullet too fat to enter).

After much finagling looks like the volume is ~0.06" or so cubic inches; probably a milliliter (makes sense- pedersoli gun!).

And it looks like a milliliter holds right around 15 gr of FFFg.

I crunched this several different ways with data from different websites and applied my trusty CRC manual . . . and it all came out fairly consistent.

O.K., so given that it takes around 15 gr of powder to fill my chamber . . .

. . . would I need a load of at least 15 gr for optimum consistency?

The mfgr recommends 12 gr load- but this is leaving an airspace over the powder and does not allow the ball to compress the load firmly.

Bad mojo?

Steve in North Texas

 

[paulvallandigham]

YOu can use a smaller charge( the 12 grains recommended, but you should also then use a filler like corn meal, cream of wheat, PufLon, tobacco, or even dead leaves ground up between your palms, to fill that small airspace and give the ball something to seat against. At those small charges you are not going to blow the barrel up with that small air space, but its not going to give you consistent accurary either. I would simply load 15 grains, or try FFg as it might take more space, and fill up that chamber with only 12 grains.

Many of the pistol shooters who shoot for competition use a spacer or washer in the chamber of each cylinder in a revolver, to restrict the amount of powder that the chamber will hold, and give a place against which the ball is seated, all for consistency. It works. This kind of " powder " chamber " is just a fixed version of the same idea. You didn't give a caliber for the gun, but in a .36, the 15 grain load should be more than enough. I would recommend trying FFg powder, as you are burning such a small amount, there should be no problem burning the powder in the barrel with that volume of powder.

 

[Dphar]

The original 63 Springfield rifled musket was proved with a projectile spaced 2" off the powder. The proof load was 200 grains.
The Sharps percussion carbines and rifles all have 1/2" or more of airspace due to the design of the breechblock.
Having a little airspace is far different than having an obstruction such as a short started ball farther up the barrel.

Dan