Question about cryrogenic barrel treatment.

[Longcruise]

The same problem occurs with maxi-ball or minnie and "Magnum" loads. The projectile is forced forward so fast by the heavey charge, it can't get rotation from the barrel properly. It will have Feet Per Second^,,and it will have Foot Pounds of Energey^,butt,,,,

Hmm.  I've shot some very heavy conical charges in .50, .54 and .58, up to 120 grains of ff, and never had this happen.

On some days, with high humidity and shooting with tc 1000+ I have been able to shoot dozens of prb shots without any loss of accuracy or perceivable change in impact point.  When the humididty goes down to a more normal for my area of 15 to 30 percent, the fouling hardens up no matter what the lube and must be wiped after every shot.  Under those conditions, the ability to get the ball down the bore becomes impossible before accuracy goes to pot

[Winter Hawk]

May I jump in here?  When I got my GPR I took a "green scrubby" and cut it into about 1" x 1 1/2" patches.  I wrapped one these around a bore brush on a cleaning rod, soaked it  with cutting oil and commenced scrubbing the bore.  I replaced the green scrubby patch after every 10 - 15 in and out strokes.  I kept this up for 100+ strokes in and out.  I then scrubbed out the bore with hot water & dish soap, lots of patches.  Since then I have not used any petroleum based lubricants.  I use olive oil for patch lube.  After I clean the bore I run down a patch with olive oil cooking spray to seal it.  

I haven't had any problems with fouling, though I run a dry patch down after every shot between shots, just because.  

The other thing I did was to cone the muzzle.  This allows me to start the ball with my thumb, not a short starter.  It has not hurt accuracy at all.  I am getting 1 1/2" groups at 50 yards using the primitive rear sight which came with the GPR.  However, I filed the "buckhorn" doodads off so it is flat topped, and cleaned up the notch with a hacksaw blade so it is a square groove.

This is a .54 flintlock and I am using 80 gr. of Goex fffg, priming from the horn.  On a .50 I advise dropping down to 60 gr. or maybe even less, then work up in 5 gr. increments as lostid suggests.  Usually you will find the best load in grains around 1 1/2 X the caliber.  In a .50 that would be 75 grains.

Good luck.  A lot of the fun with these things is the playing around (though over two years and still having poor accuracy would get to be discouraging, I suppose).

-WH-