GM .62 Maximum Loads

[Good Cheer]

Does anyone have published maximum load data for the Green Mountain .62 barrels?

[HARRYMPOPE]

smooth bore?

[Good Cheer]

One smooth, one rifled. Hoping someone has maximum load data.

[Boerrancher]

For PRB I always considered 2x the ball dia to me the max charge on a rifle, I don't have any experience with a smoothie, and depending on your barrel length a good portion of it may end up being blown out on the ground in front of you. If you want to find your max load, buy a cheap roll of christmas wrapping paper and roll it out white side up on the ground in front of you, and start with 60 grains of powder, and slowly increase it with each shot. When you start finding powder residue in large quantities on the paper in front of you, the load before that is your max load. Any powder blown out on the paper is just wasted and does not aid in propelling the ball out the barrel. There is a mathematical formula that will get you close. It uses your barrel length and bore diameter , and average burning rate of black powder to get you close, but it is only about 80% accurate. When I used it for my Hawken flinter with a 24 inch barrel it come up around 50 grains, and 72 grains was what the paper test showed. It shot accurately from 50 to 70 grains, so for hunting I shoot 70 in it. On my cap lock Hawken 50 cal, the formula said that 69 grains was the max and it had a 26 inch barrel, the paper test showed 70 was the max for it. The formula doesn't take into account for rifling depth, load tightness and all the other things that vary from gun to gun.

Best wishes,

Joe

[waksupi]

In smoothbore, I'm running around 75 gr. 3F. In the rifle, 95 gr. 3F. I had one real slow twist .62 that took 170 gr. to shoot well. Accuracy, and your shoulder will tell you when you have reached max.

[HARRYMPOPE]

In smoothbore, I'm running around 75 gr. 3F. In the rifle, 95 gr. 3F. I had one real slow twist .62 that took 170 gr. to shoot well. Accuracy, and your shoulder will tell you when you have reached max.

what are the bore dims? I believe GM run about .615.Do you think a .600 ball and thin patch would be OK? In my 12ga i have to use a thick patch and (.690)ball to get good accuracy.

George

[waksupi]

I couldn't tell you the dimensions of a GM barrel. I shoot .595 in three different guns, the rifle takes a thicker patch. You may well run into this type variation if you have a double gun.

[Good Cheer]

Have a .600 Lee mold and working out the difficulties with the rifled barrel. Pretty hard to get accuracy without a mallet.

[SamTexas49]

I had a .62 cal Sharon Full Stock Hawken (way back in 70s). Only 1" across flats. For target shooting I used 60gr FFg for range, 25 to 100 yd (just adjusted sight hold for range (50yr was "6" hold) On Steel targets it was great! 100yd sheep were knocked over as hard. 25 yrd squirrels had to be retrieved at another 10yd past . Hunting I simply used double call (120gr) with no intentions of shooting past 75yd. Never had chance to see how it did on game sadly but I had no doubt it punch through anything up to Elk. A funny story back to steel. While shooting 25yd squirrels , I had cleaned 4 and was shooting 5th, a friend was with me observing, I took the shoot at the 5th squirrel, missed (!) but the squirrel just rotated on its base 90' ! All we could figure is the air turbulance from the ball passing by was enough to disturb it!