Barrel length has nothing to do with it. TG is a pistol powder as well as a SG powder and it will work. The lead bullets might give you fits with it. TG is fast burning. Fast burning powders can give leading and poor accuracy with lead bullets when used near the top end of the charge data. If you want light loads to cycle the gun and go "bang", TG will work well. If you want to load more along the lines of factory ammo velocties, you might get leading.
For ammo with cast bullets that is closer to factory velocity, Unique, or similar medium speed pistol powders work better in nearly every case.
I would start at the "start" data and only load a few dozen. Shoot them and check your barrel for leading. If you get leading, you can work downward with lead bullets in small increments of say 0.2 grains. Make a few up and see if the leading stops. Don't reduce start loads too much with jacketed bullets because they tend to stick in the barrel if you got too low. Lead bullets are much more forgiving in this respect.
For an accurate plinker/target round, I load a 125 cast bullet with 3.5 Bullseye, which is similar to TG in burn rate. If I use much more than 3.5, even though published data goes higher, I get leading.
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