Fellas, i have noticed with the Hogdon H322 in my .38-55 i get a bit of unburnt powder in my barrel. After i fire a fouling shot, my accuracy is quite respectable for my lever action with 1" groups at 100 yards. However, once i get to about shot 15 or so, my accuracy drops off. Is this from unburnt powder in my barrel or from not letting my barrel cool enough??

Mark
Could be the barrel heating up. Some other considerations would be lead bullets vs jacketed, lead or copper build up in barrel. Could simply be a combination of bullet, powder fouling.
Maybe shooters fatigue from a long string of shots.
I've got two lever actions an 1886 in 45-70 and a Rossie 1892 in 45 Colt. Both shoot very accurately when I do my part. I've never seen any indication of groups growing when I've shot long strings off the bench or off hand, due to barrel heat. Shooter's screw ups, shooter's not paying attention, in my experience it's seldom the rifle and most times it's the shooter.
Now I will say my 25-06 is the exception to this and makes a liar out of me. This rifle has two different groups 3/4 of an inch a part. There is slow fire warm barrel group and the rapid fire hot barrel group.
So for what's worth.
Jim

Thank you Jim. That helps.

Shooting to fast will take it's toll on group size. If your rifle bore is more than luke warm to your touch your shooting to fast. The rifle is telling you to slow down or that it needs cleaned after fifteen rounds down the bore. Hunting weight barrels heat up very quickly in warm temperatures and need more time to cool between shots. Few game animals get more than three rounds fired at them under hunting conditions. Hunting groups only rquire three rounds from a stone cold bore. Target rifle shooters will fire as many as twenty rounds to post a five shot group in seven minutes and must have heavy barrels to maintain accuracy.