Will,
Actually fouling the Carrier Block is very very common. Most toggle link rifles can and do regularly foul the Carrier Block. the question is whether it's bad enough to stop the rifle.
It is also very common for that heathen fad smokeless stuff to foul the Carrier Block. Trailboss, actually doesn't play well with petroleum based lubricants and gets gummy pretty quick. Others, not so much. Before being enlightened to the Dark Side, I could run my main Comp rifle most of the season with no more than a drop of oil.
Some 45 rifles blow-by worse than others. Uberti runs their chamber cutters a smidgen on the large side. Very generous. Then there are the other variables, lube, type of lube, enough lube, powder manufacturer, the list goes on. No two rifles are the same.
Then, in our thread's case, it's a 44-40. There should be no fouling issue with the Carrier Block, and there isn't. Just excess wear somewhere in the lock-works. Although, with 44-40 being used as blanks, I don't know if the case mouth actually seals the chamber. If not, it's blowing-by like a 45 and needs a little help. I'm also not necessarily a fan of sanding away enough Carrier Block until it rattles around in the mortice either. I'd think a little maintenance a better plan
Coffinmaker