Loaded some 300gr jacketed bullets to shoot in my trapdoor. Some with 8gr Unique and some with 32gr of 3031. With both of them I am getting powder marks on my firing hand and something dusting my left cheek. The cases are extremely smoked. Are these loads so lite that the case isn't sealing up the chamber? The gun seems in real good shape to me but seem to be getting a little blowback from somewhere. I have been using safety glasses after the first one! Thanks
Richard

Certainly sounds like it.   With only 8 grains of Unique, I'd be concerned that a jacketed bullet might not leave the barrel.   And at 32 grains, 3031 is operating well below its' optimum pressure.   

Annealing the necks might help.   Bigger charges would also.   

For a gallery load, a plain cast bullet would be much a better option.  Even loaded light, jacketed bullets are going to be hard on that old soft steel barrel.   

A powder that gives a quicker pressure rise would also help.  Eight grains of Red Dot would be my choice, rather than Unique.

Thanks for the response everyone. I believe that confirms what I thought. Thanks
Richard