I loaded mine the same way with the capper thru the hammer slot. Works great, but I don't think Sam Colt would approve ... I bought a brass frame model 51 specifically for a .22 cal. Kirst conversion cylinder & it didn't have enough clearance to load or unload. Kirst instructions were general enough to mention using a sanding drum to reshape the loading port.
The Dremel sanding drum with first coarse, then medium, and then an abrasive-impregnated rubber drum to remove tool marks, and on to some 600 grit wet/dry paper, then finally a buffing wheel & it looked great - not anything like a "done-it-my-ownself-at-the kitchen-table" quality you'd expect using a Dremel. Of course it took 6 hours to complete, but much of that was waiting for the battery on my cordless Dremel to recharge.
I was so impressed with myself that I did a repeat on the steel frame, too. A magnet on the table makes clean-up easier ...
I finished the brass frame with some Brass Black. Over dirty metal surface, it kinda looks like case hardening, but doesn't look to be very durable. The brass black on the steel loading port gives an acceptable finish to knock down the otherwise bright mirror finish on the steel frame work.