Your doing an UNBELIEVABLE job here. Its awesome.
Bravo.
I cant tell, because i can never tell if i can see all the pictures (work firewall) but in case you havent covered the 'split trigger guard' I have a suggestion, and its probably too late for this one, but would probably be able to make it in if you ever redo the project.
Cut a large piece of aluminum or stainless since you have a pocket machinist) the thickness of the trigger guard 'gap'.
Make one end the shape of the trigger area, and the correct thickness, and make it long enough so it gets quite a ways away from the model its self. Make it stick out of your mold.
Place it in, pour the mold and then when you demold it the area should be hollow and not need any trimming. Its possible I cant see other images you posted, so seeing as your probably better than I am at this, you probably already have this covered, but this is similar to how I overcame some of my lines in my webley project.
Heres a pic of what I mean. Lets pretend this ISNT the worst fast 3d drawing you have ever seen.
The pink is silicone, the beige is gun, the grey is stainless stock. Placed in before you put the mold together each time for pouring.
Id like to note that this is already probably better than I could have done. But ideas can come from anywhere
Nice work all the way around.