Trapdoors

[Wislnwings]

Here's a couple questions for the trapdoor lovers out there. First, if looking at purchasing one, are there any not so obvious things I need to look out for? I recently looked at a 73 rifle in 45/70 and its got me thinking that I don't have one and maybe I should. Also, are there any good books you can recommend on them? If I decide to move forward with a purchase I'd like to do some reading up on them first. The only book in my home library with any info on them is Mike Venturino's Shooting Buffalo Rifles and I'd like to do some additional reading on them.