I recently bought a M 1884 trapdoor carbine and I also own H&R officers model and a Calvary carbine modern replicas. Checking over the original I studied the locking and how the breech thrust is supported by the trapdoor and the receiver. Reading the thoughts of Frank de Haas , he says the close fit of the trapdoor to the receiver supports the thrust and the hinge pin does nothing but provides the pivot for the trapdoor.
I started with the original M 1884 and with the action closed and locked I can get a .022 feeler gauge between the receiver face and the back contact area of the trapdoor bolt and this action is not worn out or in poor condition. So being curious of how my H&R replica rifles measured I was surprised to find them both almost Identical in clearance maybe .001 tighter and they have been fired very little.
So what Frank de Haas says about the close contact between the bolt and the receiver face is not true. I did not try to measure headspace on any of these guns but would guess even if it’s only .004- .005 then when they are fired there is a lot of space that has to close up for the breech thrust to be supported. Even thinking about the slight angle of the rear of the bolt and the mating surface of the receiver the bolt would want to slide rearward and travel upward except for the close fit of the locking cam that keeps the rear end latched.
For the people who own and shoot trapdoors and study their actions , how do you feel the breech thrust is supported ? I like the actions design, especially at the front of the trapdoor how it is wedged under the upper hinge supports on both sides that are part of the receiver and how the ejector/extractor works. It must be quite strong and rugged to hold up shooting a large cartridge such as the 45-70.
From what I have read about where the action will fail if severely overloaded is at the receiver ring where it is drilled for the ejector spring and plunger. That tells me the hinge pin isn’t taking much breech thrust and the rest of the action is quite strong 💪. What are your thoughts ?
Jedman