Quote Originally Posted by ptdunk View Post
Along with the fine level of trigger adjustment I think the spring being in three well finished sections is a strong sign of an intention to experiment with different setups, and in fact if the power was to be changed with different spring section combinations then the trigger weight would have to be changed accordingly to give a safe amount of sear engagement in relation to the strength of the spring. Not something that someone just making a project gun would probably consider...
Maybe having to remove the sideplates to adjust the trigger meant that the user could get a visual impression of sear engagement etc. while adjusting the trigger, which may have been more useful for experimentation than simply adjusting the trigger blindly from the outside? Just an idea.
Thanks Matt. Your comment about being able to alter the spring power and at the same time investigate the effects of sear/trigger changes is an interesting point and it prompted me to try it out for myself.

This is the pistol with the three springs removed. These are nicely finished and are a precise fit both within the chamber and around the barrel. I am pretty sure this use of multiple springs was deliberate, and not a case of grabbing some springs that were handy.





If you remove one spring, the slack is easily taken up by the muzzle nut, as the muzzle has been given a longer threaded section than normal. This reduces the power a fair bit and makes cocking noticeably easier, but it still puts out slugs at a reasonable velocity.




This is the gun with the three springs in.




Adjusting screw (A) alters the angle the sear head makes with the piston and you can vary the trigger pull from heavy to a risky hair trigger. Adjusting screw (B) also helps make the trigger pull lighter or heavier, but in a different way. You could have a lot of fun trying out all the options, with two and three main springs. This reminds me very much of the sort of thing Gerald Cardew would do.

Whoever made this gun and whatever his reason for making it, I don’t somehow see it as “just something knocked up for a youngster by a father at work” as Ed suggested.