Here's my take on a dry-fire device, but for my Hammerli 208's. For M-41's, this will work just as good, but sizes may need tweaking.

I start with a rubber "foot" for DIY cabinets. Size is 3/4" diameter by 3/8" thick (.750 x .375"). 

Using a single edge razor blade, I cut the foot in half, bisecting the .750" dimension. I then thin the .375" thickness so that it's just very slightly (approx .010") thicker than the width of the side-to-side hammer cleaance slot in the slide. This allows the dry fire device to fit up into the slide and be held in by a friction fit, so that it doesn't fall out of the pocket when the slide is cycled to reset the hammer.

I also cut a firing pin clearance pocket in the front of the device, and a small pocket in the rear so that you can get in there with a pointed object to pry it out of the slide when you are done with a dry fire session.

When it's in place, the hammer falls just a slight aount when the trigger is pulled, and is stopped by the rubber bumper. The slide only needs to be slightly retracted so the hammer is recocked by the bumper. Then you're ready for the next "shot".

I've been using these for years and they work 100% perfect. I can't see that there is any stress on the hammer or the firing pin (firing pin is not touched by anything due to the pocket in the front of the bumper) and have never had any wear or breakage while using it.

I can't remember where I got my original feet, but these from McMaster-Carr will work fine: https://www.mcmaster.com/9540K703/

If you need a different size, you can start here: 
https://www.mcmaster.com/products/feet/unthreaded-bumpers-6/