Mainspring testing

[Curss]

Earlier I read a thread concerning weak mainsprings and a few points were brought up about breech blocks slamming into the back of the guns and peening the frames. I examined my own .30 Luger and a frame that came off a double date Erfurt. I noticed small peen marks in the .30 and serious indentions in the Erfurt frame. I was slightly worried about damage to my beloved commercial Luger, and I wanted to swap out the springs in it for new ones so I decided to do some testing with some mainsprings.

I took a recoil spring pack from Wolff gunsprings and began testing them in my 1920 .30 Luger, and found that none of the springs would function properly in the gun as they were. Changing out the firing pin spring for an extra power spring seemed to slightly improve things, however jamming issues continued. Disheartened, I thoroughly cleaned the pistol and stored it away for when I would have time to experiment once more.

For this batch of testing I determined that perhaps I should tune the springs to properly fire Fiocchi .30 ammunition. Using the tape test to measure recoil, I also applied tape to the peen marks on the inside of the gun to see if and when the breech block would hit the frame.

I once more began testing and found that at least one or two rounds could be fired through the gun using the #38 Wolff mainspring. The #36 spring refused to function so I selected the #38 pound spring and began taking one coil off at a time. There was a marked improvement in functionality when the spring had 18 coils on it. So, I snipped half the coil off and once again test fired it with an original mag and a Mec-Gar magazine that had both been reworked by G.T. Each magazine had 7 rounds in them, and all 14 shots went through flawlessly!!! The tape wasn't mangled and the gun shoots great! The new spring measures just under 3 inches, the old one is 3 1/4 inches.


Here's a pic of the tape test for the breech block peening.