The Tape Test

[4 Scale]

As discussed in this thread http://forum.lugerforum.com/showthread.php?t=37272
a procedure called the "tape test" can be helpful in assessing Luger function.

Objective is to see if the rear of the toggle is striking the frame on recoil, and if yes how hard.

Procedure that I use:
1. Load the pistol with three rounds, to accommodate variations in load strength (I use commercial loads).
2. Chamber a round and put the pistol on "safe". Apply tape to the rear of the receiver. Acquire target and move the safety to fire position. As Dwight points out in the other thread, this sequence is needed to make sure the tape is not touched when chambering the first round.
3. Fire the pistol and check for indentations.

Toggle #53 is 9mm 1938 Mauser, Winchester White Box 115gr. ammo. I view the strike mark on this frame/tape as a benchmark, as the strength of the recoil spring was carefully calibrated. Originally, the toggle was not striking the frame and the pistol was not holding open on last round. I removed 1/2 coil from the mainspring and re-tested. I continued this sequence until I began getting strike marks (hold open then operated correctly as well). As I recall I had to remove 1 1/2 coils to achieve proper operation.

Toggle #94 is a Model 1906, using Prvi Partisan 93gr. ammo. I view the tape mark as acceptably light. Using Fiocchi 93gr. ammo, there was no tape strike and the pistol did not hold open on last round. So, the tape test showed which brand of ammo this Luger prefers and why.

I find the major value of the tape test is determining if any strike at all is occurring. So far, I've not observed a tape indentation that seems "too strong"; however I'm not sure exactly what that would look like.