James,
The masking tape routine is something that was talked about on this forum years ago. Tis not a new idea, really do not remember who suggested such specifically here, but I borrow the idea from time to time on my pistols.
On the rear of the Luger pistol, the rear toggle section that houses the integral rear sight, rotates upward during the firing cycle. If you pull the toggle to the rear manually, you will see at the rear toggle/frame interface, probably two marks made into said frame just above the landyard ring from the over rotation of the rear toggle section. Kinda like a tuffy beaver took a bite out of the frame in some light.
The recoil spring is supposed to retard the action of the toggle to the rear. The frame is kinda a last resort in my opinion. The condition of the recoil spring, and the fitment of the toggle train to the receiver retards the rearward movement. There are other parameters of cause of movement to the toggle as well. A simple concept for longevity of said parts is to use ammo that allows just a touch(if that) onto the frame from the two protrusions from the rear toggle section. Kinda a balancing act of a type.
You see Lugers all the time with heavy duty indentations on their rear frame above the landyard loop. This is usually due to hot loads of whatever source or a weak recoil spring. Choosing ots ammo or reloading can tune the firing cycle to reduce the bite into the frame. Ever feel an auto pistol that bites into your hand? That is metal on metal abrupt stop of the slide onto the rear buttress. I have one receiver that I bought when I was much younger, was purchased cracked, I believe from such events.
Anyone can overload the Luger with hot loads, not much problem to do such, one sees it all the time. Yeah, it will work pretty good, but the stress on the pistol will eventually cause failures of parts somewhere. I do not believe a hot load is necessary for a 100 year old pistol; but just my own opinion.
Not very scientific or anything, but has some practicality to it, the tape marker observation. If the tape is smeared off the frame, one would tend to think the toggle is moving too fast and way too far back, overriding the natural designed-in forces of the mechanism. My shooting Lugers will just mark the tape with my reloads. I have not bought factory 9mm ammo for many years, but just my choice, I can control things to my liking with my handloads. If I mess up, no body to blame but the guy behind the riggin.
If you do a search, I am sure you will find the tape method explained in more detail than this little note. Really not a bad indicator of system parameters, and not too expensive either. Mileage with the tape marker routine will vary of course with the user.
I have no idea if your 147gr purchased load is safe or not. I feel that the 147 is a bit heavy for the Luger but solely an opinion from a casual reserver. Most folks here like the 115gr Winchester white box stuff, just from observing the threads over the years.
Rick W.
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