Couple of questions

[mrerick]

Yes - there are people that literally wrote the book on spring technology. It's actually a very precision and moderately complex thing...

This write-up is useful for understanding how our Luger recoil springs are designed and work:

http://springipedia.com/compression-stress-spring.asp

The recoil spring in a Luger is called a compression spring. These springs are actually designed to take a "set" when they are installed in an application (like around the guide rod that holds a Luger recoil spring).

Since they are actually designed to take a set, they get shorter than they were when they were manufactured. Once this "set" is taken, they generally do not change dimension again in their lifetime.

The compression principal of a Luger recoil spring is the same as that of the coil suspension springs that hold up a car body. You don't see these lose power and tension over their lifetime unless they are abused (by constantly carrying too heavy a load).

Over the life of the Luger, the requirements for the recoil spring changed as the ammunition, the receiver geometry and the length of the barrel changed. The strength of ammunition ignition and the length of the barrel contribute to the force that the recoil spring must absorb, both in intensity and in pulse shape. Various small changes in the geometry of the Luger receiver also changed spring requirements.

Marc

[danielsand]

Originally Posted by mrerick

Yes - there are people that literally wrote the book on spring technology. It's actually a very precision and moderately complex thing...

This write-up is useful for understanding how our Luger recoil springs are designed and work:

http://springipedia.com/compression-stress-spring.asp

Since they are actually designed to take a set, they get shorter than they were when they were manufactured. Once this "set" is taken, they generally do not change dimension again in their lifetime.

The compression principal of a Luger recoil spring is the same as that of the coil suspension springs that hold up a car body. You don't see these lose power and tension over their lifetime unless they are abused (by constantly carrying too heavy a load).


Marc

This is very interesting to say the least. I am VERY familiar with automotive coil springs (used to own two car dealerships in the 90s). And it's absolutely true that they almost never need changing. MY reasoning is,....shock absorbers. They take the pounding, and in return get used up.

IF the gun springs take the set, and never change from that point on, they would never have to be changed. That's not my experience with recoil springs.

This old Erfurt came to me with marks on the back of the frame. I thought,..... OK, smeone shot it with something hot. Then I applied the tape, and shot it with Federal 115gr (that's about as mild as 9mm factory ammo goes these days), and it marked the tape! I realize that this ammo is few FPS faster at the muzzle, than the original Georg's load, but such a little difference should not mark the frame. Since I saw few shooter Lugers without that mark, I concluded that mine has a weak spring (since all shooters I saw used the factory ammo, and not "designer" handloads).

Couple of days ago (when I started this "spring quest"), a friend brought his shooter, and his was not marking with the same ammo. I pulled the springs from both of them, and there was no visible difference between them. I don't have any means of calibrating the springs to actually compare them, and I decided to order 40# spring, and give it another tape test.

Only few things can happen from this point,.......the spring will be too stiff, and I'll have the weapon "short stroking", failure to feed, or failure to eject. Extraction should not be affected, but the short stroke, or failure to eject might cause the stove pipe.

Simple logic tells me that if the weapon goes too far back in recoil,....the recoil spring is too weak. IF the 40# is too strong, I'll have to get the standard 38# spring, or give it a run with some 124gr loads.

I'll report back.

[sheepherder]

Originally Posted by danielsand

Then I applied the tape, and shot it with Federal 115gr (that's about as mild as 9mm factory ammo goes these days), and it marked the tape!

Daniel, you don't say what the tape looked like...Was it just 'kissed' by the toggle, or was the tape mashed flat???

I'm not a big proponent of the tape test. I've attached a pic of three of my Lugers showing the impact area of the rear toggle 'ducktail'...

First is a 1900AE, very pronounced impact area, you can actually feel the depression with your fingernail...Indicative of many years of 'hot' load hammering (or a failed mainspring * )...

Second is a 1937 S/42 [Mauser] with what I consider 'normal' wear...

Third is a refinished commercial which was fired only 10 - 15 times w/'target' loads following the re-blue...

If your frame is close to my second frame then I would not be too concerned about firing Winchester White Box 'target' ammunition in it...

* 1900's have a flat 2-piece mainspring

[danielsand]

Originally Posted by sheepherder

Daniel, you don't say what the tape looked like...Was it just 'kissed' by the toggle, or was the tape mashed flat???

I'm not a big proponent of the tape test. I've attached a pic of three of my Lugers showing the impact area of the rear toggle 'ducktail'...

First is a 1900AE, very pronounced impact area, you can actually feel the depression with your fingernail...Indicative of many years of 'hot' load hammering (or a failed mainspring * )...

Second is a 1937 S/42 [Mauser] with what I consider 'normal' wear...

Third is a refinished commercial which was fired only 10 - 15 times w/'target' loads following the re-blue...

If your frame is close to my second frame then I would not be too concerned about firing Winchester White Box 'target' ammunition in it...

* 1900's have a flat 2-piece mainspring

Mine looks like your middle one. Two spots where the blue is gone, no indentation. 40# spring is on the way (cheap!), and we'll see what happens. My pistol also has PRONOUNCED (to the point of the metal deformation) impact areas on both "ramps" (a little more on the left than right). I got the pistol in this state. Both toggle knobs have the blue worn off at the area of the impact. This did not happen with me firing 50 rounds out of it, and it shoots to POA. Next time I fire it, I'll clean the metal with alcohol, and appy the "white out" (the tape kind) on all this, and observe. ANY impact should be easy to see.