P08 Recoil Spring Ratings

Scott H. · 04-20-2004, 11:19 AM

I'm not having any problem but rather trying to educate myself about P08 recoil springs. I have always heard that on the pre WWII 9mm P08 that the springs were weaker than the WWII guns. Is this true? If true what are the factory specifications for the pre WWII 9mm Luger vs the WWII 9mm Luger? I am just curious as I have always used Wolff 38 pound springs with excellent results with all 9mm ammunition.

Here is where I am really curious - the P08 in .30 Luger. If I ever do need to replace a recoil spring what do I use? What is the factory specification for this caliber? Would the Wolff 36 pound spring be to heavy for the .30 Luger? Would I need to cut down a Wolff spring? If so how much? Any comments from those with more knowledge than myself are appreciated! Thanks.

unspellable · 04-20-2004, 06:31 PM

Both calibers used the same recoil spring in the old model with the flat spring. The new model has two different springs for the two calibers. Around the same time the 9 mm began to be loaded a tad hotter.

Cutting springs is more complicated than it looks at first glance. There are three important spring parameters, free length, per-load force, and loaded force. Spring suppliers, including Wolff, ten to provide only the last figure. Wolff springs have a free length much greater than the originals. While this is not desirable in itself it makes them the best candidate for cutting.

The pre-load force must NEVER be less than 25 lbf. This controls the final closing of the action and if the action stops just short of locked it is possible to fire the Luger with very unpleasant consequences.

For the 7.65 mm start with the softest of the three Wolff springs and see if the action will lock open. Trim a little bit off at a time until you arrive at this point. The 7.65 mm spring will want to be only 2 to 4 lbf lighter to match the original. You'll need to take a little more off for Winchester or Fiocchi loads.

I have the original factory specs for the 7.65 spring, I'll dig them out.

Scott H. · 04-20-2004, 08:14 PM

Thanks for the information. I am writing notes in a book for future reference. This is the type of information that I find difficult to come by when I need it for a project. Thanks!

unspellable · 04-21-2004, 08:48 AM

Shot myself in the foot. That's what I get for trying to quote from memory when in a hurry. Dug out my stuff, here's the correct data:

Original DWM recoil spring for the 7.65 mm

19 turns

Free length: Nominal 85.00 mm, Min 82.50 mm, Max 87.50 mm.

Pre-load at 50.00 mm, min 15.43 lbf, Max 19.84 lbf

Loaded at 34.00 mm, min 33.07 lbf, Max 36.38 lbf

Note that in the previous post I misquoted the minimum safe preload. When cutting a spring, the preload drops faster than the loaded force. Since the pre-load force has a large influence on the final closing you can get into trouble. The Wolff spring has a free length much longer than the original so you can get away with cutting it.

The spring must completely close the action every time without fail regardless of load. This is a safety issue as the Luger can be fired with the action not quite locked. This makes the minimum safe loaded force 27 lbf in a standard length uncut spring for either caliber, no matter how light the a squib load.

Reliable functioning will depend on having cartridge length match the magazine as well as the impulse matching the recoil spring. The Winchester load is a tad lighter than the original, the Fiocchi lighter still.

Don't forget the main spring. (The one inside the breech block that drives the firing pin.) This one has an influence on final closing also. The loaded force should be 4.5 to 7 lbf.

testing the recoil spring: First try Thor's recommendation that a singly loaded cartridge should leave the hold open engaged every time. To fine tune, place a double piece of masking tape across the rear of the frame. In a perfect world the tail of the rear toggle link will dent the masking tape without cutting it. There is probably too much shot to shot variation to do this every time, but you get the idea.

Scott H. · 04-21-2004, 10:10 AM

Thanks unspellable this is EXACTLY the type of information that I was looking for. As I said earlier this type of information is difficult to come by when it is needed. I will make note of this information. I'm sure that I will use this information as I am always looking for "project" Luger's that need a new home. Thanks again!

04-20-2004, 11:19 AM	#1
Scott H. User Join Date: Oct 2003 Location: The Great Northwest Posts: 66 Thanks: 10 Thanked 1 Time in 1 Post	P08 Recoil Spring Ratings I'm not having any problem but rather trying to educate myself about P08 recoil springs. I have always heard that on the pre WWII 9mm P08 that the springs were weaker than the WWII guns. Is this true? If true what are the factory specifications for the pre WWII 9mm Luger vs the WWII 9mm Luger? I am just curious as I have always used Wolff 38 pound springs with excellent results with all 9mm ammunition. Here is where I am really curious - the P08 in .30 Luger. If I ever do need to replace a recoil spring what do I use? What is the factory specification for this caliber? Would the Wolff 36 pound spring be to heavy for the .30 Luger? Would I need to cut down a Wolff spring? If so how much? Any comments from those with more knowledge than myself are appreciated! Thanks.

04-20-2004, 06:31 PM	#2
unspellable User Join Date: Jun 2002 Location: Iowa Posts: 768 Thanks: 0 Thanked 19 Times in 11 Posts	Both calibers used the same recoil spring in the old model with the flat spring. The new model has two different springs for the two calibers. Around the same time the 9 mm began to be loaded a tad hotter. Cutting springs is more complicated than it looks at first glance. There are three important spring parameters, free length, per-load force, and loaded force. Spring suppliers, including Wolff, ten to provide only the last figure. Wolff springs have a free length much greater than the originals. While this is not desirable in itself it makes them the best candidate for cutting. The pre-load force must NEVER be less than 25 lbf. This controls the final closing of the action and if the action stops just short of locked it is possible to fire the Luger with very unpleasant consequences. For the 7.65 mm start with the softest of the three Wolff springs and see if the action will lock open. Trim a little bit off at a time until you arrive at this point. The 7.65 mm spring will want to be only 2 to 4 lbf lighter to match the original. You'll need to take a little more off for Winchester or Fiocchi loads. I have the original factory specs for the 7.65 spring, I'll dig them out.

04-20-2004, 08:14 PM	#3
Scott H. User Join Date: Oct 2003 Location: The Great Northwest Posts: 66 Thanks: 10 Thanked 1 Time in 1 Post	Thanks for the information. I am writing notes in a book for future reference. This is the type of information that I find difficult to come by when I need it for a project. Thanks!

04-21-2004, 08:48 AM	#4
unspellable User Join Date: Jun 2002 Location: Iowa Posts: 768 Thanks: 0 Thanked 19 Times in 11 Posts	Shot myself in the foot. That's what I get for trying to quote from memory when in a hurry. Dug out my stuff, here's the correct data: Original DWM recoil spring for the 7.65 mm 19 turns Free length: Nominal 85.00 mm, Min 82.50 mm, Max 87.50 mm. Pre-load at 50.00 mm, min 15.43 lbf, Max 19.84 lbf Loaded at 34.00 mm, min 33.07 lbf, Max 36.38 lbf Note that in the previous post I misquoted the minimum safe preload. When cutting a spring, the preload drops faster than the loaded force. Since the pre-load force has a large influence on the final closing you can get into trouble. The Wolff spring has a free length much longer than the original so you can get away with cutting it. The spring must completely close the action every time without fail regardless of load. This is a safety issue as the Luger can be fired with the action not quite locked. This makes the minimum safe loaded force 27 lbf in a standard length uncut spring for either caliber, no matter how light the a squib load. Reliable functioning will depend on having cartridge length match the magazine as well as the impulse matching the recoil spring. The Winchester load is a tad lighter than the original, the Fiocchi lighter still. Don't forget the main spring. (The one inside the breech block that drives the firing pin.) This one has an influence on final closing also. The loaded force should be 4.5 to 7 lbf. testing the recoil spring: First try Thor's recommendation that a singly loaded cartridge should leave the hold open engaged every time. To fine tune, place a double piece of masking tape across the rear of the frame. In a perfect world the tail of the rear toggle link will dent the masking tape without cutting it. There is probably too much shot to shot variation to do this every time, but you get the idea.

04-21-2004, 10:10 AM	#5
Scott H. User Join Date: Oct 2003 Location: The Great Northwest Posts: 66 Thanks: 10 Thanked 1 Time in 1 Post	Thanks unspellable this is EXACTLY the type of information that I was looking for. As I said earlier this type of information is difficult to come by when it is needed. I will make note of this information. I'm sure that I will use this information as I am always looking for "project" Luger's that need a new home. Thanks again!