recoil spring ratings

Artsi · 01-22-2003, 07:31 PM

Springs are rated as how many pounds per inch they resist compression. Right?

Let's take say a 36 lb/inch spring and compress it two inches. That would require a 72 lbs of pressure - am I right?
Alternatively for compressing said spring a mere half an inch would take 18 lbs. Right?

I wonder why in the heck am I getting 15 lbs/inch read outs from my own selfmade compression setup for the above Luger 36 lb/inch spring?
I double checked everything. Twice. No obvious errors.

At maximum I had 33,11 lbs hanging there, that made spring to compress 2,17".
What gives?

Commentary most welcome - indeed.

-A.

AGE · 01-23-2003, 01:08 AM

Most likely the Luger spring rating is based on the installed length (whatever that is--unspellable probably knows). It is true, however, that a lot of commercial springs (not firearm recoil springs) are rated on the spring rate (lb/in) not on a particular spring force.

HÃ?Â¥kan Spuhr · 01-23-2003, 01:54 AM

The origial P08 drawing actually states 12 kg instead of 38 lbs.
So here is probbly a difference in how to measure as 12 kg is a lot less than 38 lbs.

Regards HÃ?Â¥kan

ViggoG · 01-23-2003, 02:37 AM

Hello HÃ?Â¥kan,
You are certainly correct, After checking it turns out to be 2.2 lb = 1Kilogram.
which would convert 36 lb = 16.36 Kg.
Artsi,
Some manufacturers rate their springs as "load required to compress the spring to its max working compression". Which appears to be what your measurements seems to be indicating.
HÃ?Â¥kan,
I am glad to see you back as a regular post.
Skoal, My Friend, <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
ViggoG

Artsi · 01-23-2003, 06:04 AM

Ahh... okay, it signifies the total compression rating rather than per inch.

In this light a local spring winding companey (here in Finland) has done a pretty good job with their springs. I've been using their springs in my shooter since I got my P08. (Previous owner had cut and installed a primer striker spring from a Russian 100 year old rifle to work as a recoil spring.)

Domestic spring is noticeably shorter than Wolff spring, but wound from a thicker wire. I had the same 15,05kg/33,11lbs hanging there, that made spring to compress 34,4mm/1,35".
That equates out to 25 lbs/inch rating. A fair improvement over Wolff 36 lb spring.

That spring winding company I managed to find must have had these springs made aeons ago. They had no recollection of making them. Maybe army had ordered them like 30 years ago - who knows.
I have to stop by and buy some more before they destroy/loose the stock of these particular springs.

Thanks for input guys.

-A.

unspellable · 01-23-2003, 10:49 AM

First, the kilogram is a unit of mass, not force. This is a common error. One presumes they mean something like 2.2 lbf or 9.8 Newtons.

The original coil type recoil spring was not a linear spring, hence the force is not directly proportional to the compression.

The "rated" or loaded force should be measured with the spring compressed to a length of 50.00 mm or 1.33858 inches.

The preloaded force should be measured with the spring compressed to a length of 34.00 mm or 1.96850 inches.

The free length should be 85 mm +/- 2.5 mm.

The preloaded force is seldom mentioned but is fairly critical to proper operation. This will tend to go wrong if you cut an original spring.

The Wolff springs have a free length longer than the originals and are thus much better for cutting down as the preload will not suffer so much.

For the 7.65 with four inch barrel the preload should be 15.4 to 19.8 lbf and the loaded force should be 33.1 to 36.4 lbf. This may prove to be a bit stiff for current factory ammo. When reducing the spring force, the object is to reduce the loaded force while reducing the preloaded force as little as possible. This is why it is better to start with an over length spring like the Wolff when you start trimming.

I don't have full specs for the 9 mm but preload should be no less than above and loaded force should range from 36 to 40 lbf.

01-22-2003, 07:31 PM	#1
Artsi User Join Date: Sep 2002 Location: Finland Posts: 61 Thanks: 0 Thanked 0 Times in 0 Posts	recoil spring ratings Springs are rated as how many pounds per inch they resist compression. Right? Let's take say a 36 lb/inch spring and compress it two inches. That would require a 72 lbs of pressure - am I right? Alternatively for compressing said spring a mere half an inch would take 18 lbs. Right? I wonder why in the heck am I getting 15 lbs/inch read outs from my own selfmade compression setup for the above Luger 36 lb/inch spring? I double checked everything. Twice. No obvious errors. At maximum I had 33,11 lbs hanging there, that made spring to compress 2,17". What gives? Commentary most welcome - indeed. -A. __________________ A golf course is a waste of perfectly good rifle range. (- someone in the net-)

01-23-2003, 01:08 AM	#2
AGE User Join Date: Jun 2002 Location: Florida Posts: 597 Thanks: 0 Thanked 0 Times in 0 Posts	Most likely the Luger spring rating is based on the installed length (whatever that is--unspellable probably knows). It is true, however, that a lot of commercial springs (not firearm recoil springs) are rated on the spring rate (lb/in) not on a particular spring force. __________________ Al Eggers (AGE) NRA Life Member

01-23-2003, 06:04 AM	#5
Artsi User Join Date: Sep 2002 Location: Finland Posts: 61 Thanks: 0 Thanked 0 Times in 0 Posts	Ahh... okay, it signifies the total compression rating rather than per inch. In this light a local spring winding companey (here in Finland) has done a pretty good job with their springs. I've been using their springs in my shooter since I got my P08. (Previous owner had cut and installed a primer striker spring from a Russian 100 year old rifle to work as a recoil spring.) Domestic spring is noticeably shorter than Wolff spring, but wound from a thicker wire. I had the same 15,05kg/33,11lbs hanging there, that made spring to compress 34,4mm/1,35". That equates out to 25 lbs/inch rating. A fair improvement over Wolff 36 lb spring. That spring winding company I managed to find must have had these springs made aeons ago. They had no recollection of making them. Maybe army had ordered them like 30 years ago - who knows. I have to stop by and buy some more before they destroy/loose the stock of these particular springs. Thanks for input guys. -A. __________________ A golf course is a waste of perfectly good rifle range. (- someone in the net-)

01-23-2003, 01:54 AM	#3
HÃ?Â¥kan Spuhr User Join Date: Jun 2002 Location: Sweden Posts: 282 Thanks: 0 Thanked 0 Times in 0 Posts	The origial P08 drawing actually states 12 kg instead of 38 lbs. So here is probbly a difference in how to measure as 12 kg is a lot less than 38 lbs. Regards HÃ?Â¥kan

01-23-2003, 02:37 AM	#4
ViggoG RIP Join Date: Jun 2002 Location: South Side Virginia Posts: 534 Thanks: 0 Thanked 1 Time in 1 Post	Hello HÃ?Â¥kan, You are certainly correct, After checking it turns out to be 2.2 lb = 1Kilogram. which would convert 36 lb = 16.36 Kg. Artsi, Some manufacturers rate their springs as "load required to compress the spring to its max working compression". Which appears to be what your measurements seems to be indicating. HÃ?Â¥kan, I am glad to see you back as a regular post. Skoal, My Friend, <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" /> ViggoG

01-23-2003, 10:49 AM	#6
unspellable User Join Date: Jun 2002 Location: Iowa Posts: 768 Thanks: 0 Thanked 19 Times in 11 Posts	First, the kilogram is a unit of mass, not force. This is a common error. One presumes they mean something like 2.2 lbf or 9.8 Newtons. The original coil type recoil spring was not a linear spring, hence the force is not directly proportional to the compression. The "rated" or loaded force should be measured with the spring compressed to a length of 50.00 mm or 1.33858 inches. The preloaded force should be measured with the spring compressed to a length of 34.00 mm or 1.96850 inches. The free length should be 85 mm +/- 2.5 mm. The preloaded force is seldom mentioned but is fairly critical to proper operation. This will tend to go wrong if you cut an original spring. The Wolff springs have a free length longer than the originals and are thus much better for cutting down as the preload will not suffer so much. For the 7.65 with four inch barrel the preload should be 15.4 to 19.8 lbf and the loaded force should be 33.1 to 36.4 lbf. This may prove to be a bit stiff for current factory ammo. When reducing the spring force, the object is to reduce the loaded force while reducing the preloaded force as little as possible. This is why it is better to start with an over length spring like the Wolff when you start trimming. I don't have full specs for the 9 mm but preload should be no less than above and loaded force should range from 36 to 40 lbf.