How to measure spring strength? Help!

[Slamfire]

I have been shooting a Les Baer Wadcutter in NRA competition and I am want to install a new recoil spring. How do I measure the spring strength in the M1911? I cocked the hammer, so the hammer spring would not give a false reading, tied a string around the pistol, string being on the recoil plug, and with a fish scale attached to looped string, measured around 13 lbs just as the slide started to move, and 18 lbs just before lockback. Which value is the correct value for the strength of the recoil spring?

From what I know, there are 13 lb recoil springs, and there are of course, 18 lb recoil springs. Which do I have?

 

[ulflyer]

Slamfire, just guessing on my part, but it seems as a spring compresses it reaches its
max strength, thus, 18lb would be right. Again, I'd guess a Baer would come new with an 18 to 20lb spring. I'm sure you'll get a good answer shortly.

 

[pblanc]

This might help:

http://www.brownells.com/userdocs/documents/bt002003.pdf

 

[Slamfire]

Thanks for the Brownell's link. From what I read there, the spring is to be measured compressed.

 

[jmorris]

I have made them from 1"box tube like the brownells one linked above but if you don't care about swapping them around...

Put an empty mag in the pistol and lock the slide back, then take a fishing scale that has a "marker slider" that stops at the max force and place the tip of the hook into the firing pin hole. Now slowly increase force until the slide just comes off the stop and release the force.

Now read where the marker stopped, 15#'s in the case of this one.



It is as repeatable as any other method I have used, just not as convenient if I have a bunch to test. All measurements are obviously compressed.

 

[tark]

Hi, Slamfire. I never assembled when I worked for Les, but I'm pretty sure the Wad guns came from our shop with a 13# spring. An 18# was standard for the 5" 45s, with the wad guns getting the lighter spring to adjust for the lighter loads.

Trying to measure the weight of a worn spring is....well.... measuring the weight of a worn spring! You will get a number for a worn out spring which is no longer up to the task....

Call Brenda at the shop. She can tell you what weight spring you should put in the gun.

 

[Slamfire]

Hi, Slamfire. I never assembled when I worked for Les, but I'm pretty sure the Wad guns came from our shop with a 13# spring. An 18# was standard for the 5" 45s, with the wad guns getting the lighter spring to adjust for the lighter loads.

Trying to measure the weight of a worn spring is....well.... measuring the weight of a worn spring! You will get a number for a worn out spring which is no longer up to the task....

Call Brenda at the shop. She can tell you what weight spring you should put in the gun.

I did, and she said the Wadcutter came with a 13 lb mainspring. I ordered two, plus an extra firing pin and spring. The Wadcutter has a unique firing pin and it if breaks, the pistol is down, so I thought I would order one.She also mentioned that the Wadcutter with the sight rail on the slide should not be fired with bullets weighing more than 200 grs, for concerns of slide cracking. Thanks to all for the good advice