correct recoil spring weight

I have read about using ejected shell distance, measuring the vertical distance between two rapid shots, and using the most use cartridge power factor to pick the correct recoil spring weight. I understand all but the power factor usage. Could someone explain that ?   Thank you.

For me the number one consideration is what usage the pistol is going to be used for. That dictates what type of ammunition you will be using and thus which spring would help shoot reliably. Bullseye shooters shoot mild loads for precise placement and thus use lighter recoil and hammer springs. Action shooters need to use ammunition that meets a power factor and need to use  springs for that ammo. If this is a defensive weapon, leave it more or less stock and shoot the dickens out of it.

In some action shooting sports like IPSC they require your load to meet minimum PF levels.  Major is a PF of 170 Minor over 125.

Power Factor:  The procedure for determining the PF for any load is a simple mathematical formula: Multiply the bullet's weight by its velocity over a chronograph (which will be used at major matches) and divide the resulting figure by 1000.

Common bullseye loads are far short of those numbers and no one really uses it in bullseye. You could use PF # to match loads to a certain spring combo that maybe just ejects a round perfectly.
A 200gr bullet @ 750fps has a PF of 150
You would need to drive a 185gr bullet 815fps to make a PF of 151.
- Dave

Rule of thumb.

Weak enough that the brass clears the gun  and the slide should lock back every time.

Strong enough so that the first and second rounds chamber completely every time and you don't get tired walking around to pick up your brass. 

(Start with too heavy and work down. Brass at 3 to 4 feet away all the time is pretty good for bullseye.) 


CR

One of the spring companies suggest   start light,  go heaver until It does not function (lock back), then go one lighter.  

I find for  bullseye loads a 13 lb recoil spring and 19 lb main spring make for good solid functioning. 

One of the spring companies gives Power factor range for  each spring weight.

https://shopwilsoncombat.com/Recoil-Spring-5-Full-Size-13-Lb/productinfo/10G13/

Click on the product and it will tell you PF.    For example 13 lb is 130 to 150 PF.   They do not cut off the zeros.    

I tried the flat wire springs.  They need a smaller guide rod, but its drilled so you can put a paper clip in it and take the gun down with out turning the bushing at full lock up.    The 13 was too wimpy for me, so I went up to 15 and it works great.  I shoot 200 SWC around 700-750 fps and 185 LSWC around 775 fps.  It just works with the 185s.    Occasionally it will not lock back.

It was the same in my "combat" 45.   I used to run a 15 lb round wire.   I need a 17 lb flat wire to get the same function.

I can't say if  flat wire is any better than round wire.   The 13 lb flat wire is much shorter than the round wire.


David

Looks to me like how "tight" slide to frame fit and even how well the slide pushes the disconnect down and I'm sure other variables will have considerable affect on how much spring weight needed to close the slide. Does the hammer sit flat against the FP stop or just the very top of the hammer touching? Seems the 1911 can have any number of variables affecting spring rates and this without even talking about whats screwed to the top of the slide.
Therefor the big box of springs and a rig to measure (more like compare) them.