4013 etc Single Recoil Spring question

[ACEd]

Looking for resources for replacing recoil spring on early 4054 with single recoil spring - same as early 4013, 4014, 4053, 4054 but different from late 4013 etc and all the 4013TSW etc with smaller diameter guide rods and dual spring setup (which is still available).
Anyone know spring rates and lengths for 4013/4054? Anyone know the effective spring rates for the late 4013 / 4013TSW dual spring setup (same as 4516-2 & 4513TSW dual spring).

I am assuming the 3913/6906 springs (15 pound?) would be correct geometry but too soft. Maybe Wolff 3913XP (available 16, 17, 18, 20 pound varieties).
Thanks, Ed

 

[ACEd]

Never mind - I just realized Wolff has springs for 4013 etc single spring configuration in "standard" 16 pound variety plus XP variants.

 

[ACEd]

Still curious as to effective spring rate of double spring setup - or if anyone has the rates for individual springs in the dual spring setup.

 

[BLUEDOT37]

Still curious as to effective spring rate of double spring setup - or if anyone has the rates for individual springs in the dual spring setup.

In my testing the factory dual/nested springs measure right at 20# (red circled below) fully compressed in one of my 4013TSWs.

The ISMI GLC-20 flat springs will also work but they're not quit as strong at 18# (blue circled below).

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