A Question for All Kimber CDP Owners

[BonoVox]

Very cool!!!

[inboost]

For reference as my memory didn't serve me so well.

[KimberDude]

Originally Posted by inboost

For reference as my memory didn't serve me so well.

Wow! I was supposed to change my recoil spring on my Compact CDP II 500 rounds ago.

[inboost]

The Wolff spring set for the Ultra CDP II was delivered today. I successfully assembled and tested my rebuilt recoil assembly on the bench, but will have to shoot it (this weekend) to know for sure if I have a winner. The force results are a bit confusing. I get very consistent data suggesting the springs have even more force at rest position, but less at full recoil position

With the slide at 'rest' position the Wolff springs deliver 6.3 pounds of force vs. the Kimber new unit's 5.9 pounds of force. However, at full recoil position (1.75" of compression from rest) the new Kimber recoil unit delivers 18.7 pounds while the Wolff measures in at 17.3 pounds. The initial force being higher makes sense as of the assemblies I have it's the longest (0.16" longer than the new Kimber set).

From observation I'd say that in this recoil system the inner spring is a much stiffer rate than the outer spring (smaller coil diameter, longer free length, considerably more coils than outer spring). When loaded in the gun the outer spring has been compressed about 0.70" while the inner spring has only moved about 0.12". This means the initial pre-load is primarily set by the outer spring. The inner spring must be a bit weaker on the Wolff if the combined force level of both springs working together come up short even though the initial is higher than the new Kimber unit. Additionally The spring rate must be lower as the new Wolff spring is longer than the used Kimber spring by 0.15" so even though it is compressed more, the force is less.

I guess we'll wait and see how it goes this weekend. Stay Tuned!

[TaxMan]

Originally Posted by inboost

For reference as my memory didn't serve me so well.

What about Custom Models?

[CCWInstructor]

Originally Posted by TaxMan

What about Custom Models?

The 5" barrels don't have a replacement per round count. I do mine at 25,000 rounds.

[X-ffdo]

Originally Posted by sholling

In general the shorter the barrel the more critical the timing and the more important it is to have a fresh spring. I'll say it again, if it's a 3" or a 4" - both of which have known timing issues I'd stay on top of the spring. I choose to change out fairly often because its hard to talk a bad guy into letting you go get another gun in the middle of a gun fight. It also seems pretty silly to skimp on replacing worn out $8 parts when you've invested $1000 in the gun. But that's up to each individual.

Bingo!!!

[X-ffdo]

Originally Posted by CCWInstructor

The 5" barrels don't have a replacement per round count. I do mine at 25,000 rounds.

Did not want to say anything but......I never replaced mine in like 20 years.....but it was a 5 inch. Don't know why I parted with that one. I miss my bare ass GI model.

[X-ffdo]

inboost, when I grow up, I want to be like you!

[PUNK]

Originally Posted by X-ffdo

inboost, when I grow up, I want to be like you!

thats what I said a few years ago when I met him for the 1st time.

[inboost]

Thanks guys, it's fun to be me sometimes!

Today I'm reporting on the 4" Kimber guns. My Wife shoots a Pro Carry II HD (full stainless 4" gun). The spring in the gun has approximately 400 rounds on it. I also ordered Wolff's 'XD' spring replacement kit. I built a set of adapters to work with the Ultra tools so I can test the 4" and even full size springs (hopefully 5" tests tomorrow).



The abbreviated results for 4" guns are:

Slide at rest spring load

• Kimber: Used with 400 rounds on the clock = 4.3 pounds
• Kimber: New from unfired gun = 4.4 pounds
• Wolff 'XD' spring exclusively wound for 4" Kimber = 7.5 pounds

Full recoil compression spring load (Stock rating is 18 pounds)

• Kimber: Used with 400 rounds on the clock = 17.4 pounds
• Kimber: New from unfired gun = 17.8 pounds
• Wolff 'XD' spring exclusively wound for 4" Kimber = 20.0 pounds

Free lengths of springs

• Kimber: Used with 400 rounds on the clock = 3.48 inches
• Kimber: New from unfired gun = 3.46 inches
• Wolff 'XD' spring exclusively wound for 4" Kimber = 4.26 inches

So I'd say at 400 rounds shot (out of 800 recommended) the spring has not deteriorated at all. Greg will be running my Wife and I through advanced in a few weeks (Oct 19th) and that will put another 400 rounds on this spring. I'll pull and test it and let you know what happens

[BonoVox]

Inboost you are the man!

Pretty cool stuff and somewhat surprising too.

Look forward to your next update!!

[inboost]

I ran a test this morning on the 5" Colt Government gun that I've had since the beginning of time. The unfortunate thing is that I picked up a Wilson full-length guide rod when I purchased the gun and it came with two (or three?) springs. I know that throughout it's life this gun has had a shock-buffer and various combination of springs with absolutely no round count on them, so I didn't learn very much. The good news is that my test rig was successfully able to test the 5" spring, and that the one in the gun came out at 16.1 pounds (which is the correct stock value). The new Wolff replacement delivered 16.8 pounds but that will relax a little after it gets shot.

Kimber's suggested replacement strategy is found in their manual on their website:



Note about the Wilson shock-buff and similar 'anti-battering' devices:

These plastic/rubber bumpers go on the spring guide rod first and then you load your spring on top of it. The idea is that the back of the slide hits a cushy stop instead of a steel plate thus decreasing the battering damage people observe when using the incorrect spring for the job. This can actually do more harm than good, as many times the springs in these guns are near coil bind (a situation where the spring is compressed to the point that it's just a steel tube). The bumper reduces the room a spring has to compress in by it's thickness (Wilson is 0.105"). Coil bind is really hard on springs and takes their energy storage capacity out quickly. Once hurt the weakened spring allows the slide to hammer through the bumper and you're left with a nicely punched piece of rubber/plastic and some battering damage. My observation in my gun is that the compressed full recoil position for the new Wolff spring is ~1.45" long but coil binds at ~1.35" leaving 0.100" left for the recoil buffer which is actually 0.105" thick (but soft, so it will compress). This is a static measurement, so no dynamics like inertia and flex come into play. I'm pretty certain this combination would put the spring in coil bind when shot and quickly reduce the spring's strength. Moral of the story, if you must use these devices be sure to determine if there is room for them first. If in doubt, leave it out!

[inboost]

Perivouslty I posted in reference to the 4" Kimber guns that:

Originally Posted by inboost

Full recoil compression spring load (Stock rating is 18 pounds)

Turns out this is a mistake! In re-reading my notes the stock spring force for the 4" gun is 22 pounds, NOT 18 pounds (that was for a .38 super gun). This puts the springs I measured at a much lower rate than advertised even when brand new! So I called in to Wolff and spoke to a patient and helpful tech who gave me the scoop:

"Kimber installs the 22# outer (larger) spring of a Colt Officer's model in their 4 inch guns, our stock number 49022"

This is a problem because the Officer's Model is a 3.5" gun with an appropriately smaller working space. This equates to a spring that exerts a much lower force when the slide is at rest resulting in a gun that has difficulty closing on return to battery. The amount of compression is also less so the force at full recoil position is proportionately lower. Wolff designed and released their "XP" spring which delivers a 20 pound force with a substantially higher in-battery force as seen in my testing (they added five coils and stiffened the spring). My Wife's gun actually does have some trouble going back to battery and requires a gentle bump on the slide from time-to-time so I'm looking forward to testing out the new "XP" spring.

[moosehog]

Originally Posted by inboost

For reference as my memory didn't serve me so well.

Help me understand why the 4in compact/pro requires more frequent changing than the ultra 3in model. I would have thought just the opposite??