Kimber .22LR conversion break in: Is there light at the end of the tunnel?

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Chuck Dye

Dec 24, 2002
Oregon-The wet side.
The Kimber .22LR conversion goes on an older Springfield Armory cheapie frame. Any high velocity ammo with bullets less than 40 grains will just not run the gun reliably. Failures run the gamut, failure to extract, stove pipes, slide travel to ejection but not to new round pick up, any or all of the above. Some brands will begin to run OK two to four rounds into the magazine, others are a nuisance from start to finish. High velocity 40 grain rounds are better, but many will not run the gun until the magazine is down two to four rounds. Standard velocity rounds need not apply. The problem seems to be diminishing with use.

Has anyone else had this experience? How many rounds did your conversion need before it began to run well with most HV ammo?

Has anyone any experience with changes to the action which solved the problem without compromising .45 ACP functioning?

(For comparison, I had two Ceiner conversions (a burglar got’em) which ran any high velocity ammo flawlessly from the start (I never tried any standard velocity ammo in either.))

22 conversions are blow-back operated, so it's operating pressure vs spring pressure. There are 2 springs to contend with, the recoil spring in the slide and the hammer (mainspring) spring. The standard 23# hammer spring generally requires high velocity rounds and the 17# hammer spring can generally use the standard velocity rounds.

This is precisely how my Kimber 22 kit functions. Kimber also recommends lubrication at specific points. Mine works well on Kimber and Rock Island 45 frames, both have 17# mainsprings.

Question is did you use the Ciener kit on the same frame you're using with the Kimber?
Yes, the Ceiner kits ran flawlessly on the same frame.

Thanks for the tip on the mainspring. Obvious, but I was unaware of the numbers. Does a 17 lb. spring provide reliable centerfire ignition?

Well, the problem is solved. It apparently took an integrated fix of several hundred additional rounds fired, perhaps two thousand or more manual slide cycles, switching lubrication, and switching to a 17 pound hammer spring, but the conversion is now running even with hollow points.
My Kimber .22LR conversion kit was used mostly on my Kimber Warrior, and now on my Colt Series 70 reissue. (Sold the Warrior) Back to topic, I never had a break-in period with it. It has run well from the get-go. Some of the hotter, and cleaner ammos run better. That said, Remington Thunderbolts run perfectly well at a low cost. I get no failures until the latter part of 2 boxes run. Anytime that it has been problematic, it has been that the chamber needed cleaning out the grime with nothing but a clean cloth, or a spray-out. It does have an exceptionally tight chamber, and is very accurate.

Glad to hear it. I feel the problem with many 1911/22 conversions is running the stock 23# mainspring and standard velocity ammo. My guess is you should have noticed a better trigger pull with the 17# spring.
Yes, the trigger pull seems mildly improved, though I'd rather gauge it before declaring that as fact.

Standard velocity still does not run the gun but that is not a problem. As the conversion is for practice and plinking, the real issue was to get the gun running without nuisance on the cheap stuff.

Thanks again for the tip on the mainspring (might have done without the "Well, DUH!" moment, however!)
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