Hi Power Hammer Cocking Issue

[dearborndevil]

I have an Argentine FM Hi Power, and it has always preformed well for me. I recently installed a new Wolff extra power recoil spring.

I took it out today, and ran into a problem. Every 6 or 7 rounds, the hammer fails to reach full cock when the slide cycles. There are no feeding or ejection problems, but the hammer ends up resting on half cock. I am using a 18.5 lb recoil spring. My loads were some of the hot Pakistani Mk 2z surplus ammo.

Any suggestions?

[PA Rifleman]

It sounds like your new spring is either too stiff, or the ammunition isn't powerful enough to push the slide back far enough to reset the hammer.

Why did you replace the original spring with a stronger spring?

Thx

[Wiley-X]

You might want to think about replacing the hammer spring with a lighter one. Both the recoil spring and the hammer spring retard the motion of the slide. You've unbalanced the system.

[dearborndevil]

I recently purchased a quantity of the Mk 2z surplus ammo, which is actually pretty hot stuff. It was designed mainly as a submachinegun load. Some of the older Inglis built Hi Powers in British inventory were cracking slides with this stuff. The Argentine version is built with a much heavier slide, with no scallops at the front. I feel that with a slightly heavier spring, it can digest the 2z ammo, along with the amount of +P stuff I run through it.

One thing I did notice while cleaning it today, was that several times when manually racking the slide, the hammer would reach full cock, and then slip to half cock on slide return. I cleaned up the old lubricant where the sear faces the slide. I then re-lubed both surfaces. I haven't had a chance to shoot it yet, but manually cycling it leaves the hammer where it should be now.

I've actually been toying with the idea of getting a Cylinder and Slide matched hammer and sear set. I guess this gives me a good excuse to buy it.