Ruger Mk II Mainspring


March 31, 2003, 01:25 PM
I ordered one of these from On Target. Not sure how it installs. It looks like the "collar" that holds it to the shaft is installed and then the shaft is peened to lock it on?

Anybody know how to change these?

Anybody else use the On target reduced power spring?

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March 31, 2003, 07:41 PM
BH- Go to the MkII exploded view on the On Target web page. Which spring do you think you are replacing, the one labeled KA-57, or the on labeled KA20100?

March 31, 2003, 09:12 PM
The spring labeled KA01300 is the Recoil Spring Assembly, and I have never seen anyone replace just the spring. It usually is replaced as a complete assembly. The other spring is the Mainspring, that powers the hammer. It is fully enclosed in the mainspring housing, and it too, is seldom replaced(at least by me). To replace it, you must drift out 3 pins that hold the housing halves together. I haven't done it, I suppose it can be done or OT would not be selling them. Anybody else out there had any expirence in replacing these things?

March 31, 2003, 10:36 PM
bountyhunter, if you mean the mainspring, Ruger stakes the pins in the MSH. You have to drive the latch pin out. The mainspring comes out the bottom.

FWIW, I've only heard of two people who used the reduced power mainspring and both put the factory spring back in because of light strikes. I think Bill at Ontarget has a note on this on the order page.

My Mark2 with the Volq. accurizing kit installed has a 1.5# trigger with the factory mainspring.

Or did you mean the recoil spring?

Jim K
March 31, 2003, 11:10 PM
General comment:

The spring that provides power to fire the gun is always termed the mainspring, no matter what it looks like, where it fits, or if other springs are larger.

I think you mean the recoil spring, and you just remove the assembly that is on the bolt, and drop in the new assembly. They rarely have to be replaced, and then usually because one of the "legs" of the rear end has broken off.


April 1, 2003, 10:47 AM
Kruzr - Good call, you are right. Only the latch pin needs to come out. I suppose you could drive out the staked in pins, but I think you would have a real mess trying to get the MSH back into one solid, presentable package. My question, is removal of the mainspring part of what you would do for detailed stripping and cleaning? I have always just put a few drops of CLP down through the housing and called it a day. Would it be worth the trouble to disassemble and clean out the MSH? Does it tend to get a lot of crud in it?

Jim - That's why I asked BH to ID which spring he was looking at. OT has a picture of a spring with nothing else included. I have never seen the recoil spring replaced seperately, always as an assembly. And BH was talking about a rod through the center of the spring. It didn't jibe with what I was looking at. I was also under the mistaken impression that the MSH was a "sealed" unit, to be replaced with a complete new assembly. But that's why I hang around here, live and learn.

April 1, 2003, 01:08 PM
Sorry to sound confused, but I don't have the new springs yet and I was going by the description at the On Target website. I think they said the kit comes with a reduced power mainspring and RP trigger spring, stating that these will lighten triggerpull. I am new to "striker fired" guns so I am not real familiar with the names of the springs. I thought the mainspring was the long one on top of the bolt assy that rides on the little rod the delivers the firing strike. Reducing that generally does lighten the trigger pull some.

I am not necessarily going to install it, just bought it to try if it was easy to install.

April 1, 2003, 01:25 PM
BH- Got it! That top spring is the recoil spring (assembly). The Mk II is a blowback operated gun, and that spring is compressed at the end of the bolt movement toward the rear. It supplies the energy to strip the next round from the mag and return the bolt to battery. Let us know how fitting the new MS works out & if it is worth doing.

Porter Rockwell
April 1, 2003, 03:21 PM
Hello, be aware there is a detent ball behind the retaining pin that can launch into the Twilight Zone when released.
Honestly it aint worth the effort and as mentioned light striked/misfires are common with lighter than stock hammer/mainsprings

April 1, 2003, 03:22 PM
jrhines, I've never given much thought to cleaning out the mainspring housing. I don't think I'd take it apart though. Maybe blow some aerosol cleaner from the top to the bottom. My Mark2 probably has 15,000 rounds through it without cleaning the MSH or MS.

BTW, if you buy anything at Ontarget and have a question or need help installing it, Bill at Ontarget is happy to answer your question or give you a hand over the phone.

April 1, 2003, 03:35 PM
Thanks for the info. I studied the explosion drawing and now I understand it. I was confusing the recoil spring and the mainspring. I don't think I will change the mainspring.

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