Installed M-carbo trigger kit Kimber Micro 9 9mm

Tested my Kimber Micro 9 trigger pull before install with manual Wheeler gauge: 8 lbs+.

Installed M-carbo trigger kit, firing pin spring, new sear spring, hammer spring. Re-assembled
and tested action seemed fine; reset worked properly, cycled say 10 times no issues.

Tested trigger pull with manual Wheeler gauge 8 lbs +. Same as before. Put old parts in plastic bag as I removed them :slight_smile:

Has anyone ever experienced this and what was resolution?

Any guidance appreciated,

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when I got my Micro 9 Rapide, it had a 10 pound trigger pull. Sent it back to Kimber,they replaced the trigger assembly and cleaned up the sear and feed ramp. Brought it down to 8 pounds. I replaced the three springs with the MCARBO trigger kit, and it’s now 5.5 pounds…I wonder if any of those issues might be the cause.

Took the pistol out to the range two successive days. Had two FTFs on both occasions. Did two magazines on first day, and two FTFs on each magazine. Second day, same thing with different ammunition.
Symptoms seem to be light strikes on the primers on these FTFs. I’m debating putting the original hammer spring back in the pistol and seeing if that makes a difference.

FTF for me means “failure to feed”.
Did they fire the bullet? Then they are not light strikes.
I don’t know if that’s related to the trigger springs or to the recoil spring being to harsh. Did you shoot it with the original springs?
I did shoot mine a few 100s rounds with originals, just to get it to adjust.
Cycling it empty might help too.


Failure to fire. The pistol had no problems with the original springs, other than the extremely hard trigger weight. The primers that did not fire were very lightly dimpled, as opposed to the ones that did fire, which had pronounced dimples in them. The recoil spring is the factory spring, weight is 11 pounds for that spring, because the slide is a lighter slide than the standard Micro 9. I plan to take the hammer spring out and try it with the original spring and see if that makes a difference. It’s possible that the hammer spring is too light.

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That’s probably the case. It will increase the pull weight and probably it’s all you can do, short of selecting the ammo with softer primers.
To me, from all the brands that I had shoot, Federal ammo had the biggest indents in their primers.

replaced the hammer spring only. Five test pulls, 6.7 pounds (6 pounds, 11 ounces). Will take it to the range tomorrow morning and test it again.

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took to the range this morning. no light strikes on the primers, but did have 2 primers fail to fire. The trigger pull isn’t uncomfortable, so even though it’s not as light as before, with the original hammer spring in it, the firing pin has enough force to detonate the primer, so long as the primer is good. I’ll leave it like it is, although I might try a different brand of primer and see if that makes a difference with the two springs.


Maybe you already said, but did it ever fail to fire with all original parts?
What primers are you using?
You would have to go pretty light on a spring to get the light strikes/fail to fire you described
Possibly something is out of alignment enough that it is bleeding energy prior to strike.


No, it never failed to fire with the original parts. I’m using CCI Small Pistol primers. Several of my friends have said that CCI primers are somewhat hard…I have some Winchester primers I’m going to try.

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You didn’t say that you are using reloads with CCI primers.
Try Federal or Winchester factory bullets for a comparation.

when they become available.

They are known to be a little hard.
But other things you said, changing springs but not seeing a big difference in pull weight suggests binding or friction elsewhere.
+1 for Federal

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Federal has ammo on their website for a while now. Free shipping for larger orders.

I’m not sure you understood my earlier post - Kimber changed the trigger assembly and springs, and the pull weight went down to 8 pounds. When I installed the MCarbo spring set, the weight went down to 5.5 pounds, so that’s not a small difference. When I put the factory hammer spring in, the pull weight only rose 7 ounces or so, which with the stiffer spring, I’d have expected.
I’ll agree that the CCI primers are a little hard, but I don’t have any issues with them in my Taurus G2, or any of my other pistols.
SoNic, I’ll see about ordering some of the ammo from Federal. Thanks.

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Yea, I think I got your post and the OP mixed together. Hammer and striker springs can be lightened enough so CCI’s don’t work, but it’s not the norm.

Okay, now I’m confused…I bought a box of factory ammo (Blazer Brass), took it out to the range, fired 3 magazines through the pistol with no misfires, fail to feed, stovepipes, etc. Brought it home, changed back to the MCarbo hammer spring, out to the range again, 3 more magazines, no misfires, fail to feed, stovepipes, etc. One of my friends asked if maybe I’d mixed small rifle primers with the small pistol primers, but I always take only the primers I need and immediately put the packet back in their box in the cabinet before I start reloading. So, I don’t know…but I’m leaving the MCarbo spring in now. Trigger weight should be back down to 5.5 pounds, if not less. I’m figuring that the more I use it, the easier the trigger should get…


Who knows, maybe the primers were swapped at the factory? Did they seat correctly?
I don’t reload, so I don’t know if that’s possible.

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Good to hear.
Like to know if you have any of the cci primer loads left to try.

it’s possible, although I don’t know if small rifle primers will fit inside the primer pockets of handgun ammunition. I’ve got a ton of those reloads, and I don’t have any problems with my Taurus G2 shooting them. Well, I don’t plan to use the Micro 9 with anything but factory defensive ammunition.