M*CARBO Brotherhood

P938 and MCARBO Trigger Kit and Polishing KIt

I purchased the MCARBO P938 Trigger Kit and Polishing Kit some time ago but had to wait till now to use, as it took months for my Sig P938 Legion to be delivered.

In the instructional video (outstanding resource) Patrick had a P938 from back when they were still being delivered with reasonable triggers. Approximately speaking, in the video he had a roughly 5 lb trigger which came down to a much smoother 3.5 lb trigger.

Well these days Sig is delivering triggers of 7 or 8 lbs and many people are reporting even over 10 lb so it’s a good question, what about the kit on current deliberately-crapped-up-trigger Sigs?

I didn’t measure my starting trigger pull but it had to be 9+ lb. It was also somewhat gritty and quite unenjoyable. I put 100 rounds through it as delivered (zero malfunctions, good on Sig there) and was overall very pleased with it, except for the poor trigger and the ABSURDLY difficult to move safety. The poor trigger still didn’t in any way stop delivering a full mag pretty quickly at 7 yards with all hits good from the standpoint of self-defense, but still, not good.

While the gun is obviously not for bullseye competition or anything like that, still part of my range experience is getting in some nice precision-focused shooting as well as getting speed by being only as accurate as needed. I felt the trigger was costing me an inch or a bit more at a mere 7 yards when being slow and precise. Impossible to say how much more it might have been costing when going as fast as possible. Several inches seems quite plausible. Anyhow that’s where the gun was at.

I only gave 10 minutes polishing to the hammer. It may be that my Dremel, which is a 1 speed, turns faster than the lower setting of Chris’s Dremel. In any case, at 10 minutes I thought it done.

On performing the spring replacements, what an improvement.

I haven’t measured it yet, but I would say 7-8 lb, and – judging relative to handguns in general not competition 1911’s or CZ’s – it’s good quality now. Very pleased with feel. It really doesn’t need more work. A person could well think for carry use one ought to stop right there, and one certainly could.

(Edit: Measured at 8 lb. Both my wife and I find it almost unbelievable that 8 lb feels this good. For anyone reading, if that number sounds like a turnoff, please let me be clear the trigger feels WAY better and I have no doubt it will make a real difference in shooting. Smooth quality vs gritty, clean, definite, and changing in category from “just too heavy” to “absolutely can work with this.”)

My thoughts are that sear spring adjustment might bring it down to the 3.5 - 4.5 lb I’d prefer, but I will have a gunsmith look at that rather than attempt myself. I also wonder if part of Sig’s deliberate heavying-up program may not have included an over-heavy firing pin lock spring, so I plan on getting a Mustang spring and when I bring it to him if my gunsmith considers that worth doing, that’ll be on the table. If not, I’ll be out $4 or so.

Lastly, thought I’d mention that the absurdly-stiff safety problem was completely solved by swapping out the safety detent spring with a Mustang part. The Sig spring puts absolutely insane pressure on the detent. I suppose the purpose was so ladies can toss the 938 into their purses and rummage about without fear of the safety lever moving. That sort of thing is probably is why they heavied up the trigger as well. (At least Rock Island cited non-holster carry as to why they heavied up their Baby Rock trigger, delivered to me at 13 1/4 lb. Not a good gun overall, not worth even its low price. In contrast the Sig is worth the money IMO.)

Will report back after the gunsmith work or evaluation.


I went to get the P238/P938 trigger kit, but I didn’t know if I had a Gen 1 or Gen 2. How can I tell which generation I have?

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Very broadly, and not wanting to be too obvious but just sharing all I am sure of, ones from the last few years are Gen II and earlier ones up through at least 2011 are Gen 1.

Because my wife has a P238 HD from 2011 I websearched to find the approximate year cutoff and hers was solidly in the Gen 1 range but I don’t recall any better.

There is also a physical examination that will determine it.

And while it wouldn’t prove it, a trigger pull below 7 lb would at least strongly indicate Gen 1.

As an update on my thread: I bought my kit before the upgrade which now accounts for the Gen II’s having heavy sear springs. I did not wind up getting my gunsmith to adjust my existing spring as he did not want to do it.

It is great news MCARBO now has the lighter sear spring and I am going to go with that.

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Gen II kit on its way!

So now we will see what happens with the sear spring is replaced as well, with the MCARBO.

As good as the trigger quality-wise with just the earlier steps, I think this is going to turn out great.

And as an extra bonus, the duplicates that I’ll be getting of the mainspring and firing pin spring due to having first bought the original kit and now the Gen II will not go to waste, as they are all that’s needed for my wife’s Gen 1 P238. So it still winds up two kits purchased, two guns upgraded. Besides that my Polishing Kit now gets double duty! :slight_smile:

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I installed the trigger kit on my P938 Sport13. It dropped the trigger pull to about 4-4.5 lbs, half of what it was. I also added the Grayguns trigger. The change in trigger geometry also helped and eliminated the pinching of the trigger finger many get from the stock trigger. The picture shows mine with the new trigger installed with the stock trigger along side. I still need to address that safety issue, way to much pressure needed to function it. A little Hornady One Shot dry lube helped a bit, but not enough. You referred to solving it with a Mustang part. Would that be a detent spring for a Colt Mustang?

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It is an interesting concern for me. My hold drops the safety on the draw and my strong hand thumb rides it until it is reholstered.

I have experienced the opposite problem several times. I’d probably still have my M&P 2.0 if I hadn’t continued to find it brushed off ready to fire in my holster. I actually swapped in a heavier spring trying to stiffen it but that was a fail. Less problem with a hammer and without an ambi safety.

I actually have a parts collection in my to do box to work my 938 trigger and get rid of the ambi on the safety. They are awesome little pistols.

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“You referred to solving it with a Mustang part. Would that be a detent spring for a Colt Mustang?”

Exactly. Drop-in, and a world of difference. I expect it is essentially identical to or the exact same as the earlier Sig part, before they decided to make it “safer” to carry loose in a pocket or purse, or whatever their reason was for turning the safety and trigger so stiff.

Btw I have bought a Cylinder & Slide single sided extended safety, which seems a very nice part and when temporarily on the gun was exactly the size and shape I thought perfect for the gun, but it turns out one cannot just drop a single sided safety in place of the ambidextrous, regardless that it looks like it fits. A different hammer pin is needed, apparently a P238 part if you try to do it yourself instead of asking Sig to do it. I have that on order: we’ll see how it goes. Also, in some cases the C&S is not drop-in anyway, according to them. So again, we’ll see how that goes.

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Are those springs the same for the P238 and the P938

Yes. Indeedy. Quite so.

(had to get to 20 characters)

Well, I finally got to put the sear spring and retainer from the Gen 2 kit into my new P938 Legion that had already had the hammer and firing pin springs from the original (same as Gen 1) kit, and the extra hammer and firing pin springs into mw wife’s used P238 HD.

Total success, absolutely what I was envisioning for the Legion. It measured 4 3/4 lb which may not sound super but it was crisp, clean, no mush, really precise wall and exact feeling break. It felt lighter than it measured.

It had been just over 8 lb before the sear spring change.

The P238 dropped from 5 3/4 to 3 3/4 lb with the Gen 1 spring changes and a quick hammer polish. Quality wise it wasn’t as good as the Legion but wasn’t by any means bad at all. My wife was very happy with it. The quality difference is from the hard parts in the gun I’m sure.

My Cylinder & Slide extended safety still doesn’t work even after getting the 238 hammer pin. I should have known better, years ago that outfit utterly ripped me out of a little over $200, so I guess that one’s on me.

I totally recommend the MCARBO kit.