Good Morning to everyone on the forum, This is my first post. Was hoping for some insight into replacing the mainspring housing and sear on my P938. Born date on the handgun is Feb 2015 and I have just started to see my hammer follow the slide home after a round is fired. After my tear down inspection I have found the detent on my mainspring housing wearing and allowing my mainspring to migrate up. I placed an order the other day with Sig for the new mainspring housing and updated sear spring but what I am not sure of is wether or not I need to also update my hammer to the Gen 3 design or if I can leave the original in the gun. Any thoughts or advice on this would be greatly appreciated. thank you to anyone who can advise.
Welcome to the forum.
I’m not familiar with the P938 at all, but if the gun is under warranty, that is something I’d let the factory fix to help ensure that everything that needed correcting was done properly.
“Most men … can seldom accept the simplest and most obvious truth if it … would oblige them to admit the falsity of conclusions … which they have woven, thread by thread, into the fabrics of their lives.”
— Leo Tolstoy
Call Sig on this one. If you are lucky they will pay the shipping both ways. Good luck.
The sear/ejector spring dimensions and MSH are the same as the old. The difference is in the manner the sear spring is fixed to the MSH using a 1/4 boss punched into the spring to engage a larger hole in the MSH to give it much more bearing surface than that little 1/8" plastic nub!
Your new spring/MSH should work fine with your existing hammer/sear.
Thank you to all who replied. A bit of an update, A conversation with Sig Cs confirmed that the hammer and strut in my P938 could remain the same when using the updated MS housing and sear spring. Installed the updated parts and headed to the range for a live fire test, with 50 rounds down range had 6 malfunctions of the hammer failing to reset after the slide cycled. Had to manually cock the hammer to fire the handgun. After a thorough inspection I can not determine why the hammer is failing to lock back and follows the slide home. Issue with the trigger bar?? maybe, I don't know. Have reinstalled the original MS housing and sear spring, wrote a detailed note to Sigs warranty dept, and will call Monday morning for return authorization. I hate sending firearms through the mail but in this case that looks likes the only acceptable rout. Will keep anyone updated if any are interested once I hear back from Sig. Any other similar experiences would be great to hear.
The reset function should not have anything to do with hammer follow, though the sear ejector spring moving up in the action can bung up all the works as you found.
Hammer follow can be caused by sear engagement angle - stock SIGs will normally have a positive sear engagement - (if you look at the side of the hammer while slowly pulling the trigger, you may see the hammer move back, cocking a bit further, before releasing due to the camming action of the sear coming out of the hammer notch), obviously, this positive angle, then, contributes to a heavier trigger pull, so changing the angle towards more neutral is often done during trigger work. If done improperly, and/or if sear spring tension is too low (or if factory parts are not fit properly) hammer follow can result.
Reset failure, on the other hand, is when after firing, releasing and again pulling the trigger does not cause the sear to release the hammer. In the P938, after firing and with the trigger still back, the trigger bar "hook" is under the sear. As the trigger is released, as the trigger bar hook moves far enough forward to clear the bottom of the sear, trigger return spring tension pushes upward on the trigger bar and this moves the trigger bar up into position against the front of the sear. To get there, the disconnector bar has to move up too, also powered by the trigger return spring (that's located inside the trigger).
All this stuff can be viewed with the left grip removed.
Thank you for the reply.Please forgive my wording in my post. Hammer reset was not what I should have said, rather hammer failing to cock after the slide cycled. Trust me, I am stumped, I've inspected all of the areas that you have pointed out and I still can not see any areas that should contribute to the hammer failing to lock into the fire position. Hammer notches and sear, plus trigger bar and hook all seem to be perfect without any unusual wear or obvious signs of nicks or burs. And all functions seem to work as designed. The pistol only began to do this after about the first 100 rounds went through the gun. Since then, about 15 failures. I was pretty detailed in my letter that will accompany the handgun to Sig. I expect they will be more familiar with this issue since I have read about it on more than a few occasions. One thing I did notice that I found odd. Under the slide where the bottom of the firing pin retainer cover meets the slide, there is some very pronounced galling, much more than I think I have ever seen on any 1911 styled pistol before. You can actually feel it as it pushes the hammer back and down when you manually operate the slide. I wonder if it is bad enough to actually bounce the hammer hard enough and fast enough under recoil to kick the sear out of the hammer notch allowing the hammer to follow the slide forward. Anyway, I can only guess that something is somehow not mating exactly or slightly out of spec. If you would like I'll update after Sig inspects and repairs the pistol. I am very curious though. I do need to fully be able to depend on this firearm.
I'd for sure be interested.
If you haven't already sent the gun in, there are a few additional things you might check. The first is to determine how much further than full cock does the slide depress the hammer. In other words, as the slide cocks the hammer and the sear clicks into position, the hammer should continue to be depressed slightly further beyond this point. With cun cocked, watch the hammer from the side as you pull the slide back over the hammer - this should slightly depress the hammer a small but visible amount.
Next test, slingshot the slide, pull it full back and release 15 to 20 times with your finger off the trigger. Can you get it to follow? Repeat while holding trigger full back - any follows?
Field strip, lower the hammer. Now look at the hammer and sear from the front of the frame. Pull the hammer slightly back and pull and release the trigger, the sear should move with the ejector and should go back solidly against the hammer as you release the trigger. As you cock the hammer, you can watch the sear click into the full cock notch. Pushing against the upper face of the sear with a punch or similar tool should not result in the sear moving further into engagement (in other words, the sear moves freely and fully into the full cock notch).
Good luck with this,
Well, all of the test you describe I was able to perform without any problems. Most of them I had already done, but went over everything again a number of times. What I did notice however is that when the sear engages the half cock notch, it seems to seat much deeper into the notch than it does in the full cock notch. It is however a very positive engagement. It does not disengage full cock unless I pull the trigger. no other manipulation seems to allow it to release. Now, I certainly do think that there is always the possibility that the sear angle or the full cock notch in the hammer could be out of spec slightly.
The more I looked at the pistol yesterday the more I think that there very well could be an issue between the galling under the slide and the hammer. Although I cannot get the hammer to fall by manually working the slide, I'm wondering if the force of recoil, combined with the speed of the slide when it returns forward, the galling striking the hammer and shocking it hard enough to actually kick the sear out of the full cock notch. there does actually seem to be enough play in between the hammer and hammer pin to allow this.
The pistol went out today back to Sig, so hopefully I will know more in a week or two. Most definitely will keep you posted. More than curious myself.
Please post back on what they find.
On the underside of the slide, just aft of the breach face and near that "bump" is where they do the Rockwell hardness test (a small center punch mark). At the aft end of the rail, the FP retention plate, I would think, gets the lion's share of force in cocking the hammer. I always put I light coat of grease on the rail with attention to the part the cocks the hammer.
Strange there would be galling there.
Agree there could be some anomaly in the sear/hammer engagement. As stock, the sear angle is positive (or should be) and when pulling the trigger and viewing the hammer from the side, the hammer will go back a tiny bit as the sear releases. This makes for a very secure sear/hammer engagement (while adding to trigger pull weight!). It also makes hammer follow less likely.
On a P938 trigger job, the sear angle is often reduced so it's not nearly as positive, and with not hammer follow - of course the parts are fitted nicely. All bets are off with the occasional MIM part that is out of spec and not hand fitted - and what you might be seeing. With SIG, they'll just say they replaced X we may never know for sure
Now this is what makes discussions like this so constructive.
When I originally noticed the heavy galling, my thoughts were directed at the hardness of the hammer vs the steel slide vs the firing pin retainer plate. For example, the retainer plate and the hammer show almost no wear, not even a polishing of the hammer face that you would normally see, yet the slide where it meets the retaining plate is pretty badly gouged. Almost as if the pin retaining plate is lifting ever so slightly as it pushes the hammer back, allowing the hammer to tear at the edge of the slide. Now, with all that being said it is interesting to note that this is a SAS custom shop P938. I wonder if it is possible that any additional machining that may be done on the slide could affect hardness even slightly, potentially causing the wear.
What I will say however, is the pistol is still quite impressive in such a small configuration. I've only been able to put about 200 to 250 rounds thru it up until this issue arrived, but I am still very comfortable with it. I really am hoping that after Sigs armorer reads my letter and inspects the firearm they can solve the issue. I know there are plenty of 938 owners who have never experienced any problems and are still running theirs.
Hoping for a very positive outcome.
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