Posted: 2/25/2026 9:39:40 AM EDT
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the MCX at Lejeune have a new shipment of the Sig M18 (TC serial numbers) pistols. Box’s show 2/3/2026 mfg dates. Any reason to think Sig may have tweaked the innards with updated parts since the massive PR fail over the 320? Thinking I need one of these. It would go well with the GI M17 slide I got a few months ago and had no real use for. Kind of a 2 in 1 gun. |
“You either know and understand history or you trust the government. You can’t do both”
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I have no idea but I do own many Sigs of all years and can say for sure they are constantly "Tweaking" parts. I think MFG's change parts all the time for various reasons. I've seen this many times, most recently with my P938 that has had a few different main spring versions (The last one finally works), mag release spring versions and even the mag catch design. I find you need to be careful when buying parts (Even Sig OEM parts), especially off of Ebay because you may be buying the previous generation and not realize it. Seriously, I just had this happen with the 938 mag release spring-the new spring is stiffer than the old and does a better job of not letting the mag drop during firing (A pretty common problem). so in a nutshell I would bet the latest version of the firearm has tweaks of some kind. Have they solved "THE PROBLEM" ???  Beats me. |
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I have both the M17 and M18 and like them both. As far as I know there has been no reports of a unintended discharge with these in the military. There is a report of an air force person but it was found that it was intentional and the person charged. I think the only potential concern with these perhaps if you plan to carry them loaded but otherwise as a range toy and just enjoying it, it seems to be okay to me. I had a M17 back in 2018 to about 2021 and never had a problem with it. I sold it but then decided to rebuy it earlier this year due to Virginia having an AWB. Overall I say get it as it is fun to shoot and the trigger is phenomenal out the box. I really like it and recommend it. |
| I looked at a black P320-M18 at Quantico today and thought it was odd that it had what I assume is a normal P320 serial number that started with something like “57K56…” instead of “M18A123…” like all the other commercial M18s I’ve seen up to this point. The serial number was also engraved with sort of an ugly dot matrix font. This is one of the new commercial pistols with the military style slide with the single bolt for the rear sight (so it can mount the Romeo-M17). Seems odd they’re no longer doing the “M18” serial numbers. Not sure if it has something to do with the black M18 being part of their professional product line, but I doubt it. |
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Originally Posted By ALASKANFIRE: What does that mean? What's the difference? There are some difference in the commercial SIG pistols and the actual ones that SIG makes for the military. Here’s an old discussion about the military production M18 pistols, which are only sold through SIG law enforcement dealers: What's up with these M18's? I posted comparison photos of the military and commercial slides on the second page here. |
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Originally Posted By 3ACR_Scout: I looked at a black P320-M18 at Quantico today and thought it was odd that it had what I assume is a normal P320 serial number that started with something like “57K56…” instead of “M18A123…” like all the other commercial M18s I’ve seen up to this point. The serial number was also engraved with sort of an ugly dot matrix font. This is one of the new commercial pistols with the military style slide with the single bolt for the rear sight (so it can mount the Romeo-M17). Seems odd they’re no longer doing the “M18” serial numbers. Not sure if it has something to do with the black M18 being part of their professional product line, but I doubt it. So, I got the M18 from the MCX (TC #) 2/3/2026 mfg. Also picked up a M17X from a LEO store (58K #) 12/4/2023 mfg, with a GI slide and M17 Romeo on it and in a X Frame. Going to part out the non-safety 58X FCU or sell it unused. Modified the XFrame to accept the M18 safety FCG. Using the M18 and M17 slides on the Modified X Frame with the TC# FCU. The M17 is more accurate and I do like the Romo M17 optic. As a long time Beretta owner the Sig slide “fit” is pretty sloppy with both slides on the frame. Smooth and zero issue, but loose left/right and up/down……as compared to most any Beretta. Probably a poor comparison sample though. |
“You either know and understand history or you trust the government. You can’t do both”
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Originally Posted By dalle0001: I have both the M17 and M18 and like them both. As far as I know there has been no reports of a unintended discharge with these in the military. There is a report of an air force person but it was found that it was intentional and the person charged. I think the only potential concern with these perhaps if you plan to carry them loaded but otherwise as a range toy and just enjoying it, it seems to be okay to me. I had a M17 back in 2018 to about 2021 and never had a problem with it. I sold it but then decided to rebuy it earlier this year due to Virginia having an AWB. Overall I say get it as it is fun to shoot and the trigger is phenomenal out the box. I really like it and recommend it. Japanese contract guard on US Marine post, safety on: https://www.ar15.com/forums/handguns/Master-P320-index-thread-NO-opinions-allowed-post-links-and-data-only/14-216492/?#i2554655 OP, IIUC, your sear engagement is negatively affected by a loose slide to frame fit. Godspeed. |
I sell firearms produced by the finest child labor in the world, be it Filipino, Muslim, Mormon, Arizonan, or Texan.
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Originally Posted By backbencher: Japanese contract guard on US Marine post, safety on: https://www.ar15.com/forums/handguns/Master-P320-index-thread-NO-opinions-allowed-post-links-and-data-only/14-216492/?#i2554655 OP, IIUC, your sear engagement is negatively affected by a loose slide to frame fit. Godspeed. Yea, figured as much. No loaded carry with it till they sort this out. Nice feel though. |
“You either know and understand history or you trust the government. You can’t do both”
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Originally Posted By backbencher: Japanese contract guard on US Marine post, safety on: https://www.ar15.com/forums/handguns/Master-P320-index-thread-NO-opinions-allowed-post-links-and-data-only/14-216492/?#i2554655 OP, IIUC, your sear engagement is negatively affected by a loose slide to frame fit. Godspeed. As far as I understand it, even as that post mentions that the AF person was goofing around. I remember reading some other articles about how he eventually confessed and got charged for it. But I don't know if they rescinded the standing order not to carry it loaded. I actually go to the military base nearly daily, and have asked a guard there after reading that report about if they carry the pistol loaded with a round in the chamber, and he said yes. These are Navy security though. |
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I want to add in some other things about my post. To me, I feel most of the complaints involved has to do with something else. Most of the problems seem to be when it is inside a holster, so it appears something is off about that. I have yet to hear of a report where it goes off just sitting on a table or such. With that said, most of these cases involve LE or military persons. They are protected in terms of being sued or arrested because these are duty weapons that they are trained and used to that is given to them by the authority they work under. But as a citizen, if your gun goes off, there is no legal protection and even if the gun was proven to be defective somehow, you'll still be sued or face criminal charges. So it is best to always err on the side of caution. It should also be noted that SIG to this day has not really explained WHY or HOW these guns go off seemingly on their own but at the same time, I do not trust these youtube backyard gunsmiths as being some sort of technical experts on "tolerance stacking" which seems to be the buzz word to explain this. I think until a proper authority can explain how it is failing, then really everyone should err on the side of caution. |
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Originally Posted By dalle0001: As far as I understand it, even as that post mentions that the AF person was goofing around. I remember reading some other articles about how he eventually confessed and got charged for it. But I don't know if they rescinded the standing order not to carry it loaded. https://www.airandspaceforces.com/airmen-covered-up-facts-of-fatal-m18-shooting/ The Airman killed himself two months after being charged. |
Your self destruction doesn't hurt them.
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Originally Posted By scottrh2: Yea, figured as much. No loaded carry with it till they sort this out. Nice feel though. Originally Posted By scottrh2: Originally Posted By backbencher: Japanese contract guard on US Marine post, safety on: https://www.ar15.com/forums/handguns/Master-P320-index-thread-NO-opinions-allowed-post-links-and-data-only/14-216492/?#i2554655 OP, IIUC, your sear engagement is negatively affected by a loose slide to frame fit. Godspeed. Yea, figured as much. No loaded carry with it till they sort this out. Nice feel though. So one my sample of 2 (M17 & M18) I have noticed the following. 1) magazine out = more looseness to the slide/frame fit. Produces noticeable slide up/down movement when pulling the trigger. 2) magazine in = increased snugness of frame/ slide fit. With magazine in there is no noticeable slide up/down movement when pulling the trigger. 3) either way on both of my guns the contact area of the sear and striker remain the same as the sear pushes upward by spring pressure filling any potential gap that could be created by a fixed position sear and the slop in the slide; thus the striker looks to remain in maximum sear contact either with or without a magazine in the weapon. 4) observing sear movement while depressing the trigger even the slightest does move the sear downward. Once released without dry firing, the sear does pop back up and full contact with the striker is returned. I was surprised by how little trigger movement is needed to reduce the sear contact. “Taking up slack” is not a good idea with the 320 design unless fully committed to firing. 5) I have no real opinion one way or the other on the manual safeties my guns have. I do note that when in the “on” position they do block any trigger pulling thus no moving the sear; so I think that is a good thing. 6) Lights. I only put a light on when I need it, so holstering with a light is not something I do with these pistols. 7) I am only using snug fitting Safariland GLS (non light) holsters and a Bianchi M12 GI M9 holster. Neither of these allow any real slop or movement of the pistol while holstered. I could see that a holster that allows for a fitted light could allow the weapon to move around more due to the design limits. Summery;I like these guns. Yea, they are made to be cheaper to the maker by using stamped and MIM parts more than I really care for but they shoot good and are pretty simple unless you take the FCG apart. Due to size I not interested in CCW with either one. That said when walking or hiking I do feel safe with one up the spout and the safety engaged. No manual safety blocking the trigger movement?? ..yea I might change my mind on this one. No problem with one up the spout and a GLock, but the “accidents” do cause me to wonder just WTF is going on with the LEO 320s. |
“You either know and understand history or you trust the government. You can’t do both”
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It's interesting, I've seen comments about very loose slides on P320s a number of times, but that's never been my experience. However, when examining mine today, there's a noticeable difference between my commercial and military production pistols. My commercial pistols - a P320-M17 and several P320-M18s - have a very small amount of play side-to-side, and when I squeeze the front end of the slide (index finger on top, thumb under the dust cover of the grip module), the slide will "click" a little at the rear as the pressure pulls the front end down and the rear of the slide raises. My P320-M17 has over 3,000 rounds through it. The others have about 1,500 each, but the movement seems to be the same on all of them. I could see that causing concern with the possibility of the sear and striker separating enough to allow the striker to release, but I wouldn't say mine have that much play in them. I understand the concern about debris getting in there though. My military production pistols - an M17 and two M18s - don't exhibit any of that movement at all, either with or without a magazine inserted. Their slides sit very tight on the FCU rails and don't move sideways or tilt at all when squeeze at the front like my commercial pistols. They seem to have much tighter tolerances, possibly due to the pre-tensioned barrel's tight interface with the slide, which is certainly a much tighter fit than commercial barrels. Not sure, but it seems like the slide to FCU rail fit has no wiggle room. There's a very slight movement in my M17, almost imperceptible, but it's actually the FCU moving laterally in the grip module. The slide and FCU are locked tight together with no movement. Comparing them to other brands, I'd say they have the same or less movement than my Glocks. The only pistol I have that seems like a tighter fit is my HK USPc. It's interesting to see the difference between the two types of pistols. |