Home Forums Hunting & Shooting Handguns Sig P938 .22 Conversion Unit: The Good, The Bad And The Ugly

I was the first kid on my block with a Sig P938 .22 conversion unit. Sig makes two kinds of conversion units. One is the same size as the standard 9mm upper. That version has a full length guide rod and a 3.3� barrel. I think it was originally intended to have night sights, but Sig�s website is ambiguous and I do not know the reality. The other is a long slide target model with a 4.1 inch barrel. (Sig rep said 4.4� in SHOT Show trailer but NRA print version says 4.1�.) It looks more like a traditional 1911 slide with a barrel bushing. It has adjustable target sights without any tritium inserts.

I bought the target model off the Sig website in early August for $302 shipped. A couple of days later I checked the website and saw it listed for $352. I guess I got �lucky�. The website says that the other version sells for $302 shipped.

I bought the target model because I view the conversion unit as an adjunct to the 9mm gun and not a substitute. It also lessens the possibility of getting confused and finding that I have the wrong upper on the gun. The downside is that it will not fit in a pocket that accommodates the 9mm version of the gun.

The unit came in a small plastic carrying case. The upper was well oiled, although I did run some patches down the barrel and lube the slide and frame with TW25B before installing. The kit comes with one plastic magazine with a finger extension allegedly rated for 10 rounds. The ejector is on an extension affixed to the barrel assembly. The upper slipped onto the gun very easily. (Remember to depress the 9mm ejector when installing the slide.)



The sights are nice. There is a high profile front sight that feels like aluminum. It has a large white dot. The rear sight feels plastic and it has 2 white dots that are smaller than the front sight dot. The rear sight gap is narrow and the front sight takes up almost all of the gap, which is good for precise shooting. The rear sight has one large screw, which I think is for elevation, and one small screw, which I think is for windage. The instructions offer no guidance on this, or which way to turn to affect POI.

One major quirk is the fact that the magazine does not actuate the slide stop and lock the slide back on the last shot in the traditional manner. Rather, the slide stops by friction, hitting the rear of the magazine follower and stopping before engaging the slide stop. This creates a couple of unique conditions. First, the magazine will not drop free when you depress the magazine release button. Second, if you try to strip the magazine or pull the slide back enough to free the magazine and then release the magazine using the button, the slide will slam forward on an empty chamber if you do not hold it back. Only by pulling the slide rearward and engaging the slide stop will the slide lock back in the traditional manner. I can live with this for a conversion unit, but I think I would be upset if I spent $600 on a dedicated .22 LR gun and had that issue. I do not know if this issue is unique to conversion units, and/or whether it is unique to both of the two types of conversion units. I suspect that the magazines are all the same, though, and they do not appear to have the indentation in the front of the follower that traditionally activates the slide stop.

The instructions, which are very limited, say that the gun is intended for high velocity ammunition and that standard velocity ammunition may give some functioning problems. I was disappointed by this. Luckily, I had some CCI Velocitors and Stingers on the shelf, but I was hoping to see how it did with bulk pack.

I only got a chance to shoot about 70 rounds the first morning, back in August. The plastic magazine is the easiest .22 LR handgun magazine I ever have loaded. It is a bit harder getting the 10th round into the magazine, and it changes the orientation of the cartridge. The cartridges appear to be staggered in the magazine, although not nearly as pronounced as with a Ruger SR22.



I shot the first magazine loaded with Velocitors. The first round fed from slidelock and fired fine. The second round jammed on the ramp. I got the same issue with Stingers, and with another magazine of Velocitors. I decided this is a 9 round magazine, at least with these rounds and before being broken in. Aside from this issue, I had no malfunctions with Velocitors or Stingers. The Velocitors were hitting to the left of my point of aim, and the Stingers were still left but closer to center. I have since learned that Stingers and Velocitors are frequently referred to as �hyper velocity� rounds rather than �high velocity� rounds, so maybe they are just too fast for the gun.

I tried some Federal bulk pack. I did have some failures to strip a new cartridge. The slide would close on an empty chamber. I could tell they were not moving the slide as authoritatively as the high velocity rounds. On the other hand, when they actually chambered they were more functional than they have been with some other .22 pistols. I had no misfires, which happens regularly with some other pistols. I think the fact that the 938 has a hammer and a bit of hammer travel is the reason for that.

Once I got the sights figured out, I was hitting a small Gatorade bottle at 25 yards with regularity. I did have one magazine with the bulk pack that gave me a lot of trouble. I am thinking that the gun will smooth out and do better as the slide and recoil spring break in.

The next day I went out and shot another 80 rounds of Velocitors and CCI JHP Mini-Mags. The Mini-Mags are �high velocity� rounds but not hyper velocity rounds. In some instances, loading from slide lock sent the first round flying out of the gun and not chambering a round. I also experienced the same thing during strings of fire. A round would end up on the ground and the gun would have an empty chamber. I also had some instances where the cartridge flipped me off by sticking straight up, caught between the slide and the barrel. I was offended but maintained my composure.



After two days I was ready to sell it on the Internet for half price, with full disclosure. I was really mad. My wife, who is pretty bright except for marrying me, suggested that I at least give Sig a chance to make it right. In anticipation of sending the unit off for evaluation, I cleaned it and hosed it down good with Break Free.

I never sent the gun to Sig. Instead, this afternoon I decided to give it another shot with some more CCI JHP Mini-Mags. (I ramped up acquisition of these in the last couple of months due to my willingness to pay more than 8 cents a round, to the chagrin of many on the Rimfire Forum.) The prairie was beautiful and the gun�s Karma was pretty much in synch. The bulk pack still won�t feed reliably. I had one instance, after loading the magazine with 10 Mini-Mags and using the slide release, where the first round went flying out the gun and the chamber was empty. But, the rest of the Mini-Mags functioned great, and the sights and functioning were great. I had no problems when loading the magazine with 9 rounds of Mini-Mag.

So, as a 9 round gun with CCI Mini-Mags, it works well. I will dial in the sights for that. I sometimes throw the P938 in my emergency kit as a backup gun, and the upper will fit in there as an additional bit of utility.

So, is this unit really worth the current price? Not really, unless you have a specific niche for it. You can buy a Ruger 22/45 for less! Is it worth more than half of what I paid for it? Yes, but probably not by much. YMMV

Pretty detailed review and sorry it didn't rise higher in your opinion than it did.

I have a P226 with Crimson Trace grips and bought the 22 conversion kit for it. I have an assortment of high velocity 22s and found in shooting over bags with various brands at ten yards against a Colt Huntsman, a Ruger 22/45 with a Trijicon site, and a S&W Airweight that it is my most accurate 22.

The caveat is the Crimson Trace might be the ringer among the other sights.

No hiccups with magazines or feeding and ejecting either. Mine was around $325 IIRC and was worth it to me. The P226 gives you a handfull of platform for shooting a 22.

Sounded like a good idea when they announced its release. But you just saved me from spending $350 on one. Thanks for the honest review. I'll just stick with my Ruger SR-22 when I want to pack a lite, small .22 autoloader.

Obviously the CCI Mini mags are the problem....you can dispose of them at my house

Those are the only ones that work well with this unit, but I can spare some if you need them.

great review

the more of your posts I see the more I'm convinced you're a squared away citizen

Just joshin ya...you need a good revolver though

sr22 won't fit in your pocket. the Sig 22 does (if you are smart enough to get the short barreled version, that is). It's never a good idea to practice firing 9 shots out of a 6-rd gun (ie, the 9mm that you are training to use). So the mag hold-back being lacking is not a big deal. If they used the usual 1911 type slide lock, the aluminum slide would be chewed useless (in the slide lock notch) in 100 mags full, anyway, if you let it lock open. So Sig just avoided the issue. can't use a steel slide of this size and weight, unless you use the "floating chamber" of the old Colt 1911 22 unit, of which half of the barrels had to be replaced, because Colt was just no capable of machining them to close enough tolerances. those barrels cost upwards of $300 today, so aluminum slides are what everyone uses, except on little bitty things like the Beretta M21

try some federal or superx "solids" If you insist upon using hps for mere practice, try building up the follower's top with jb weld expoxy, then shape it with the dremel, leavig the follower "build up" by about 1/16". it will help with feeding the hp's.

threading the 4" barrel for a silencer, with the 3.3" slide, makes for a really sweet trail gun. There's a way to have a very quiet silencer, which is just 2.5" long. You have to make it 1 1/4" in od, with a 7/8" interior tube. the rear 1" of the 7/8" tube has lateral vent holes, into the "sleeve area" betweeen the tubes. There also has to be an "underchamber", making the can look a bit like an O/U double barrel shotgun, to get enough volumetric capability. To get it super quiet, it has to be run "wet", with water in it. But it's pretty quiet when dry. Running it wet is worth 3db, normally, which is a doubling of the audible sound.

I believe that your keyboard (or touch screen) needs a generous application of J-B Weld and a Dremel tool more than my magazine follower does.

hey, if you're the type that would rather clear malfunctions than have a gun that works, go for it. Far be it from me to stop your being stupid.

Obviously you have no clue.....

Cheyenne,

Nice review, glad to hear you kinda made it all work out. In my experience, CCI Mini Mag's are almost always accurate and reliable in most any gun. They're one of the best made rounds out there, just consistent as all get out. Mini Mags are rarely THE most accurate round in my .22's, but it's the one round I can buy for all of them and will shoot nearly as good as THE most accurate round, but do it across a wide selection of guns, both rifle and handgun.

The hold open thing is pretty much part for the course on a rimfire conversion unit.

If .22 ammo ever gets reasonable again, a 9mm/.22lr Sig 938 would be a nice combination.

Thanks. I put another 80 Mini-Mags through it tonight and it functioned perfectly. I even tried it with the 10th round in the magazine s couple of times and it worked from slide lock. However, I am questioning whether the "target" version was the way to go. The unmodified trigger is so stiff and variable that true target accuracy is a bit difficult to achieve. Without a rest and a good amount of time, a squirrel would be pretty safe from me past about 7 yards. It should work for shooting steel, though.

When I finished with the Mini-Mags I grabbed a handful of bulk pack and thought about loading some in the magazine. Then I decided not to press my luck. Maybe in a few thousand rounds.