Diagnosing feeding malfunctions in a SIG Ultra Compact 9mm

[Steve_in_Allentown]

Here are some insights on potential causes for the malfunctions shown in the pictures below. These malfunctions can happen to nearly any 1911 regardless of size and weight.

First, the pistol itself has a compact size, aluminum frame and very short barrel. These factors alone result in more muzzle flip and greater recoil impulse than heavier 1911s. This makes these small pistols more susceptible to malfunctions than their bigger brothers.

To help tame the greater muzzle flip and recoil impulse after-market flat bottom firing pin stops and heavier mainsprings are commonly added by shooters. Heavier recoil springs are counterproductive and are not recommended.




The first malfunction to address is a failure-to-extract. 9mm case rims are of noticeably smaller diameter than .45 rims. In addition, 9mm rim diameters vary from manufacturer to manufacturer. This makes fitting the extractor very important. There's not as much available leeway as with 10mm and .45 rims.

SAMMI specs for case rim diameters show there's only .026" available for the 9mm extractor to grab while there's .042" for the .40/10mm extractor to grab and .040" for the .45 extractor to snag.


Below we can see that the chambered round has been fired as evidenced by the firing pin hit on the primer. We can also see that the extractor made solid contact with the case bevel. Depending on how much force the nose of the extractor is exerting on the case bevel, it can result in the extractor not being able to snap fully down against the flat area between the rim and the bevel quickly enough to adequately engage the rim resulting in the extractor slipping off the rim and leaving the fired case partially extracted.

The fix is to relieve the front of the extractor to eliminate the contact with the case bevel. If the pistol has an internal extractor, more tension may help. If the pistol has an external extractor like this one does, replacing the extractor spring with a heavier one may help.

Personally, I would replace the SIG extractor and spring with those designed and manufactured by EGW.



Below is a live round stovepipe. I can't tell for certain but this round appears to have been the last round in the magazine. This particular stovepipe happens when the slide comes forward faster than the the magazine spring can push the next round up into firm contact with the feed lips. The slide makes contact with the case ahead of the rim and pushes the cartridge forward until it clears the magazine at which point the rim drops down, the nose pops up, and the cartridge is jammed up against the barrel.


Below is a close up of the stovepipe malfunction. Note the crease in the case where the slide hit it. The fix for live round stovepipes is a new / heavier magazine spring and/or a lighter recoil spring. Also, the inside of the magazine especially under the feed lips and the top of the follower should be bone dry.

Also, if there's a shock buff in the pistol, remove it. The reduced slide stroke can make the slide begin its forward movement sooner thus reducing the amount of time available to the mag spring to push the rounds up in time to be properly engaged by the slide.


Below is another live round stovepipe. Same basic cause as the live round stovepipe above just different timing.

[Bret]

Good pictures. I wouldn't bother wasting my efforts on fixing something that should run 100% out of the box. Send it back to the factory and let them sort it out. There's no excuse for unreliability. Send videos of the malfunctions because they're undeniable.

[Steve_in_Allentown]

Good pictures. I wouldn't bother wasting my efforts on fixing something that should run 100% out of the box. Send it back to the factory and let them sort it out. There's no excuse for unreliability. Send videos of the malfunctions because they're undeniable.

Good suggestions for folks who just want things to work without getting their hands dirty or learning anything new.

This is not my pistol.

Personally, I find satisfaction in correcting 1911 malfunctions, educating others, and building my own.

Perhaps you didn't pick up on the fact that I provided diagnostics and fixes for the problems in my post.

[Bret]

No. I picked up on it. It's just that the vast majority of people don't have such skills and even those that do shouldn't have to use them to fix a new factory-built firearm. The fixes that you detailed are not secrets. Why Sig or any other manufacturer would let a pistol out the door with such issues is beyond my understanding. Even though I might be able to fix such issues, I don't let them off the hook without first giving them multiple opportunities to resolve the issues. Plus, if your fixes don't work, you have to send the gun back to the factory anyway, and they find evidence of the attempted fixes, then they sometimes blame the owner. I once sent a USP40 back to H&K four times before they finally got it running 100%. I sent a Kimber 1911 back three times because it was having failures to eject. Based on how the spent cases were just barely making it out of the pistol, it was obviously over sprung. On the third trip back, I even told them how to fix it in the letter that I sent. They still didn't resolve the issues. Only then did I install a lighter mainspring. Not only did it resolve the reliability issues, but it lightened the trigger pull. I'll never buy another Kimber again, but I will buy an H&K because they owned the problem and ultimately fixed the pistol. All that said, I certainly appreciate the education provided by knowledgeable people such as yourself and enjoy building AR15's and AK's myself. I'm just passionate about making manufacturers own their design, manufacturing and quality control issues. Perhaps it's the industrial engineer in me. Sorry for sidetracking your post.

[Steve_in_Allentown]

I agree 100% on holding the manufacturer's feet to the fire. The only way they seem to learn is by spending their money on warranty repairs.