Has anyone ever had an issue with their SW99 compact 40 failing to completely close the slide. I bought a used SW99 a month ago and have shot about 4 boxes of ammo through it and had no problems until the 3rd box when 2 cartridges appeared to jam (right in the middle of shooting qualifications for CC class). However, what was acutally happening was that the slide was not closing all the way shut. It was stopping about a 1/8" to a 1/4" from fully closed. Sometimes I can push the slide shut with not much force, other times it won't shut untill I pull the very tight slide back and eject the cartridge. I have cleaned the gun and can make it happen when I hand cycle the slide. It doesn't matter if I use JHP or FMJ, I can get it to lock up about 50% of the time. Anybody have any Idea what it might be?

No way to really know what's happening with a used gun unless you're able to handle and examine it in person. Can't diagnose things online.

However, in the interest of discussion, if the slide & barrel aren't closing into full battery when live ammunition is being used for live-fire (NOT "hand-cycling" the gun with live ammunition - that's what Dummy rounds are for) the following issues might be involved (one or more of them):

Condition and quality of ammunition. Examine the ammunition for defects and sizing/spec issues, and use new ammunition, if necessary.

The pistol might be dirty or too heavily greased/lubricated. Even if you've cleaned the gun, it mustn't be excessively greased or lubricated. It's amazing what can start to happen in the way of "problems" with overly lubricated pistols.

The magazine might not be within normal spec, or good operating condition, meaning it really might be a feeding problem that's interfering with the slide closing (when live ammunition is being used, as feeding/chambering "timing" is an important factor). The magazine ought to be clean and dry, with no damage to the lips. A weakened mag spring can cause feeding timing issues, too.

The Recoil Spring Assembly may be weakened (or weakening) and require replacement. Might be a problem with the dual spring recoil guide rod assembly. Yes, the springs can get tired. Damage or previously unidentified defects can occur sometimes, too. The recoil spring and the magazine springs are the first things I'd consider replacing in an older, used pistol, anyway. How do you really know their condition? Easier to start fresh. S&W recommends users of the P99/SW99's replace recoil spring assemblies & magazine springs in dedicated duty SW99's at 5 years of use or 5K rounds of shooting. FWIW, in the Gen3 and earlier Glock 22/23's they were recommending recoil spring assembly replacement as soon as 2,000-2,500 rounds (5K in G27's), although the Gen4's ought to be good for an estimated 5-7K rounds (as far as they're estimating for now).

All of this presumes no obvious problems that might otherwise exist. (Frame rails & locking block in good condition? Extractor have normal tension & freedom of movement? Any cracks, deformation or damage visible anywhere on the barrel? Signs of compression damage on the locking surfaces? Etc.)

At the risk of being overly obvious, if you're trying to hand-cycle live rounds to check the gun for a "problem" ... Don't. Not safe. Use Dummy rounds. Really. Aside from the risk of an unintended (negligent) discharge, repeatedly loading & rechambering the same rounds will risk damage to the cartridge (bullet setback, case rim damage, primer cup damage from shock, etc). Also, hand-cycling doesn't come close to how the slide runs under recoil, and feeding timing is different.

It's often amazing how variable "hand cycling" (for loading the chamber) can be when you hear it discussed and see it demonstrated by different folks, though. Pull back on the slide all the way and briskly release it to smartly run forward if loading. Don't "ease" it forward. Does it go into battery? It'll be even smoother under actual shooting conditions, when the slide is running under recoil & spring forces. I use the slide stop to release the slide and load the chamber most of the time, myself. (Long time 1911 shooter who finds the slide stop without having to think about it.)

Now, to field-check RSA's, Glock still uses their armorer test of pointing the EMPTY pistol upward at a 45 degree angle, with the trigger pulled, and slowly easing the slide forward (slowly, but not really slooooooowly). If it goes into battery the RSA is still serviceable. (BTW, this test will not be accurate with the Glock 10/45's, as their heavier slide mass can cause even brand new RSA's to "fail" the test in the 10/.45 guns.)

Any chance you can get the gunsmith at the store where you bought it to examine it? Any sort of a warranty offered by the dealer? Since you're not the original owner of the gun, technically S&W's lifetime warranty doesn't apply to it now that you own it (unless it was a "demo" gun, perhaps), but they've been known to err on the generous end of interpreting their warranty service. You might call and ask, explaining what the gun appears to be doing (and not doing), and see what they say.

Just some thoughts. If you lived close to me I'd offer to look at it. Sorry.

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Ret LE Firearms inst & armorer

you got it used. is it pretty fresh yet?

My XDm did that on occasion for a bit in the first few hundred. It comes from a slightly too tight chamber. the fact that is was just the one box and not the 2 before suggests it might have been a slightly oversized run in that box, or a dirty chamber.

That pretty much covers it! Thanks for that detailed response Fastbolt, I own the SW99c also. So If ever encounter this type of malfunction, I have an immediate reference.

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82nd Airborne Div 1980-1986

You're welcome, but remember that any particular gun will still require careful diagnosis if a problem is suspected. "Probable causes" are just that ... probable causes. Sometimes a problem may turn out to be more of a symptom of a different problem.

Also, different companies may have different recommendations about use/manipulations of their designs (such as using the slide top lever to release the slide and load the chamber, versus using the 'slingshot' method, which actually allows for a bit more slide travel and spring tension).

The Walther P99 series (and Walther licensed S&W's) are actually pretty reliable and good pistols. Walther America (importer, distributor & warranty service provider for Carl Walther in the US) only has a single repair technician on staff. Having spoken with him, it's not like he's over-burdened with making repairs, either.

Day in & day out, pistol stoppages and malfunctions are generally caused in some manner by the shooter (grip/manipulation, fatigue, maintenance practices, etc), followed by ammunition issues, followed lastly (and not nearly as often as some folks might suspect), actual gun problems.

Guns do experience normal wear & tear, though, meaning parts (like springs) do wear out at some point, and it's during the end of the service life, when they're starting to become weakened, that some erratic and puzzling things can seem to arise.

Dirty guns, whether dry or wet, don't seem to run as well as clean guns, either.

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Ret LE Firearms inst & armorer