I’m hesitant to ask for assistance because the gun has had a couple of minor mods done and they could very well be the issue. Basically there’s a few variables that I can’t check till I get my hands back on the gun.

Details... P320 Carry in .357Sig. Wilson Combat grip module, factory Sig straight trigger installed along with the Wilson Combat extended slide release/stop. Gun is near new, maybe 100rds through it.

Gun feeds/fires fine when manually running the slide, but attempting to drop the slide (on a loaded mag) with the slide release lever hangs it up every time. It just can’t get that first round into battery. Does this with multiple mags and it doesn’t matter if the mags are fully loaded or not. The slide goes home perfectly with an EMPTY mag while using the offending slide release.

Sorry, I know that’s a lot, trying to be detailed. I have ideas on things to try and have two other P320’s I can swap around slides, FCU’s, etc but won’t have my hands on it again till Monday. Any other thoughts or ideas are appreciated! Thanks guys.

Headed to sleep... I’ll check responses in the AM. Thanks!

My first thought, looking at the pictures, was that the mag didn't appear seated fully. The two possibilities there are that it's a compact mag (13 round) in a carry frame (14 round), in which case fully inserted wouldn't likely feed a cartridge at all. The other is that it's a magazine with the thicker dog ears (rounded, not beveled; round peg, not square peg in the base plate), or that doesn't have the dog ears removed, meaning the mag doesn't insert fully. Are either of those possible?

Long shot, I know.

The second, obvious choice is the magazine; correct magazine? .40.357 mag? Full size 14 round mag? No damage to feed lips?

The grip module shouldn't have an effect, unless the wrong base plates are on the mags or the wrong mags are in use. Likewise, the straight trigger has no impact, nor will the slide stop.

Using the same mag, does the slide lock back if the magazine is empty, when drawing the slide back by hand? If not, that's a sure bet that the mag isn't fully inserted (back to the wrong baseplate/dog-ear issue.

The same problem with a W/C extended slide release seems to have happened to this guy on his 1911. Not sure why that would happen. Maybe the release is dragging on the slide and reducing its momentum?

I would put the OEM slide release back in and retry.

Well I’m awake again..
thank you guys for the ideas. A little more info: mags are definitely 14rd Carry or Full magazines. Functions normally with an empty mag. I’m wondering if the buyer (fella that bought it) is loading the mags with 15rds? Edit: he said it happens with all 4 mags and loaded with various amounts (10rds etc.).

It’ll be interesting to pop that WC slide release out and try with the factory one.

I agree you should change back to the OEM release and see if it helps. But even before you do that, there's something else you could try.

Try activating the slide release lever extra fast somehow. See if the first round will chamber. My theory is that because of the long lever, the release isn't happening fast enough and the slide is hanging up just enough to inhibit round stripping.

Not a problem solver, but make sure the buyer knows that .357 Sig has very little bearing area for the bullet in the case, and less neck tension, and less capability to prevent setback, then other cartridges that more fully support the bullet from setting back into the case; a bullet that hangs on the feed ramp or that pitches up on the hood like that will likely get set back after one or two chamberings.

That bullet should be checked closely for overall cartridge length, and not put back in the magazine to be fed like that again. Depending on the cartridge, powder, and bullet, setback as little as .01 to .03 can raise pressures to nearly double, and for cartridges already close to their limit, that can be catastrophic.

Is this factory ammunition, or are these reloads?

With reloads, there are a lot of ideas floating around about how to do .357 Sig, and some of them don't help. Crimp, don't crimp, flare, don't flare, sizing. If it is reloads, is he resizing .40 cases, or using .357 Sig cases? What bullet profile?

The .357 Sig is sensitive to bullet profile. Some bullets curve toward the tip earlier than others, with less straight shank or body to the bullet, resulting in less bearing area in the neck, greater setback potential, and in some cases, a longer bullet...which may contribute to hanging on the feed ramp. The case in the last picture looks like a non-hollowpoint projectile in a case that has two concentric rows of markings; resizing die, perhaps?

My practice is to "slingshot" the slide to release when locked back, rather than rely on the slide lock lever. It's not inappropriate, per the manufacturer manual, to do it either way. The manufacturer does note that riding the slide forward can induce a stoppage, which may suggest that the aftermarket slide stop lever might be a contributing factor (if it's not holding the slide the same distance aft, for example).

The slide stop lever on the P320, while ambidextrous, does catch only on the left side of the slide. That does mean some flex and potential uneven movement of the lever, especially if pressed from the right. Whether that might contribute in some way, I don't know. On all my P320's (9mm, .40, .357 Sig, I have no problem chambering from slide lock by releasing the slide lock lever, or slingshotting the slide...but my preference is to take full advantage of the slide inertia, and the gross motor skill of simply wiping the slide aft, to release.

The pistol does have the FCU upgrades AND the upgraded slide?

Thanks a lot again for the info and suggestions. The ammo used were not reloads. Fiocchi I believe. The owner isn’t a newbie to firearms so I doubt he’s limp wristing it. It’s really annoying me. I wish I could get my hands on it sooner.

Just to throw a couple more variables out there, how clean are the feed ramp and the breechface? I've been harping on those two things for years, but not everyone always cleans those areas out carefully, and I've seen a good cleaning on those two places make a difference.

So I looked at my P320 and here is what I think is happening: when you activate the slide release it pushes inward, and where it pushes inward is right along the front of an inserted mag. So I believe that the WC extended release is contacting the magazine and putting pressure on it, which in turn pinches the top round causing enough friction to stop it from feeding. This would explain why the slide release works on an empty mag, and slingshotting works with a loaded round. So my first suggestion would be to change back to a factory slide release and see if that fixes the issue.

Good suggestion

quote:

Originally posted by Il Cattivo:
Just to throw a couple more variables out there, how clean are the feed ramp and the breechface? I've been harping on those two things for years, but not everyone always cleans those areas out carefully, and I've seen a good cleaning on those two places make a difference.

Very good, I appreciate it. Putting the Sig slide release back in will be the first thing I check off.

quote:

Originally posted by Puckpilot78:
So I looked at my P320 and here is what I think is happening: when you activate the slide release it pushes inward, and where it pushes inward is right along the front of an inserted mag. So I believe that the WC extended release is contacting the magazine and putting pressure on it, which in turn pinches the top round causing enough friction to stop it from feeding. This would explain why the slide release works on an empty mag, and slingshotting works with a loaded round. So my first suggestion would be to change back to a factory slide release and see if that fixes the issue.

Well I’m about 99% I’ve narrowed it down to the magazines. For some reason they are not playing nice with the Wilson Combat grip module. WC’s website says their modules are compatible with all “current XSeries” magazines.

Is there a third base pad I’m not aware of? There’s the original one with a round take down hole, the newer ones with a square take down...is there an XSeries on top of that that’s different??

No, just the two basepads, and what's critical is the shape of the dog ears. the simple solution if in doubt is to clip them off. Most of mine are clipped off, with many of my 17 round mags wearing Taran Tactical baseplates.

If the customer is using the older style baseplates with the thicker dog ears, then the mag isn't fully inserting.

A magazine may stay in place, under a little tension from the mag relese, but it won't be locked in place. It may sit just high enough to strip rounds from the mag some of the time, but probably not from slide lock. Looking down from above, when the slide is locked back, the mag appears to be in the well and seated, but it's not. This is also the case with a 15 round mag in the carry frame; it will insert but not lock, and appears to be correct. I've seen this happen in both cases.

The square peg mag will seat in the wilson carry frame. So will a round peg mag with the dog ears shaved, or removed. It's easier to just remove them.

--references above, 15 and 17 round mags, were to 9mm. As you're using .357 Sig, that would be 13, and 14 round magazines.

sns3guppy... well I’m glad to hear there’s only two base plates styles. Weird thing is the offending mags had the square take down hole.

I'm sitting here with a few P320's playing mag swap, and scratching my head, too.

Reference a previous thought regarding the extended mag release; I'm pressing the factory one into my Wilson frame, and it does press against the mag body, but a little below the feed lip, with no chance of contacting the cartridge. I can't imagine the Wilson part does any differently.

The thing is, the P320 mag sigs positioned almost in line with the chamber. Just a little below. So long as the magazine is seated, it's difficult for the round to not feed directly into the chamber, unless prevented by a previous cartridge (double feed, failure to extract, etc).

The failure to feed that your client is experiencing is perplexing. One possibilit that does occur is that he's bent the ejector. The ejector is integral to the fire control unit assembly. If a magazine is overinerted (eg, a larger length mag rammed into the frame while the slide is locked back, it can in some cases bypass the mag release, inert too far, and bend the ejector upward.

That might (?) make overinsertion easier next time, or might induce other malfunctions. If the ejector has been bent previously, it may apply upward pressure against the slide and cause it to contribute to an incorrect feed, though it's a bit of a stretch.

If the mags have been dropped at some point, causing greater curvature or tightening of the opening on the feed lips, that may also contribute.

The way the rounds look in the pictures, it just doesn't look like the mag is inserted fully. Maybe just the picture.

^^ Thank you very much for all your insight, it’s definitely been a help. He came buy this AM and I was able to fiddle with it. I was able to duplicate the malfunction. The WC release made no difference surprisingly. I was able to duplicate with the regular Sig mags that have a square take down hole. The two mags I had with Taran Tact. base pads worked fine. I’m stumped. I order him some new mags for the heck of it. He went to the range after leaving here and texted that it ran great (with the two Taran base plate mags.). I kept the others... I’m sure there’s something I’m overlooking.

Got pictures of the mags?

Has he had them apart? Springs correctly installed? No chance the springs are in reversed direction?

quote:

Originally posted by sns3guppy:
Got pictures of the mags?

Has he had them apart? Springs correctly installed? No chance the springs are in reversed direction?

I’ll photo them shortly.