Slide not locking back on last round

[Stefan A]

It's a P365. I have 3 mags. The problem ONLY happens with the 10 round flush mag. Factory ammo. Happens with Fed HST or FMJ. I am not limp wristing and my thumb is not accidentally hitting the slide stop. After the slide doesn't lock back, I'll manually slide it back and it locks. But if I put the gun down on the table just a little too hard (which is to say how one would normally place down the gun), it will snap back. I suppose that could be the slide stop in that situation. But as I said, this problem is only happening with the one mag. Any advise?

 

[Ohen Cepel]

I'm guessing weak mag spring or something is binding it up. I would take it apart, look for burrs, etc. Clean it, maybe stretch the spring a little and try it again. If that doesn't work I think I would look about a new spring for that mag.

 

[mjsdwash]

sounds like what activates the slide stop is too short on that mag. Usually its a small bend on the follower. You can bend it back, or not worry about it. Seen it on a few 1911 and AR mags.

 

[herrwalther]

On every design that locks open, there is a tab on the magazine follower that pushes on the slide stop. Insert the empty mag and compare how far it comes up to a magazine that works. More than likely the mag spring is a little too weak but it could be caused by a damaged follower. They are pretty easy to fix on most magazines or you could just get a new 10 rounder.

https://lakelinellc.com/product-cat...rts-and-accessories/sig-sauer-magazine-parts/
https://gunmagwarehouse.com/sig-sauer-p365-micro-compact-9mm-10-round-magazine.html

 

[tactikel]

First clean your magazines, drop the base plate, pull the spring, follower and clean inside and out. Is your thumb “riding” the slide? Next clean and lightly lube the slide and slide rails ( with a light oil, not grease). Keep your grip high so the web of your thumb is tight. Replace your magazine springs. Have a friend shoot your gun to validate your problem. Change ammo ( if possible these days). Good shooting,

 

[gobsauce]

If it's the factory mag, send them an email. You might get a free mag.

 

[LiveLife]

It's a P365. I have 3 mags. The problem ONLY happens with the 10 round flush mag. Factory ammo. Happens with Fed HST or FMJ.

problem is only happening with the one mag. Any advise?

Contact customer service and tell them same exact thing and I won't be surprised if they replace the 10 round magazine.

 

[Stefan A]

Thanks everyone. It's been so frickn hot out I haven't even thought about going outside to shoot. So, I haven't thought about this is a week. But I will try to examine the magazine and then call Sig if that doesn't work.

 

[AK Hunter]

The spring in the one mag is weak. Try swapping springs to one of the other mags to see if it happens with that mag.

 

[jnichols2]

It sounds like a magazine problem, but let's look at everything.

The 10 round mags give you two fingers to support the pistol, but the 12 round mag gives you three.
That means the 12 round mag has 50% more support. On a very small pistol, that could easily cause limp wristing.

That's why I only carry with the 12 round mag.

 

[Rexster]

It's a P365. I have 3 mags. The problem ONLY happens with the 10 round flush mag. Factory ammo. Happens with Fed HST or FMJ. I am not limp wristing and my thumb is not accidentally hitting the slide stop. After the slide doesn't lock back, I'll manually slide it back and it locks. But if I put the gun down on the table just a little too hard (which is to say how one would normally place down the gun), it will snap back. I suppose that could be the slide stop in that situation. But as I said, this problem is only happening with the one mag. Any advise?

You may be experiencing a perfect storm of several combined causes. The slide stop and/or magazine follower could be slightly out of spec. The magazine spring could be slightly weak. Your grip may not be providing support, at the relevant places. Do not think in terms of “limp-wristing,” as a firm wrist is only one of several factors in supporting the weapon, during the recoil cycle. The middle, ring, and little fingers have a role in stabilizing the pistol, so, short-gripped pistols can be problematic for those of us with large hands.

 

[Stefan A]

That's all a very good point about the short grip with the 10 round mag. Only thing is, this never happened for my first several thousand rounds. Anyway, I really hope to get to this today.

 

[LiveLife]

this never happened for my first several thousand rounds.

That's how all firearm problems start out ... "Never happened before until now"

How many times have we heard:

• "Never had a failure to return to full battery until now" (recoil spring/ammunition issue ... apparently springs wear and are consumable )
• "Never had a failure to fire until now ... factory ammo" (hammer spring/dirty striker channel issue)
• "Never had a failure to extract until now" (dirty/extractor issue)
• "Never had a failure to eject until now" (ejector/slide speed/ammunition issue)
• "Never had a failure to feed until now" (magazine lips/follower/spring issue)
• "Never missed my target/POA until now" (operator input on trigger/grip)

So on and on ...

< Me > "Urrrggghhhh, this 22LR ammo is junk ... won't feed right" ... < cleans sand out of magazine > ... Wow, it now feeds wonderfully!

 

[Jim Watson]

I think that after "several thousand rounds" through a hideout gun with as many rounds as possible crammed in, that it might be time for a new magazine spring.

 

[LiveLife]

I think that after "several thousand rounds" through a hideout gun with as many rounds as possible crammed in, that it might be time for a new magazine spring.

 

[Stefan A]

That's how all firearm problems start out ... "Never happened before until now"

How many times have we heard:

• "Never had a failure to return to full battery until now" (recoil spring/ammunition issue ... apparently springs wear and are consumable )
• "Never had a failure to fire until now ... factory ammo" (hammer spring/dirty striker channel issue)
• "Never had a failure to extract until now" (dirty/extractor issue)
• "Never had a failure to eject until now" (ejector/slide speed/ammunition issue)
• "Never had a failure to feed until now" (magazine lips/follower/spring issue)
• "Never missed my target/POA until now" (operator input on trigger/grip)

So on and on ...

< Me > "Urrrggghhhh, this 22LR ammo is junk ... won't feed right" ... < cleans sand out of magazine > ... Wow, it now feeds wonderfully!

OK - so I was responding to the idea that my problem may be because of the grip and how many fingers I can get on it - which I think was pretty clear. Unlike all of your examples, the size of the grip doesn't change over time. It's a constant. Do you think I should clean my grip...? Maybe have my fingers thinned?

 

[LiveLife]

Do you think I should clean my grip...? Maybe have my fingers thinned?

Not at all.

There are shooting variables (And reloading variables if you reload).

If your pistol was reliable with the same ammunition for thousands of rounds then suddenly stopped being reliable, something(s) changed.

Identify all the shooting variables and one by one, rule them out and you will end up with variable that changed to make your pistol less reliable.

That was the point of my previous post.

Pistols are made with wear parts with some readily consumable (springs, etc.) and less readily consumable (barrels, etc.). If pistol goes from being reliable to not reliable, it is likely due to parts wear/breakage/maintenance issue if ammunition and shooter variable remained the same. That's why we have gunsmith/armorer and customer service and why I suggested you contact Sig customer service as your other magazines work fine.

It's a P365. I have 3 mags. The problem ONLY happens with the 10 round flush mag. Factory ammo. Happens with Fed HST or FMJ ... problem is only happening with the one mag. Any advise? ... never happened for my first several thousand rounds

Contact customer service and tell them same exact thing and I won't be surprised if they replace the 10 round magazine.

 

[CoalCrackerAl]

Some of my guns do it on a sometimes bases. I stopped letting it bother me. It was at random. It would happen maybe 1 in 20-30 mag fulls in different 1911's mostly.

 

[Stefan A]

Visually I could see no difference between the good and bad mag. So, I stretched the spring. It failed to lock back once out of 6-7 tries. So, I think that's an improvement. Thanks.

 

[sugarmaker]

Mag catch is actuated by a step in the plastic follower on the front left corner of the mag. Compare against a good mag, are they even? Is there crud (pine needle, burrr, built up residue after thousands of rounds, etc) preventing the follower from sliding all the way up? Did the mag ever get dropped and a feed lip slightly bent? Sounds like some marginal engagement, maybe worn plastic, maybe dirty.

 

[tarosean]

Only thing is, this never happened for my first several thousand rounds. Anyway, I really hope to get to this today.

Its likely time to start replacing all your springs.

 

[12Bravo20]

I have to agree with others, if it is just one magazine causing the problems, look at that magazine. Since it is used, clean the magazine really well and look at the spring and follower. And since you stated that stretching the spring helps, I would go ahead and replace it with a new one. I would still check the follower for damage or wear too.

 

[joneb]

It's a P365. I have 3 mags. The problem ONLY happens with the 10 round flush mag

I would consider the possibility your hold on the gun is different with the shorter mag and your thumb is in contact with the slide release.
I had this issue with Springfield 9mm XDS with the flush fit mags. but not the extended mags.

 

[LiveLife]

I would consider the possibility your hold on the gun is different with the shorter mag and your thumb is in contact with the slide release.

I was considering that until OP posted problem didn't start until after several thousand rounds as mentioned in post #12.

this never happened for my first several thousand rounds.

I am still suspecting the problem is magazine related.

 

[joneb]

I am still suspecting the problem is magazine related.

That would make sense if your carry mag. was the flush fit and more prone to spring fatigue because its always loaded.
I have a Sig 938 Legion with 7rnd mags. I load them with Six and I haven't had a problem, I've had the gun about 3 years and the mags. are always loaded.
This reminds me I should order new springs