Went the range today. My HK VP9 was failing to go to slide lock on the last rnd maybe 50% of the time. I tried new and older mags, and same deal. Gun has approx 1k rnds on it, so I wouldn’t expect a spring replacement required yet. What does the M4C brain trust recommend I do for diagnosis and fix? It’s been dead reliable to this point.
When that happens to me I am accidentally riding the slide lever. Even when I think I am not.
That is my guess, as well.
Possible to be sure, but I have been working with this gun for a while now without that issue. What I’ll do next time is pay special attention to that and see what happens.
Thanx.
-Inspect the slide stop and notch for peening or deformation?
-Could it be cheap/weak ammo at fault? Does recoil seem consistent and sufficiently strong? Try hotter ammo?
-Compare all your mags with one another and ensure the followers are all matching height, angle, etc.
-If you’ve detail stripped the gun lately, make sure you reassembled the slide stop properly. This same problem occurred with one of my Glocks when I accidentally put the slide stop spring OVER the pin, rather than under it.
-A long shot, but maybe carbon buildup somewhere weird could be causing the issue?
What ammo were you shooting? Was it cheap, under-powered range fodder?
I started having it BAD with my old Hk45. I noticed when I started shooting steel and timing myself the issue became more pronounced. Glocks are always biting me in the butt under speed (except they usually locked open early). And like you, the issue wasn’t consistent. It would just creep up one day when I wasn’t being careful (especially if I let my support hand separate from the grip and push forward.) If it is still happening, always try one handed and see if it pops up. If it is till happening one handed it is time to call the Krauts.
This is one of the things I like about designs like the M&P and FN that have their slide releases well shrouded. Sure it is shooter error, but I like a gun to be as Greg proof as possible.
This.
A detail strip may be in order. Will, you weren’t limp whisting that 15th round were you? 
This still happens to me some times with mine…the position of the slide stop is the only thing I don’t like on the VP’s. I went to large panels all around and it helped. It’s hard to remember to keep my thumb positioned to not hold the slide lock down sometimes.
Loading one or two in each mag and doing slide lock mag change drills helped me work through this issue.
As others have said, I think you are riding the slide release. If you can, try a larger sized backstrap to put more distance between your finger and the slide release.
Riding the slide release is the most likely issue. I have a P30 that I have put close to 20k on and every once in awhile under high stress I will ride the release.
I put 2k on my VP9 and had it happen a couple of times before I sold it.
The VP9/P30 are both a little touchy on this issue. HK has a short release available for the P30 that clears up its issue and ome will come for the VP9 as well.
Glock got that one right IMO.
Inspected. I didn’t see anything.
Mags look consistent
Never detail stripped to date
Was using cheap PMC range ammo, so tried a few mags of hotter CCW ammo also.
Yes, but also tried some quality hot stuff to see if that was the issue
Can’t be ruled out!
As that seems to be the consensus, I’ll pay special attention to that. I was shooting the Shield prior to, and perhaps changing guns altered my grip just enough to cause that where it hadn’t happened in the past.
Riding the slide stop is probably a good guess.
I am bad about doing this with my older SIG pistols and have to really watch my grip. With the SIGs and many HKs, you simply cannot grip them overly high like you do with a Glock. I am bad about that since the G17 and G19 are my primary shooters. From what I have read and heard from other shooters…it is very common to do this.
In retrospect, having had shot the little Shield with a high tight grip before the HK, it may have altered my grip just enough to do that where it had not before. I’ll find out next range day hopefully.
This is what caused me to stay away from the otherwise excellent and consistent PPQ. I love the grip, but a high grip means possible interference with the slide stop/release. The potential for this scares me, as I always figured I’d buy the gun, and shoot it about 500 rounds before realizing its ‘not the gun for me’. I’d rather have a gun that never locked back instead of one that does 99%. Thus, I have MPs and a G19 w/GFA. A fat right hand is my other problem. Glock bite and HP bite. Smith is fine.
A lot of guys roll the right thumb on the outside of the left thumb knuckle. It is much harder with that grip style to grab at the slide release with the right thumb.
This is what I had to start doing when I started shooting my PPQ. After shooting 4 or 5 mags with consistent failure to lock back I realized it was me and made the necessary correction to my grip. Hasn’t been a problem for me since. YMMV.
See if it locks back consistently firing strong hand only. If it does, it is most likely your grip with the support hand.