I had a ARK Slide For GLOCL on my G17 GEN3 with a Mass Comp Driver.   Never fired.  The comp made it too big to holster.  I removed the comp and replaced the guide rod and the spring with a Zev 13lb (might be 11lb).

At the range I was getting slide lock on each round.

OEM spec for GLOCK 17 spring is 15-17lbs.  I think thats probably still true for an ARK slide and ARK Barrel, etc. but do you guys think a heavier spring will solve the problem?

I've written Strike about this but they take a while.

*I had this built by a gunsmith before I really knew much about good aftermarket brands or had access to Gen 5.

No, I think your lower is probably assembled incorrectly and your slide stop lever spring is above the locking block pin instead of below.

Why do you think that?  Its entirely stock gen 3 lower except for an Apex trigger and an extended mag release, all which work fine.

The gun fired fine first mag, the slide lock after the second mag and some added oil.

I know its hard to diagnose without being there.

Do you  know S.I.?

Because you said your slide was locking back with each round. That usually indicates the slide lock lever/spring being improperly installed. Or you could be doing something really weird with your grip, but that usually causes the slide to NOT lock back on empty.

There is an extended slide release on the lower.  Ill take it in.

I'm not doing anything weird with my grip - i had 2 pros shoot the gun.

Thanks man.

Try an OEM slide lock, I am not big fan of the extended slide locks as they almost make it to easy to hit in inadvertently. But I agree sounds like slide lock is installed incorrectly or some issue with the slide lock.

Strike Industries  agrees  with you.  Im buying an OEM slide lock.  

Cant help wanting to try the well-reviewed Vickers:  https://www.primaryarms.com/vickers-tactical-glock-slide-stop-vtss-001

But that could defeat the whole process of elimination.

The other theory was just that it needs to be run in.  The failures were fairly consistent: lock back.  Then it slowly started to fire off more rounds.  I didnt think I might be pressing the extended slide lock with my grip...Ill need to keep testing until its reliable.

If I buy a Vickers Tactical Slide Stop am I just repeating the same mistake?  Its not extended, and its well reviewed.