Anyone ever experience issues on a Glock after adding optics?

**jthrelf** · December 5th, 2020, 09:50 PM

I added a Holosun to an aftermarket Glock slide, tried it on a Glock 26 Gen 4 lower, factory barrel and had 2 failures out of about 30 rounds today (yup, only 30... Thanks 2020). I didn't want to continue without troubleshooting a bit first.

The first failure I can't recall exactly what happened, but I thought I didn't seat the mag because the first round went off and then it was a click. When it happened again later on I saw a light primer strike on the round. I feel like the slide got bound up a bit too, but again I can't totally recall and didn't want to burn up more ammo replicating. I think the strike was also off-center.

Here are the facts:

Rockslide USA RMR cut slide, factory Glock barrel, factory Glock lower - all factory standard internals. The Glock lower has never experienced a malfunction over the years.

The slide has been used with a different, aftermarket barrel on another lower in the past with no issue, as well as a few rounds on this lower. But this is the first time it was used with the Glock factory barrel, and with the Holosun mounted.

Also not an ammo or mag issue. The one failure was WWB 115GR in a Pmag, the second was with Gold Dot 124gr in a Glock mag.

Is this a lockup/fitment issue where the mating tolerances of this new slide/barrel combo are slowing the slide down just a touch and not putting it fully into battery, causing the light strike? Essentially an example of tolerance stacking? The barrels each drop in nicely to each slide.

Could the optic weight also be factoring in somehow? I know typically the cut of the slide and the optic offset each other in terms of weight, so the standard recoil spring should work. When the slide was run previously it had a cover plate.

I'm a bit bummed because I was looking to carry this combo and of course that's on hold now.... and probably until ammo isn't $0.60 since I'll have to run a few hundred flawlessly after this suboptimal performance.

**red dog** · December 5th, 2020, 10:30 PM

Try it with the previous after market barrel that worked with that slide. If it works bob is your uncle. If not go with the recoil spring, change it out and see. When you start using aftermarket parts that are (drop in) your gonna have potential issues. Unfortunately your gonna have to burn some ammo to figure it out.

**jthrelf** · December 5th, 2020, 11:22 PM

Originally Posted by red dog

Try it with the previous after market barrel that worked with that slide. If it works bob is your uncle. If not go with the recoil spring, change it out and see. When you start using aftermarket parts that are (drop in) your gonna have potential issues. Unfortunately your gonna have to burn some ammo to figure it out.

Yeah trying the other barrel was my next move. It's just unfinished, polished stainless though which I don't like on that color combo, purely for cosmetic reasons. But it would help rule things out.

**HanzMcFeely** · December 12th, 2020, 10:40 PM

Originally Posted by jthrelf

I added a Holosun to an aftermarket Glock slide, tried it on a Glock 26 Gen 4 lower, factory barrel and had 2 failures out of about 30 rounds today (yup, only 30... Thanks 2020). I didn't want to continue without troubleshooting a bit first.

The first failure I can't recall exactly what happened, but I thought I didn't seat the mag because the first round went off and then it was a click. When it happened again later on I saw a light primer strike on the round. I feel like the slide got bound up a bit too, but again I can't totally recall and didn't want to burn up more ammo replicating. I think the strike was also off-center.

Here are the facts:

Rockslide USA RMR cut slide, factory Glock barrel, factory Glock lower - all factory standard internals. The Glock lower has never experienced a malfunction over the years.

The slide has been used with a different, aftermarket barrel on another lower in the past with no issue, as well as a few rounds on this lower. But this is the first time it was used with the Glock factory barrel, and with the Holosun mounted.

Also not an ammo or mag issue. The one failure was WWB 115GR in a Pmag, the second was with Gold Dot 124gr in a Glock mag.

Is this a lockup/fitment issue where the mating tolerances of this new slide/barrel combo are slowing the slide down just a touch and not putting it fully into battery, causing the light strike? Essentially an example of tolerance stacking? The barrels each drop in nicely to each slide.

Could the optic weight also be factoring in somehow? I know typically the cut of the slide and the optic offset each other in terms of weight, so the standard recoil spring should work. When the slide was run previously it had a cover plate.

I'm a bit bummed because I was looking to carry this combo and of course that's on hold now.... and probably until ammo isn't $0.60 since I'll have to run a few hundred flawlessly after this suboptimal performance.

The only suggestion I have is to check the length of your mounting screws on the holosun and make sure they aren’t too long, causing issues with binding at the ejector rod.

I can’t say for certain that this is the issue, as I’ve never used a rockslide RMR cut upper (I went with LJ’s AR cut for vortex viper) but if the drill holes go completely thru the slide you could be binding up there against the ejector or the safety plunger rod. You may have to contact rockslide to get the proper mounting screws (I had to order special sized ones from LJ’s for mine and use those instead of what came with the Viper)

Also as mentioned try a different guide rod assembly. Definitely suggest stainless steel if you haven’t already upgraded. Squirrel daddy makes a decent one for glock with a flat wound spring and is cheap. I have about 1500 rounds on mine with no issues using a factory glock 17 threaded barrel

**jthrelf** · December 13th, 2020, 09:40 AM

Originally Posted by Woodwanderer

The only suggestion I have is to check the length of your mounting screws on the holosun and make sure they aren*t too long, causing issues with binding at the ejector rod.

I can*t say for certain that this is the issue, as I*ve never used a rockslide RMR cut upper (I went with LJ*s AR cut for vortex viper) but if the drill holes go completely thru the slide you could be binding up there against the ejector or the safety plunger rod. You may have to contact rockslide to get the proper mounting screws (I had to order special sized ones from LJ*s for mine and use those instead of what came with the Viper)

Also as mentioned try a different guide rod assembly. Definitely suggest stainless steel if you haven*t already upgraded. Squirrel daddy makes a decent one for glock with a flat wound spring and is cheap. I have about 1500 rounds on mine with no issues using a factory glock 17 threaded barrel

The screw holes do not go completely through the slide.

At this point I'm really thinking it's break-in needed for the barrel slide fit. I'll have to sacrifice some ammo to keep trying a bit more. I tested and the guide rod always returns it to battery using the gravity test, but also something to keep in mind so thanks!

**jthrelf** · December 14th, 2020, 01:23 PM

Put $12 of ammo aka 20 rounds

through the rock slide upper with aftermarket barrel (which that combo has been good in the past) and all was good. Small sample size but it's encouraging and will continue to put rounds downrange.

**aubie515** · December 14th, 2020, 02:43 PM

I have a few Holosun optics on my Glocks and not one issue, so I'd say your slide needs some rounds through it.

**340M&P** · December 14th, 2020, 03:18 PM

No issues with my Trijicon RMR but it's on a G17 slide so not apples to apples. Maybe rack the slide a couple hundred times to "break" it in. Cheaper than shooting it anyway.