strange RMR zero shift on G34

[TobyJ]

I'm running an RMR type one on my glock 34, mounted to a zev slide. A couple weeks ago, I started my drills with a few rounds to verify the zerio, and it was shooting about an inch low at 10 yards. I re-zeroed it, and ran about 300 rounds through it without issue. I shot three matches (about 400 rounds) the following week, and all ran well. Last Friday, I started my drills the same way, sight was still zeroed, and this time, put a dab of nail polish on the windage and elevation adjustment screws, as well as the two mounting screws. Shot 2 matches over the weekend, Mostly paper targets, and I hit about my normal A to C ratio, so nothing jumped out. Also went 1 for 1 on all steel, including a texas star.

 

Tonight, I shot a local steel match, and had a lot of trouble with smaller targets, that normally don't give me trouble...plate racks at 10 yards, and hinged 6" circles from 10 to 25 yards. I seemed to be low on everything. Took the gun up to the main range, and sure enough, it was shooting about 2 inches low at 11 yards. Checked my witness marks, and all is lined up. Group was also very tight, not drifting...just 2 inches low. Windage is spot on.

 

I'm thinking the RMR is going south, but I'm not sure exactly how. I did the google search thing, and I didn't find a lot of documented RMR failures. the majority of the failures I could find are blinking / flickering /electronics type stuff. I did find a couple posts about the adjustment screws wandering under recoil, but mine did not move. I also found one post where the adjuster broke, but it caused the shots to string as the dot 'fell'...not just shift poi vs. poa.

 

I have another RMR that I can swap in, and probably will...Area 2 is coming up. My fear there is that other than this...whatever it is...this particular RMR has been rock solid for something north of 20k rounds. So, before I went that route, I figured I'd check here, to see if anyone had any other ideas.

 

Thanks

TobyJ

[Hi-Power Jack]

Took me by surprise, but when my C-More drifted a few years ago on my TruBor,

it turns out the culprit was the grip screws were loose     

 

Tightened them down with some glue, and five years later they're still good      

[mwc]

Watching this... I too would like to hear about RMR longevity.

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[tdp88]

Just put the back up dot on and send your RMR back to Trijicon. If you're going to shoot carry optics, I think it would be smart to have two guns set up and use one as a practice gun and one as a match gun. 

[Rnlinebacker]

what poundage recoil spring are you running?

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[Beef15]

Send it in. If the lens shifts that is what happens. I don't have an RMR imagine it's glued in like most. Suppose some other component could move also with the same result.

 

My viper had "adhesive failure" you could see the adhesive had changed, but I couldn't remember if it was clear in the first place, it was. Initially I had a minor shift to the left, adjusted, shot a match all was well for a few hundred rounds, then at another match missing everything left, adjust, good for a stage, adjust, no good, and ran out of adjustment. It really sucks when the failure leaves the dot on, had I for sure realized what was happening I would've been better turning it off. Have seriously considered a front sight since that day.

 

If I did a lot of lvl 2+ I'd go Hwansik style and have 3 optics, two zeroed on the gun and one for whichever is going back to the manufacturer. They all fail, some more than others. 

[TobyJ]

1 hour ago, Beef15 said:

Send it in. If the lens shifts that is what happens. I don't have an RMR imagine it's glued in like most. Suppose some other component could move also with the same result.

 

My viper had "adhesive failure" you could see the adhesive had changed, but I couldn't remember if it was clear in the first place, it was. Initially I had a minor shift to the left, adjusted, shot a match all was well for a few hundred rounds, then at another match missing everything left, adjust, good for a stage, adjust, no good, and ran out of adjustment. It really sucks when the failure leaves the dot on, had I for sure realized what was happening I would've been better turning it off. Have seriously considered a front sight since that day.

 

If I did a lot of lvl 2+ I'd go Hwansik style and have 3 optics, two zeroed on the gun and one for whichever is going back to the manufacturer. They all fail, some more than others. 

 

I think lens shift is a possibility, although I haven't heard this much with RMR's.  I had the glass completely fall out of a viper, and right before it did, my shots were all over the place.

 

2 hours ago, Rnlinebacker said:

what poundage recoil spring are you running?

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I ran a 13 lb for the last 18 months or so, but then switched to an 11 on advice from Zev, when I put the prizefighter slide on.  Interestingly enough, the first shift down I saw was the day I put the 11 lb. in.  That same 11 lb spring is still in there, and while I can't figure out exactly how a weaker spring (either from changing or from use) could drop POI, I am heading to the range this morning, and will test the gun as it sits (was 2 or so inches low last night) vs. new 11lb. spring, vs. new 13 lb. spring.  I don't really expect to see a change, but I want to cover as many bases as I can.

 

 

2 hours ago, tdp88 said:

Just put the back up dot on and send your RMR back to Trijicon. If you're going to shoot carry optics, I think it would be smart to have two guns set up and use one as a practice gun and one as a match gun. 

 

I suspect that this will be the outcome today.  I already carry just about every spare part, and was planning on zeroing this backup on the original MOS slide, so that I could make a quick swap.  Hadn't really thought about a 'match' gun vs. a 'practice gun', but it's an idea.  For me, it would be more of a 'big match' vs. a 'small match / practice gun', as I shoot at least one match of some kind or another, each week.

 

Thanks for all the input

 

TobyJ

[TobyJ]

yep...looks like my primary RMR is going back to Trijicon.  About a month ago, I thankfully bought a spare.  I mounted it, zeroed it, then took it off and put the primary back on.  Hit the range today, and the primary group was nearly 4" low POI vs. POA.  Put the backup on, and it was pretty much dead on.   

 

So confirmed the primary was off, and that the ZEV slide is keyed well enough to allow a sight to be removed and replaced without significant shift of zero.  

 

Also confirmed that while they are pretty tough, RMR"s are subject to failure.  This one has been on the gun for close to 18 months, and well over 20k rounds, so I'd say that's pretty solid.

 

TobyJ

[9x45]

It's is usually loose screws.

[WVGlocker]

Just had this issue with my G32 carry gun.  Didn't have an issue last time I shot and then noticed the dot was well above my irons (I have suppressor sights for a backup).  Checked zero last night and I was almost a foot low at 25 yds.  Running out of adjustment brought me up to 5-6" low.

I had trouble with the flickering, dead dot issue until I put a piece of rubber band behind the battery contact spring and put a drop of rubber cement under the battery, then it was rock solid for a year and a half.

Guess it's going back to Trijicon for some R&R...