Burris Fastfire III won't hold zero

[GetmeoutaCT]

I just put my two-year-old FFIII on a Glock 19 MOS. Great sight but will not hold zero. After a couple of mags of standard 115gr target-grade ammo it's off, meaning it's back to the green-dot bore sight to line up the red and green dots.

I know a red dot is more stressed on an auto pistol than a revolver due to the reciprocating slide, but this is unacceptable. Anyone else have the same problem? Also, I was hoping to avoid the $600 outlay for a Trijicon RMR but will do so if it is more rugged in this regard.

Thoughts? Thank you-

 

[ClickClickD'oh]

I run a fastfire III on my Five-Seven and an AR-F3 on my rifle. Neither have ever had problems with wandering zeros. Are your mounting screws threadlocked in place?

 

[GetmeoutaCT]

That's what I'm going to address first. The screws Glock supplies to mount the sights to the supplied plate (which are coated with a blue substance; presumably Locktite) were too short, so I used the screws originally supplied with the sight to mount it to the plate. However, not having any locktite, I just screwed 'em in. The sight is not noticeably loose, but I guess that doesn't tell the tale.

I found a thread on Glock Talk started by someone with the same issue; he supplied a link to Amazon for the purchase of what he said are the best screws for a FF III and a Glock MOS. I'm waiting for those and will try them with locktite.

I guess I'm looking here for folks who might have eliminated the mount as an issue but whose FF III is still not holding zero. Trying to save myself some time before biting the bullet (so to speak) and springing for the Trijicon.

 

[GetmeoutaCT]

I run a fastfire III on my Five-Seven and an AR-F3 on my rifle. Neither have ever had problems with wandering zeros. Are your mounting screws threadlocked in place?

...although I will say, having fired a five - seven, that is a sweet pistol with very low recoil - much less than a Glock 19. Very interesting round, also.

If I still lived in a free state I would consider a five -seven (hence my forum name); however, being limited to ten rounds leads me to shun full-size grips that I cannot take full advantage of. It may just be stubbornness on my part, but I refuse to buy a handgun that I can only load (in this case) to half-capacity.