Eotech 512 sliding on rail

[stwings]

Hey all,

I seem to be having issues with my Eotech 512 sliding rearward on the top rail of my upper receiver. When I mount it to the rail I make sure that it is seated all the way forward, then I torque it down. It seems to always want to walk back an 1/8 to 1/4 inch after 100 rounds or so. I've tried cinching in down as tight as I feel comfortable without over tightening it and breaking something. The rifle is a Smith and Wesson M&P15OR. Any thoughts or ideas on how to correct this?

[MichiganScott]

Eotech suggests 17 in/lbs when torquing down the mount. Do you use a torque wrench?

[cyphertext]

Is it a Sport?

Sorry, couldn't resist... saw this post over on the "expert" forum and that was one of the responses, as if because it is a Sport, the rail would be out of spec.

[Kadonny]

Another stupid question, but you are fitting it properly on the rail so the optic seats properly to the slots? Just asking because I had this happen once on one of my optics.

[Magload]

I left the cross rod, or what ever it's called, off my scope mount on my pistol and ended up picking the scope up off the floor at the indoor range.

[Maddmax]

Originally Posted by Kadonny

Another stupid question, but you are fitting it properly on the rail so the optic seats properly to the slots? Just asking because I had this happen once on one of my optics.

That was my thought too (next to proper torque). Check the side "clamps" that squeeze the rail on both sides when you tighten it down. They could be upside down and not gripping the rail like they should.

[MrG5122]

One of my 512s sits on top of a .458 SOCOM and is solid as a rock. I don't know if they are all designed the same but with mine the attachment bolt sits in a picatinny groove when secured. There is about 1/8" of forward/backward movement before it's completely torqued down. I just slide it back till it stops before the final torque. I don't see how it could move back after that without falling completely off the rifle.

[REM 3200]

Originally Posted by MrG5122

I just slide it back till it stops before the final torque.

You should move it forward(toward the muzzle) not back before final torque is applied.

[scooter123]

OK, 17 Inch Pounds is NOT a lot of Torque, it's basically finger tight. I suspect that the cross screw is not properly engaged in one of the numerous Picitinny slots. You absolutely MUST have that cross screw engaged in a slot, if you have your sight hanging of the rear of the mounting rail it's going to shoot loose. If it then hits a concrete range floor you could have a rather expensive paper weight.

[ChattanoogaPhil]

My guess is that you don't have it mounted flush on the receiver. Other than a broken mount or screw, there's no other reason it should be walking.

[JaPes]

Do as these fellas suggest, and you should be good.

If you ever feel like making your 512 a bit more useful:

EOTech Accucam QD Mount

Also these...

Scope Lens Covers - EOTech Lens Covers for Rifles & Scopes

I've installed both,and they're well worth the money.

[stwings]

Originally Posted by Kadonny

Another stupid question, but you are fitting it properly on the rail so the optic seats properly to the slots? Just asking because I had this happen once on one of my optics.

As far as I can tell I am. It's on there real solid, it just seems to walk back on the rail from the recoil.

[stwings]

Originally Posted by REM 3200

You should move it forward(toward the muzzle) not back before final torque is applied.

Yup. I hold it forward on the rail with my thumb then tighten the screw. Sorry, my post about sliding it back was incorrect.

[stwings]

Ok, I switched to the thumb screw, Pushed it forward and cinched it down good and tight after applying Locktite. Headed to the range tomorrow to see if that solves it.

[samnev]

Originally Posted by stwings

Ok, I switched to the thumb screw, Pushed it forward and cinched it down good and tight after applying Locktite. Headed to the range tomorrow to see if that solves it.

I've always used the thumb screw (a lot easier to tighten properly) on my EoTechs with the mount slid forward on the rail and never had a problem with them slipping. Torque the thumb screw to 30-40" pounds use Blue locktite and you should be OK.