From what I gather, you are suppose to mount things while pressing them against the front edge of the rail so that the recoil doesn't work against them. Correct? Well, I mounted my Surefire in the VLTOR mount to my Samson rails and noticed the force of the BCG / CH slamming home bumps the mount to the rear of the rail slot. I took a wrench to it and that seemed to kill that problem, but my EOTech on my Mega upper still works itself to the rear after only using the CH a few times and I can't get it any tighter. I'm thinking the force of the CH is more violent than the recoil itself in my middy with CS recoil spring and "H" buffer...??? Should I ignore it or move things against the rearward side of the rails?

Who cares?  It effects nothing. Thats my take on it.

It's late and I'm tired but I don't really understand the issue here.

Run that by me one more time.

Apparently the bolt is kinda smallish on his mounts or the rail is out of spec and allowing his attachments to shift rearward.

Yes, the rail slots are wide enough on my Samson AND my Mega upper (both 1913 spec) that the VLTOR flashlight mount and my new EOTech 512 have room to shift between each end of the slot. I managed to get the VLTOR tight enough by putting an 11/32 wrenh to it, but the EOTech still workes itself rearward by dropping the CH on an empty chamber for dry fire practice. I'm wondering if it won't just drift back and forth between dropping the CH and the recoil of live fire thus wearing shit out...??? Reason I thought it mattered is because I know I've seen it posted here that this is how you are suppose to mount things to the rails, and I think it's in the TM somewhere as well.

yes it is a concern... things should not move on the rail, especially under simply dropping the bolt.

The cross cuts are for recoil lugs, evaluation of early failure of some parts indicates that the shifting as you describe causes an excessive shock to items, if they are allowed to reach the point where the move from one side of the cut to the next.

Trust me... design engineers and CAD/CAM programmer/operators are not payed the wages they get so that someone can say "it is close enough" -- sloppy fit and out of spec parts may be okay for some people, but why?

Maybe it's just me but if your EOTech is able to move on the rail when dropping the charging handle then it's no where near tight enough.  Either that or your rail is way out of spec.

When mounting my 552 I place it on the rail, push it forward as far as it will go and tighten hand tight and then use a coin to tighten it another 1/2 to 3/4 turn.  This is probably tighter than what EOTech recommends but it works.  As of late I also put a drop of blue Loc-Tite to ensure that the thumb screw does not loosen up on me.

As far as Loc-Tite goes you may be able do without it but if you shoot a few thousand rounds the EOTech screw will eventually loosen up, maybe in even less rounds if it's not on tight enough to begin with.  I very rarely remove my EOTech but even with the blue Loc-Tite it's still pretty easy to remove it when needed.

I've been using the EOTech 552 since Rev D and over the years these are things that I've found to keep my EOTech mounted securely, YMMV...

Well, am I just the only one who noticed that their $300+ optic does this or am I the only one with the problem? I don't get it...the knurled weaver bolt of the EOTech is designed to be tightened by hand with a coin, I took it a step further and put some pliers to the coin for an extra 1/4 turn and this still happens. Same with the VLTOR mount...it's designed to be hand tightened only, yet the damn light worked itself out of the mount in just 1 mag before I took the wrench to it.

Only thing I can think is I have that David Tubb's CS ISMI flat-wound recoil spring that prob. puts a little more ass on the BCG slamming home.

Quoted: Well, am I just the only one who noticed that their $300+ optic does this or am I the only one with the problem? I don't get it...the knurled weaver bolt of the EOTech is designed to be tightened by hand with a coin, I took it a step further and put some pliers to the coin for an extra 1/4 turn and this still happens. Same with the VLTOR mount...it's designed to be hand tightened only, yet the damn light worked itself out of the mount in just 1 mag before I took the wrench to it. Only thing I can think is I have that David Tubb's CS ISMI flat-wound recoil spring that prob. puts a little more ass on the BCG slamming home.

I've heard of the EOTech canting but I've never heard of one, when tightened properly, that would move when the charging handle is dropped.  No action spring should be strong enough to move a properly mounted optic when dropping the charging handle.

If it does the same thing on other uppers I'd recommend a cal to EOTech.

EOTech recommends turning the bolt till you feel resistance then take it another 3/4 turn with a coin. They also advise against loc-tite. I could only get anothe r1/2 turn by hand so I had to take pliers to the coin to get to 3/4 and this is the point at which the god damn coin itself started to twist. I don't think it's getting any tighter.

Possibly a combo of the stronger spring, enhanced BC, "H" buffer, and the fact that the MEGA upper is teflon impregnated?

Quoted: EOTech recommends turning the bolt till you feel resistance then take it another 3/4 turn with a coin. They also advise against loc-tite. I could only get anothe r1/2 turn by hand so I had to take pliers to the coin to get to 3/4 and this is the point at which the god damn coin itself started to twist. I don't think it's getting any tighter.

I know they do but it works...  

In my experience it doesn't hurt a thing and when you remove it the only thing you need to do is to make sure to clean the screw threads before applying a drop of Loc-Tite and re-tightening it.

Quoted: Possibly a combo of the stronger spring, enhanced BC, "H" buffer, and the fact that the MEGA upper is teflon impregnated?

As I said above, a properly mounted optic should still not move...

Quoted: Quoted: Possibly a combo of the stronger spring, enhanced BC, "H" buffer, and the fact that the MEGA upper is teflon impregnated? As I said above, a properly mounted optic should still not move...

Exactly, which is why I made this post.

Quoted: Quoted: Quoted: Possibly a combo of the stronger spring, enhanced BC, "H" buffer, and the fact that the MEGA upper is teflon impregnated? As I said above, a properly mounted optic should still not move... Exactly, which is why I made this post.

If you've tried in on another upper and it still does the same thing then it might be time to give EOTech a call...

I don't have access to another upper, but I do have a Samson FF rail. I'd think a replacement would do the same thing since they are so precision anyway. I dunno man, guess I'll see how she does on the next range session. If it doesn't float back to the front under fire, I'll just mount everything against the rearward part of the slots.

Actually, you should push it forward towards the muzzle as you tighten up the mount.  Recoil will naturally want to push the gun back so you want to to get it tight so that there's no space for the mount to shift.

If your EOTech is still moving around you really should call EOTech and see what they can do and stop ASSUMING that a replacement will do the same thing.

I know it...in fact, I've called EOTech about twice a day since before SHOT and NEVER get an answer.