What exactly causes the ARMS mounts to come loose?

[grunz]

Can anybody point to a specific design flaw in that system that causes them to go loose?

[spr1]

They are non-adjustable, so if the rail and the mount are not happy together, there is nothing that you can do about it. I believe the levers are cast as well, so there is an increased risk of breakage.

[militarymoron]

they're non-adjustable. (edited to add - was typing this at the same time as spr1). so they can end up just right, too tight or loose on a rail depending on the manufacturing variability in the mount, and the rail - depending on which end of the tolerance they were made.

[grunz]

So they dont shoot loose over time - it's just a luck of the draw kind of thing?

[BooneGA]

My EOTech model whatever w/ the built in ARMS mounts that I am issued can move forward and rear on the upper reciever with slight pressure. Not something im terribly fond of.

But I dont run EOtechs or ARMS products on my issue or personal weapons currently either as in my opinion there are much better products available.

Rick

[ST911]

What exactly causes the ARMS mounts to come loose?

Dick Swan's engineering.

[militarymoron]

So they dont shoot loose over time - it's just a luck of the draw kind of thing?

in my limited experience, shooting by itself won't make an ARMS mount loosen, if it's tight to begin with, and that is the only factor we're considering.
yup - it really is luck of the draw - with both the mount and with the rail. i've had the same ARMS mount fit great on some rails, and too tight or loose on others, which shows variability between the rails.
mounts that are adjustable solve that issue, which is why i haven't bought an ARMS mount in years.

[grunz]

I'm stuck on the ARMS mount since it's the only option on my Elcan SpecterDR. It's just slightly loose side to side.

I wonder would there be any danger or risk if I shim the bottom of the mount with a thin rubber pad? Alternatively I could install a thinned down rail ladder protector on one of the open slots under the mount to tighten it up.

Thoughts?

[JSantoro]

If it's loose side-to-side, it's loose fore-and-aft, and unlikely that you're holding your zero as a result. Rubber will get ground through over time/rounds, I would think, but you pose a good question.

I'm not familiar with anybody shimming for the Elcan or EOTech. I've seen shimming mentioned a bit on the boards (maybe not in regard to optics mounts), so it may rate a search for references. I'm gonna call somebody who may have seen this, or what their armorer's answer to it is.

[grunz]

Riverine,

Thanks for reaching out to your friend - I'd like to hear what he says. And I'll play around with it on my end too - it's a very capable sight so I want to make sure the mounting is solid.

The other option down the road could be to contact ARMS and see if down the road they could retrofit this model with their new adjustable levers per the SHOT show thread in this forum.