Just mounted a new ARMS #19 ACOG on a Rock River flattop upper, but once the throw levers were in the locked position, it was extremely difficult to unlock the levers so I can take it off.  Is this normal?  There was substantial resistance when trying to put the throw levers in the locked positionas well.  

I actually had to pry the levers away from the unit with a flathead screwdiver, which I cover with ducttape so it would not mar the finish.

Your thought?

What kind of rail is it being mounted to? I had a set of #22 rings that installed and removed really well on a BM flattop, but were hard as hell to do the same on a GG&G fire rail.

I've got a #19ACOG on my FAL and yes, they lock real tight - that's a feature - and I use a tiny (plastic) prybar to remove them come time.

RRA and GG&G are not known for certified mil spec 1913 rail dimentions. The Colt, ARMS, Armalite, Bushmaster, FNMI, and other gov't contractors do have the correct rail dimentions as they must go thru gov't inspection, and after market companies do not.
Good Shootin, Jack

Well, since I am breaking down all my rifles this winter and refinishing some and camo-finish others, I'll have a chance to see which of my A3 receivers(4 to choose from) has the best fit with the ACOG #19.  Since this was my first expereince with throw-lever mount I was not sure what to expect.

Thanks,

PS.  Paul, I originally try, what I thoughtwas a sturdy peice of plastic as well, but it broke trying to pry the lever open.  I can't move the levers at all with my fingers in the locked position.

I have the #19ACOG as well as 2 other throw lever mounts.  They are all stiff  as whipped egg whites when new, both going on and coming off.  After about 15-20 on/off cycles on the interface, you won't need any tool unless you are 98 pounds of Charles Atlas "before" material.

No cause for concern.  The return to zero is remarkable !