Movement of mount on rail

[jelenko]

Has any one had experience with a Bobro mount moving on the rail?

I have a Bobro Precision, 1 lever mount. On some brands of scope riser rails [i.e., on 4 different GGG and a WOA one] I can get it to rotate left to right a very small distance [on the order of 1/16" or a touch less] by applying ~ 20 lbs of force to the mount => I'm assuming it will move under recoil of a 223.
On different rails [a different WOA one and on my two Weaver's] I cannot detect any movement at all.
When I let go of the mount, it clearly returns [close] to the original position. The question is how close to the original position.

The best answer, of course, is to just use ones with no movement. But, GGG and Bobro are such well respected brands, I'm wanting to confirm it this is common and nothing to worry about - for accuracy requirements in the .5 - .6 MOA range. I.e., not benchrest accuracy.

Thanks!

 

[fkimble@charter.net]

Can you not tighten up the quick lever mechanism? Sounds like some of your rails are not the same width.

Frank

 

[dthomas]

No amount of movement is acceptable

 

[jelenko]

Can you not tighten up the quick lever mechanism? Sounds like some of your rails are not the same width.

Frank

The Bobro ones don't have an adjustment for the lever like the ADM ones do.

Hmm. I should check the width of the ones that allow movement to ensure they are in spec. I just assumed that anything from GGG or WOA would be in spec.

ETA. Sumbitch. The GGG's are 12 thousandth's under min for the width [.818 vs .830 min spec] and .033 OVER the max width at the 'base'. I don't have the WOA rail anymore that was also loose.

The two Weaver scope risers are both within spec on those two dimensions.

 

[jelenko]

No amount of movement is acceptable

That's what I'm thinking.
I asked Bobro - their answer was not confidence building. ETA. See my above edit about dimensions of the GGG scope riser bases. Can't hold Bobro responsible for out of spec rails.
He first said that anything would move with enough force - even though I had stated that it was moving with just ~ just lbs.
My take so far is Bobro is not aware that their mount doesn't work with some in spec rails [at least I'm assuming that GGG's and WOA's are to spec].


I'm going to try one of Bobro's scope riser bases and try a pair of Warne QD rings.
I really like the ADM QD mounts but they're a little tough to take off to change the scope position during a match.

 

[chkunz]

I have been using the Bobro single lever mounts for many years and on several guns/rails/scopes and have never had any movement. I take the scope off the gun when I am done shooting and it goes in a bag then back on when I am ready to shoot. I have tested them for consistent zeros and never have detected a zero shift. Bobro is a quality product and the rail must also be high quality with good tolerances also for consistent zeros. It is all about tolerances and I would look to find a tolerance issue with the rail.

 

[jelenko]

I have been using the Bobro single lever mounts for many years and on several guns/rails/scopes and have never had any movement. I take the scope off the gun when I am done shooting and it goes in a bag then back on when I am ready to shoot. I have tested them for consistent zeros and never have detected a zero shift. Bobro is a quality product and the rail must also be high quality with good tolerances also for consistent zeros. It is all about tolerances and I would look to find a tolerance issue with the rail.

Yeah. I just measured the GGG ones. They are out spec on at least two dimensions! See my edits in the above post.

I've emailed GGG.

 

[Sandstorm]

You'd be surprised how many aluminum rails are warped or slightly bent..not even getting
into the tolerances....... ( Its not the problem with the mount )
Lubricating the mount contact points will help it self center better on the anodized rail
but if the rails not straight...your beatin a dead horse.....just my 2c

 

[Intell]

I have an ADM quick release mount that is returning to zero when removed and reattached. The levers need to be tightened in the same order. I’ve only tried it 3 times so more testing is needed.
I have another rifle I tried it on and it did not, it was close enough to hunt with, but it was 3/4” off. Maybe some adjustment is needed for that rail.
I will say I’ve have a few other brands and never trusted them to go back to zero, I always checked them first.
I’ll be buying ADM if I need another QR mount.

 

[jelenko]

Update. My bad. The Bobro mount is not moving on the riser rail.

I had been testing it with the scope on the rifle. Of course, I had to hold the rifle still while pushing on the mount. To eliminate the possibility that the rifle was moving a bit, I took the rail off and just tested with the scope and the rail - absolutely no movement.