scope mounting question for rifle shooters

A question for those that have scope mounted target rifles.  Mounting a scope on a target rifle usually involves checking the alignment of the rings and lapping them to make them perfectly in line. Usually target rifles use two separate bases because of the scope length but a one piece base can be used on the shorter scopes. I understand the concept and have done it but never knew what would happen if I or anyone were to mount a scope on rings that when mounted were not inline.  My question is bullseye related because I haven't heard anyone doing it on pistol. I'm looking for the cause that would make a high end red dot change zero on a good grouping BE 1911 for no reason, when zero is adjusted again will remain OK for a while then change again after a few matches. If this were a problem experienced by a new shooter I wouldn't pay it much attention but I'm told of this by more than a few High Masters 2650+ shooters.
 I'm sure that the top of a 1911 slide is straight but I will check a few, A slide mount base should be straight but is it? However the rings do interest me in that I'm sure a set is made up of a pile of rings made at different times by different machine operators and possibly different machines.
 So does anyone know the results that would happen if someone were to purchase a good target rifle pre drilled for scope base, a high end target scope a good set of rings and bases and mounted them with out checking alignment and it was not aligned?

Frank, I have never seen it make any difference. The scope even if aligned perfectly has to be adjusted out of line to compensate for the bullet drop. Is there really any difference between being in-line horizontally or vertically? The very few times I have had to work with adjusting a base was with bases so far out of alignment that the scope was not adjustable. YMMV

I am with Len on this.  Yes it would be nice if the scope zero'ed near the center of it's range and you were planning to make range adjustments from in close to those very long 1800 yard shots.  The only thing I worry about is that the scope is in the rings so it is plum with the frame.  The higher the scope is from the bore the my critical it is when changing ranges.  I have levels on several of my pistol scopes and all my rifle scope.  With a pistol benchrested I can tell a difference if I cant the pistol a little.  Don

If you mount the rings on the rib and finger tighten them.  Then mount the optic and tighten the rings next go back and do the final tighten on the rib mounts. Now all you have to worry about is the optic pointing left/right and it should be adjustable.

Mounting the rings on the rib tight before mounting the optic you could potentially put stress on the optic's tube.  This is because one mount may be pointing slight right and the other slight left.  Not sure but I'd guess this could lead to scope/dot issues.

The farther apart the rings (rifle) the more critical this becomes. 

I used a ring alignment tool to mount my rings before attaching the optic - overkill on a pistol.
- Dave

I have no problem making a base and cutting the angles needed to mount the rings while on the slide so that it's perfectly in line with the barrel bore.
 That's not what I'm asking, if the rings are not inline they will want to put stress on the scope! Lets use something else, when boring holes to mount bearing they must be inline, if not stress  that's put on the bearing will damage them. Eventually the shaft will break! The bearing in an engine must be line bored, that means all of them are cut inline and if not the bearing will self destruct eventually the crank will break! Pillow blocks have a radial mount similar to a Briley Bushing, if the rings were similar to Briley Bushings they will self align similar to a pillow block! No stress will be put on the scope, that has nothing to do with the impact. The alignment I'm talking about would be similar to if I took a 1" thick plate and bored 2 holes 1.001" and 6.000" apart. and another with the same hole size except 6.010" apart. If I put the two plates together I can't put a 1.000" pin thru the holes, but if I separate them lets say 12" I can press the 1" pin thru. But they will be straight in the holes but will bend in the 12" distance between the plates. Rings out of alignment will do the same to a scope! I know what it will do to shafts and bearings, what will it eventually do to a scope??

Precision rifle shooters will ream and lap their scope rings before installing the scope. There are many benefits, but mainly increased accuracy from not bending the scope tube and damaging the scope. The same principals can be applied to red dots in bullseye pistol.

Ghillieman wrote:Precision rifle shooters will ream and lap their scope rings before installing the scope. There are many benefits, but mainly increased accuracy from not bending the scope tube and damaging the scope. The same principals can be applied to red dots in bullseye pistol.

How they check that the scope is circular and match the rings to the scope?

Vee-block and dial indicator.

I do understand that Ghillieman, but what will happen to the scope over time? I understand how lens work and how zero is changed in a scope.
 For example if I take a set of rings, mount one to a base that's attached to a solid fixture and check the height with a digital height gauge accurate to a thousandth of an inch and measure the height,check another and it's .050" lower (bit of exaggeration but it's only an example) Chang the machine operator was having a bad day!  I take the 2 rings and mount a scope on my 1911 adjust 0, put it in my gun box for a month or so, using the same ammo I used to adjust 0. What should I expect to see? I know what to expect to happen if I did the same with an Aluminum tube, it will be slightly bent but over time it will conform to the offset and match the .050 offset but with lenses mounted in the tube and recoil adding vibration. Plus putting the gun in the trunk on a hot day which is like an oven. Will it make a high end scope like the 9000SC change zero from centerfire day to 45 day a few inches?

Someone should run tests where the take the gun from the fridge to the range, then somewhere warm to the range. Is it the scope that is moving with the conditions of it or metal of the rings and scope? I'm no metallurgist not sure the effects at those temps. Is it maybe barometric pressure effect on ballistics? 

Aimpoint operating conditions. Temperature range operation: -30°C to 60°C (-20°F to 140°F)

That temperature difference can effect some powders causing 2" differences.

Mount scope. Sight in scope. Pull trigger. Shoot 10's!

Yeah I'm sure someone could damage a scope when mounting it, but put the thing on and shoot it! I see more problems with mounts/bases than scopes/rings.

Jon

For long distance shooting with rifle scopes, you definitely want to lap the rings and bias them forward when tightening them down. There are kits available for many sizes of rings. It is easy and can only help.

Joel

Barometric pressure change will be predictable like the Sun location has on iron sights. Temperature change should be too but if the scope were loctited into the rings and not free to move the stress created by the difference in expansion between Aluminum and steel might cause the loctite to release in the same way that causes the ticking sound when something heats up. Then when cooled not enough force it there to allow it to return.
 What I'm thinking is what if there is stress created by misalignment. I remember my father putting 2 pieces of wood 2X4 sized about 12' long on cement blocks 12' apart with the 4" side on the blocks. I seen it and removed them, my dad put them back, I did it again, don't remember how many times this went on until my father said why are you taking my wood off the blocks? I said if you leave them like that they will bend, he said that's what I'm doing. Later I was surprised as to how much bend he was able to get.
 I know what will happen if I were to put a scope on rings of different height, if I had some instrument like an Ultra Sound and could see through the Aluminum the scope will be touching the rings on the edges and a gap on the other side. Eventually the force created by the screws on the other half of the rings creates a periscope. Is it possible that the friction on the upper ring and the fatiguing Aluminum scope tube cause a heater like tick sudden movement possibly helped by rapid fire make the scope tube bend suddenly creating a 50 yard zero change at the next match? May not be just rings but the combination of base, mounting and rings could cause the problem experienced High Masters are having with the 9000SC.

Darn why did you have to bring this up i just bought a 9000SC and but it on my Nelson now I got something else to worry about.  It is bad enough that the thing eats batteries.  Don

Magload wrote:Darn why did you have to bring this up i just bought a 9000SC and but it on my Nelson now I got something else to worry about.  It is bad enough that the thing eats batteries.  Don

Aimpoint that eats batteries ? Never heard of that better send in for repair

Chris Miceli wrote:

Magload wrote:Darn why did you have to bring this up i just bought a 9000SC and but it on my Nelson now I got something else to worry about.  It is bad enough that the thing eats batteries.  Don

Aimpoint that eats batteries ? Never heard of that better send in for repair

I am hoping the battery that came with it was junk.  I am already turning it to 8 to get a dot.  Had to get batteries online none of the stores here had them.  I believe they are old camera battries and not a lot of people use those cameras anymore.  I will know better when I put one of these new ones in.  Don

Oh the fact you can't see a dot below 6 isn't uncommon. I use 6-8 as setting pending in light conditions. Remember these scopes are also lent to be used under magnification. But you should get 5000 hours off the battery

Chris that is good to know thank you.  Been wondering how to mount that 3X magnifier on my Nelson. 

Chris Miceli wrote:

Ghillieman wrote:Precision rifle shooters will ream and lap their scope rings before installing the scope. There are many benefits, but mainly increased accuracy from not bending the scope tube and damaging the scope. The same principals can be applied to red dots in bullseye pistol.

How they check that the scope is circular and match the rings to the scope?

Chris if that was an issue there would be several companies that offer a gage to check your scope. Being that it's not out there leads me to believe that it is just not an issue. However a quick search will bring up all sort of tools to ream and align scope rings.

Froneck wrote:I do understand that Ghillieman, but what will happen to the scope over time? I understand how lens work and how zero is changed in a scope.
 For example if I take a set of rings, mount one to a base that's attached to a solid fixture and check the height with a digital height gauge accurate to a thousandth of an inch and measure the height,check another and it's .050" lower (bit of exaggeration but it's only an example) Chang the machine operator was having a bad day!  I take the 2 rings and mount a scope on my 1911 adjust 0, put it in my gun box for a month or so, using the same ammo I used to adjust 0. What should I expect to see? I know what to expect to happen if I did the same with an Aluminum tube, it will be slightly bent but over time it will conform to the offset and match the .050 offset but with lenses mounted in the tube and recoil adding vibration. Plus putting the gun in the trunk on a hot day which is like an oven. Will it make a high end scope like the 9000SC change zero from centerfire day to 45 day a few inches?

I wouldn't expect that much zero shift. What needs to happen is they rezero the optic and then count the revolutions and clicks to a mechanical stop on elevation and windage, write it down. The next time they experience the zero shift go to the same mechanical stop and see if the adjustments are the same. The optics could be jumping a thread during recoil, or worse...

Not sure what Aimpoint it was that eats batteries. AMU had another model that did eat batteries, if the dot was not turned off when going down range to score the battery would not make it thru the 900. I understand the newer models were fixed. 9000SC the battery lasts forever it seems!
 I doubt it's a stripped screw, that would require quite a bit of force, maybe one was defective but all ten have the same problem! The 9000 series is for rifles so I don't think recoil is doing it.

Maybe so Frank. An optic on the slide of a pistol is receiving a sharp recoil in both directions and moving much faster and further than with a rifles recoil. I have noticed the aimpoint micro I have mounted on my 1911 slide seems to be throwing some oddball group shifts. Very small shifts, maybe one side of the 10 ring or the other. All I know is that I never seemed to have that problem with a frame mounted optic. I cant say for certain, but I have noticed small zero shifts, nothing like what you describe with the AMU. I would like to know what they come up with.

Ghillieman wrote:Maybe so Frank. An optic on the slide of a pistol is receiving a sharp recoil in both directions and moving much faster and further than with a rifles recoil. I have noticed the aimpoint micro I have mounted on my 1911 slide seems to be throwing some oddball group shifts. Very small shifts, maybe one side of the 10 ring or the other. All I know is that I never seemed to have that problem with a frame mounted optic. I cant say for certain, but I have noticed small zero shifts, nothing like what you describe with the AMU. I would like to know what they come up with.

from aimpoint

Shock: The unit is operable before and after shock. Limits: X-axis: 500 g, 0.7 – 1.1 ms (3 shocks), Y-axis: 40g ±4g, 11 ±1ms (2 shocks in each direction, Z-axis: 40g ±4g, 11 ±1ms, 2 shocks in each direction. Functional during exposure (room temperature)

Vibration: The unit operates despite vibration. Limits: Vibration, sinusoidal in a frequency range of 10-150 Hz. Frequency: 10-30 Hz, ±1.587 mm, Frequency: 30-150 Hz. 5.75 g, 1 octave/min

Ghillieman wrote:Maybe so Frank. An optic on the slide of a pistol is receiving a sharp recoil in both directions and moving much faster and further than with a rifles recoil. I have noticed the aimpoint micro I have mounted on my 1911 slide seems to be throwing some oddball group shifts. Very small shifts, maybe one side of the 10 ring or the other. All I know is that I never seemed to have that problem with a frame mounted optic. I cant say for certain, but I have noticed small zero shifts, nothing like what you describe with the AMU. I would like to know what they come up with.

When you mount an optic, you should bias it forward (apply pressure forward) when tightening. This will eliminate any movement due to recoil. There are too many shooters that don't notice a shift in their zero so perhaps your unit was defective. Also, the recoil going backwards is much harsher that forward. Yes, I would imagine that a frame mounted optic would have less issues due to recoil.

Joel