installing scope/scope "cant"

[4xforfun]

Is there a better system out there for installing a scope out there than my "system"? The reason I ask is that one of my 1K comp guns sees double duty as a LR deer hammer, and it currently is throwing shots to the right as I get further out. I am 99% sure the scope is mounted with a cant to the left. I am not usually picky about my comp guns...if I can't get on target with the six min slighter period I should quit shooting. "Cant" in a comp situation just isn't that important to me.

My "system" is this.... Lets take the gun in question....BAT mod "M" with integral 20moa ring/bases. The first thing I do is set the gun in my cleaning cradle and set a carpenter level across the bottom half of the rings perpendicular to the bore. My thought is that they MUST be dead nuts on, being that they are custom BAT rings. I shim the gun in the cradle till the gun is dead level with the world. i then set the NF NSX scope in the rings and place the level on top of the elevation turret......it is plenty wide and flat enough for the level to sit solidly on it. I then gently rotate the scope till it , too, is level with the world. I may do this two or three times just to "check my work"....remove the scope and recheck the gun by placing the level across the rings, then place the scope in the rings and rotate it till it, too, is level. When both the gun and the scope are both dead nuts level with the world I consider the scope properly mounted.

Now, I am pretty sure I threw this scope on the day of a match with out doing all of the above...like I said.....dead on nuts perfect is not needed for 1K benchrest IMO.

I am about to take things apart and use my "system" to make sure things are straitened out.....just wonderin if my way of installing a scope would cut the mustard with some of you guys out there.

Thanks,
Tod

 

[Killshot]

I'm no expert by any means but I have observed that the top of the elevation turret is not always level itself.

Nightforce recommends using the flat part below the turrets to orient/level the scope to the receiver. This should bring the horizontal crosshair to level with the horizon.

 

[Longshooter70]

I use a set of feeler gauges when mounting a scope with a rail. I put the scope in the rings and use just enough feeler gauges to get between the flat bottom of the scope and the rail. Wiggle the scope around until it sits completely flat against the feeler gauges and the rail then slowly tighten the screws in your rings. Make sure you do it evenly between front and back. Make sure the gauges aren't too thick because as you tighten they will pinch between the scope and rail. If they are too thick, ease them out, take a few thousandths off and re-insert them making sure you keep them under until the rings are secure.

The way I check a scope is to take my target board at the range and staple a poster board to it. I take a level and draw a perfectly straight line up and down with a thick sharpie. I then go back to the bench and level the rifle with the crosshairs are on the line. Without moving the rifle, dial the elevation knob up and down and make sure it tracks perfectly on the straight line. If you really want to get anal, put an aiming point on the bottom of the line and shoot it. Dial up three minutes, hold the same spot and fire again. Repeat this process over and over and as long as your scope is tracking straight, the bullet impact should be on or very near the line. If it's not, the further up you dial the scope, the further the impacts will be from the line. A calm day comes in handy...

 

[K22]

Make sure you check the level on the scope as you tightened the screws - I use the "X" cross sequence to tighten the screws uniformity so I don't tilt the scope while tightening keeping an eye on the level to make sure scope remains level.

Cant is something you do not want regardless whether you're a target shooter, hunter, or just causal paper puncher.

 

[johara1]

Tod, first when bedding make fore end level then scope rail or the half of the ring like you did but use a better level. a machinist level. After it is bed,you have a level place to start from. Set the gun up on the bench and level the gun. Set a paper target back side out. With a 3-4' level draw a vertical line on the paper,add a few small aim points with a marker and one at the bottom of the vertical line. With your fore end level, set your eye relief on the scope and rotate the scope till the vertical wire is parallel to the one on the target.
Zero in on one of the dots and then move to the dot at the bottom of the vertical line and shoot 3 in the dot crank it up 20 min. and shoot
at the dot again should cut the line up high (use wind flags) then crank it down the same 20min. and they should go in the first group.
If they were bed crocked good luck........jim

 

[fdshuster]

Tod: Like others here, I also do my scope leveling at the range, using a carpenters level for the top edge of the paper target, for the horizontal, and also hang a plumb line for the vertical.

It's also a good idea to check the benchtop for level, some are not, and of course, verify that the front rest is level.

As mentioned by K22, I also tighten the scope ring screws in the "X" pattern, and I also keep the gaps between the top and bottom rings all the same. An inch pound torque wrench is used (Borka) to properly set the ring screw tension.

 

[jonbearman]

How many inch pounds do you tighten those screws to if I may ask please?

 

[fdshuster]

jon: Contrary to the advice from Burris, I'm using 15 inch pounds as shown on the Borka tool.

For my use with the light recoiling benchrest cartridges, plenty. Even with my 308 barrel installed on one of the bench rifles, with a muzzle brake, 15 inch pounds has never been a problem.

All rings are the Signature Zee's, and another advantage I see with the Signatures: the nylon inserts grip the scope tube securely with less screw (T-15) tension.

When I contacted Burris Customer Service several years ago they recommended 20 inch pounds for the ring screws and 32 for the base mount cross-bolt. I'm sure that's good advice considering some of the really heavy recoiling cartridges that are out there.

 

[johara1]

If you don't shoot it you will never know if it tracks up and down perfect. It also tells you if your scope is working. This why you draw a vertical line and a plum does stay a little.....jim

 

[BoydAllen]

If you do a Google image search after copying and pasting this into the search window (or just typing it in)

Vertical Reticle Instrument

you will see many pictures of a device that Brownells sells. I think that it is the best way to get the center of a scope over the center of a barre, so that you can roll the scope so that the vertical cross hair is parallel with a plumb line. The only other thing that needs to be done beyond this is to post a tall target and shoot a number of shots at the same spot at the bottom of a truly vertical line, while raising the point of impact with the turret, to see if your scopes turret adjustments are in line with the reticle. They may not be. Obviously, this is all a waste if you do not refer to some sort of bubble level (that is alighned with your horizontal cross hair) when lining up a shot.

 

[johara1]

Donovan, that will work, but the level i refer to is a Starrett 98z,I think it acc. to .005 per foot.We are on the same page.I use a horizontal line also, a couple don't have a vertical wire. Both ways work,you are one of the few that put that much effort it set up a scope.It is the little things that count..........jim

 

[fr3db3ar]

I use a level on the gun just like you do. I set up where I can have a perfectly vertical point out in the distance (50 or 100 yards doesn't really matter) and align my vertical crosshair with this.

This seems to work for me but then again I don't YET shoot out to 1K like the big boys.

 

[BoydAllen]

For fixed distance target work, where there is time for a little adjustment for each distance, one can eyeball a scope close enough so that it will work just fine. I have done if for years. But if you want something that is more geometrically correct so that long shots can be taken with more confidence, at a variety of distances, where the first shot is very important, a more precise method is appropriate. An important part of this type of setup is having a way to accurately hold the rifle so that the center of the scope is on a plumb line with the center of the bore. As far as I know, there is only one tool that does this, the on e that I mentioned in my earlier post. Rings can bee offset slightly. Base mounting holes on factory actions are not known for the accuracy of their placement, and so forth. Also, none of this does much good if the rifle is canted as it is fired, so some sort of reference is needed on the rifle, that can be referred to when setting up the rifle for a shot. Of course this sort of thing is totally unnecessary for big game shots at typical distances. Deer and Elk are large targets compared to squirrels and prairie dogs. On the other hand, for those that like to work at long range, I think that having the best possible scope set up is important.

 

[4xforfun]

Well, been watching this thread for a few days now.....looks like NOBODY recommends my method.....good to know. As far as the scope, it is an older NSX that I have had for six years, so I know that it tracks strait up. The problem I have is my range....the ONLY distance I have had available to me all summer, and for the next month, is 750 yards. So there Will be no plumb-bobbing and string hanging in the near future. At least not till the crop is off.

Thanks, Tod

 

[AcurC]

This is the most precise way to align a rifle and scope.

https://www.youtube.com/channel/UCrUdPJToKibHd22VYb7yavA

 

[bugman]

Since you state this POI movement to the right is greater as the distance increases, have you considered this "problem" to be nothing more than spin-drift?

Jack

 

[CatShooter]

You must have a level on the rifle, and make sure that it is plumb when firing - if not, all the leveling of the scope is a waste of time, because the whole rifle can have cant at the time of firing.

It is not much of an issue when shooting 3" flat bottomed rifles with sighting shots to get "on", but in the field, it is critical.

 

[roadkill61]

For remingtons slide a piece of 3/4 " wide metal into the rear of the action along the bolt races. Put your accuarate level on this to level your gun. Then keeping the gun held tight sight the scope on a "plume line" and adjust. I line drawn on a piece of paper with a carpenders level is just asking for trouble. Been there done that .

 

[gmorganal]

I second the use of a feeler gauge. This usually requires a Picatinny rail setup.

 

[Nvreloader]

Go to Hollands Gunsmithing site, Articule section, look here: http://www.hollandguns.com/articles/Reticle.pdf

Does make a difference, at long range shooting.

Tia,
Don