Gunsmithing Scope Installation... opinions needed.

[new_guy]

I always square my scopes to the bore (typically off the bases).

As I was installing the scope on this action, however, I noticed that the base is not square to the raceway cuts...

So... which way would you go?

Square the scope to the rail or the raceways of the action?

 

[GasLight]

Re: Scope Installation... opinions needed.

I would level the scope to perpendicular to the bore, I think this would be better achieved by leveling to the raceways. The scope base screw holes can, and likely in your case are, be drilled off center.

Dave

 

[Spuhr]

Re: Scope Installation... opinions needed.

As something definitely is crocked I belive you have a good reason to bed your rail.

Håkan

 

[flyrodder]

Re: Scope Installation... opinions needed.

I agree with GasLight's suggestion. You want the scope centered over the axis of the bore and the crosshair perpendicular to it. The raceways are more likely to be centered on the bore.

 

[300sniper]

Re: Scope Installation... opinions needed.

the raceway isn't doing anything other than giving a place for the bolt lugs to go when operating the action. i wouldn't put too much thought into where it is in relation to your scope base/scope. there is nothing saying the raceway is at a perfect 90* to the rest of the rifle.

there are too many variables with a factory action to assume anything is in line with anything else. this is the reason i simply use the feeler gauge/shim method to mount scopes.

unless you fully true the factory action based on the bore centerline, use a mandrel to find the absolute center line of the receiver, use the raceway to level the rotation of the receiver and then re-machine (not chase with a drill) the scope base holes and the trigger guard screw holes, you are not going to be perfect.

 

[GasLight]

Re: Scope Installation... opinions needed.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Spuhr</div><div class="ubbcode-body">As something definitely is crocked I belive you have a good reason to bed your rail.

Håkan</div></div>

^^This^^

if the base is far enough off, it will be impossible for the vertical crosshair to bisect the bore, which will result in some kind of error at distance. The ideal solution here is to have someone (preferably competent) enlarge the holes to 8-40 and make sure they are centered to the bore... Bedding the base will help if it isn't too far off, or if the holes are on center but drilled in crooked.

 

[Clark]

Re: Scope Installation... opinions needed.

There are competition guns with the scope canted.

It does not make any difference if the scope is straight up.

But you do want the cross hairs plumb with gravity, so the scope should jive with a the level, if your rifle has a level.

Otherwise, sight in with cross hairs right with the horizon and then shoot with the cross hairs right with the horizon.

 

[Hellbender]

Re: Scope Installation... opinions needed.

Get a straightedge (the beam of a caliper works well) and lay it on top of your rail, hold it up to the light and see if the base is flat.

If it's not (probably), then bed the base flat and true. Mount the scope with the feeler gauge method (square to base) and shoot it.