I've just purchased an older German scope that has the mounting rails attached to the bottom.

The rifle I want to put it on has claw type mounts and has the same type scope currently on it and in the claw type mounts.

I want to switch out the scopes. The claw mounts attach in a way that the rail on the scope has to have holes drilled in it that line up with the screws on the claw mount bases.

The new scope has holes drilled in the rail but they do not line up with the claw mounts on the rifle so the rail on the new scope has to have new holes drilled in it.

Is this something most gunsmiths can do or do I need to have someone who specializes in this work?

Drilling straight through a prismatic shaped rail is best left to a pro. Other than that, there is no problem to have new holes drilled in the right place in order to mount the scope. I've done it after having a second hand scope installed on this Mauser 66 rifle. As a finishing touch, I filled the old holes level with steel putty and when dry, I touched it up with black enamel (the kind you paint scale models with). One needs a magnifying glass to notice the repair.

Most local "gunsmiths" cannot do this work, or much of anything except replace parts. You need to get to know what they are capable of. We have several hacks around here to whom I would not trust with anything.

For a second I thought someone may have said that evil "DRILL" word. A lot of the time it's not a hole that you're after but a slot. Well, sometimes a hole. Drills have a nasty habit of going in where they are supposed to, but coming out in a not-so-much-supposed-to spot. I gave up the evil "D" thingy many years ago and started using carbide slot mills for the task. 3mm is the most common size. I run them just a tiny bit short of ludicrous speed and bordering on insane speed. Kerosene is your friend in most cases too!


3mm slot mill by Rod Henrickson, on Flickr

Yeah, That's the system that I was referring to Duane. Most of the time the hole in the base (female) part is already established and a half moon cut, or sometimes full hole, has to be drilled through the male portion which is affixed to the scope. I have seen uncounted numbers of guys drill them, but the drill starts to wander the instant it hits the angle on the scope dovetail. If it happens to require a half moon on the scopes dovetail the drill can also begin to wander toward the base as soon as it starts to cut the half moon on the scope dovetail. I won't say hundreds, but I have seen more tapered half moon slots on the bottoms of high end scope rails than I could ever care to count and just as many egg-shaped holes in the base's.

I have also seen a lot people cheat and use ball mills to simply cut slots EXTRA LARGE, in the base of the scope because they couldn't get them exactly marked or measured to make the half moon cut on the scope in the correct spot or didn't have the means to setup the entire gun in the mill to cut the two parts together. It works but it defeats the purpose of having the screw as a recoil stop and the front base or ring generally has to take the brunt of the force instead of spreading it evenly between the two bases.

I always try to clamp the whole affair together, set it up in the mill and pass the slot mill through both parts at the same time if I can. If I'm uncertain about the absolute level, I will cut half way through and then flip the gun over and cut the other half from the other side just to be 100% certain that it is cosmetically correct. Light polishing in the half moon slots will blend where the two holes meet if there is a slight discrepancy.

In addition to my 1st post, I own several examples of rail scopes (Sühler claw mount or swing-out) were holes had to be drilled through the scope rail. In every case, the (experienced) gunsmith used a special fixture (kind of an adjustable bracket) to hold the scope in place and prevent its shifting during the drilling operation. Here are some more pics :


Chapuis Super Orion o/u in 9,7x74R + Sühler claw mount.


FN-Browning CCS o/u in 9,7x74R + Sühler claw mount.


Detail of claw mount (hand fitted) on former FN double rifle.


Blaser R93 .300 Win Mag with (drilled) rail mount (older type).


Blaser R93 9,3x62 with present no-drill type rail mount.


Sauer 202 .30-06 + EAW swing-out mount and drilled rail scope.


Customized Win 70 .338 Win Mag (Lothar Walther bbl.) + fixed EAW mount and drilled rail scope.

NB : the present new type of rail (Swarovski, Zeiss,...) does no longer require drilling and I was able to install this 1,25-4x24 scope on a Blaser mount myself. Cf. above pic of R93 in 9,3x62).