I have a Chech Mauser 98 that i need to drill holes in for a scope/sight base. There are currently two holes drilled on the rear receiver for a redfield style rear sight base.

What I am looking to find out, is what drilling jig would work the best to drill the holes in the front receiver base?

I am thinking of using a one piece base. So far the most feasible ones I have found is the Ken Farrell one piece, or the Scott Medesha one piece. Dont know for sure that either will work yet.

I thought of attaching the base using the rear holes that are present, then marking the locations for the front screws. Is there a better way to determine/measure the proper distance on the firearm, in reference to the hole locations on the base?

Thanks for any suggestions.

I'm not that wild about any of the drilling fixtures. The B-Square or Midway type receiver drill fixtures are probably not going to work for you with a one piece base because you are wanting to locate the base using the existing rear bridge holes. The chances of the the front holes aligning between the jig and the base are pretty slim. Forster makes one that would work but you won't like the price of it just to drill and tap two holes. You'll also need to be sure that your holes in the front ring don't come through in a bad spot, like the face of the lug seat.

Why not use a more conventional scope base like the Redfield Jr. style? They're made by Redfield & Leupold. Leupold and Burris make nice looking two piece ones that may work. I'm assuming that the two holes you already have will work, but that's a big assumption for both of us to make.

Reason for a one piece rail base is this gun is a target style rifle and I want the option to swap between scope and irons. I am thinking a rail type base is the only way to accomplish this.

257,

You asked for suggestions, here's mine-

Like Mr Purcell, I would not buy a jig for this.

Like you, I like 1 piece bases for certain applications so what I would do is find a base you like and lay out the hole spacing on your action using as much care as you can. Do not use the rear base holes as a guide because if one of them is off center your making more work for yourself.

If you are planning on using a drill press to make your holes, I would suggest a good way is to make a base out of oak that your action is bolted to (dado out a groove in a block, bed with bondo, and bolt from the underside).

Combine a base like that with good layout and clamped to a drill press table and you have an easy, accurate job.

When you lay out your holes use a carbide burr to cut through the case hardening.

I would mount the rear holes, center punch the fronts to locate the holes, then use the B-Square jig drill bushings to guide the holes. I would skip the one piece unless you need a forward cant for long range shooting. Look at detachable bases for your setup, they will be lower profile and you won't need tools to attach/remove your scope.

John

Brownells has a Redfield International style iron sight adapter that clamps to a Weaver/Picatinny scope base that I used on a 223 target rifle-great for switching to irons from scope.

I've never had or used a fixture. When I first started doing this, I had a drill press with a cheap X, Y adjustable table and a machine vise. I would hold the scope base in place on the receiver using parallel clamps. After tightening the clamps I would verify that the base was square to the action by placing my calipers across the flats on the top of the base and the bottom of the receiver. It's real easy to see when your out of square using calipers.

Next I would take a drill bit with a shank diameter that would just barely fit through the hole in the base, and insert it upside down in the chuck, and then using the X, Y adjustments, move the "levelled" receiver under the quill until the shank of the drill bit would enter the hole I wanted to drill. Then I would swap the drill bit for the appropriate sized center drill and spot the hole. Then I would drill and tap the hole before moving on to repeat the process on the next hole and so on.

I never had any problems keeping the base square and the holes aligned using this method. Today I use my milling machine to do the job and rather than using the parallel clamps and the actual base, I zero the mill to the center of the bolt tunnel and transpose the hole spacing from the base to the top of the receiver using the precision dials on the mill.

Whatever you do, DON'T drill into the lug surface in the front ring. Most common problems with drilling Mausers is either getting them crooked or the rear hole on the front ring too far back. This puts a divot in the surface the bolt lug bears against.

Wespac gives good advice. I also did it this way when I started but now use the mill. Try a one piece Leupold or Redfield base and use the rear holes to check where the front ones will go and if it looks ok then just use that for a template using Westpac's method for checking level.

quote:

Originally posted by gunmaker:
Whatever you do, DON'T drill into the lug surface in the front ring. Most common problems with drilling Mausers is either getting them crooked or the rear hole on the front ring too far back. This puts a divot in the surface the bolt lug bears against.

Just out of pure ignorance,
What is the problem in having a divot in the surface percicely where the lug is split anyway, when the bolt is closed.

I often wonder,
Why is it ok to remove supporting material behind the lower lug, when opening up a m98 action to 375, when it is a big problem loosing unused surface on the upper support aerea. Here there is almost 3 times more supporting material than in the lower support aerea, even before opening up the ramp.
All this together with the fact that the lover lug is the unsplit, and strongest

I have drilled and tapped dozens of Mausers and have few of the Farrell one piece mounts from when Midway sold them for $20.

The difference between the front and rear mount heights are:
1) The Farrell single piece mount is .157".
2) Steel Warner Weaver style: .166"
3) Weaver #46 #45: .173"

I don't recommend that one piece, as it is too hard to get ammo in and out and adds 6 ounces in weight. I typically pay $10/ounce for parts that will lighten a Mauser. That means the Farrel mount not only costs $60, but adds another $60 in weight = $120 cost.

But if you must, you can see that it will require the shimming and glass bedding to the receiver that any two piece mount would, but the mount alignment is done, and bore alignment is easy.

I like to get all my Mausers with scope mounts the same distance apart, so scopes with rings will swap extra quickly.
For this reason, if it were my Mauser, I would put the drill and tap fixture on the receiver.


OK, I just went and got a Ferrel Mount and put it on a Wheeler Engineering drill and tap fixture. The Farrel has two holes in the front and one in the rear. This lines up with the two in the front of the Wheeler and the forward screw hole in the rear bridge area of the Wheeler.

What does it all mean?
Go ahead, it's your gun.
If you think mounts fit, you need glasses.