Never tried to do this myself..So I want to give it a try..I have a Navy arms 50-70 rifle nothing of great value so what the ****..It has an octagon barrel with big wide flats..I want to scope it.I plan on using a Weaver style base with at least four holes in it...How do I know what size tap and drill I will need to do this..I heard all I need is the bottom tap? Is this correct?

What size are the screws that come with the Weaver base? I think I am going to use the 63B style..I have a drill press and a vice to hold the rifle level..Any advice is appreciated...Thank you..John

The Weaver mounts use the 6/48 screws.

You can get the drills and taps from www.midwayusa.com (http://www.midwayusa.com) or www.brownells.com (http://www.brownells.com) in kit form. Get a careful scribe on the centerline of the barrel (the big, wide flats will be a great help here), centerpunch the holes and be very careful to level the barrel in the vice. Mark your drill bit with tape to assure you don't over drill. Remember to use plenty of oil with the tap (use a tap wrench - DO NOT chuck up in the press with the power on! You can get a wrench that will fit the press you can turn by hand, using the press handle for leverage - that helps keep the tap straight.) and only turn the tap clock wise.

One other suggestion to the fine directions given above is Brownells has drill bits with fairly flat bottoms that let you get the proper depth without the long point of most drill bits.

Thanks for the pointers...Is there a certain name for the blunter tip drill bits mentioned above? What size bit do I need for the 6x42 taps...

If you buy the drill/tap kit from Midway or Brownells, the 6x48 drill and tap come together. Wouldn't be a bad idea to get the 8x40 at the same time, as some heavy hitters need the larger screws. I never worried about the flat bottom drill bit - the tapered one works just fine.

This is what I found at Brownells...146"-48 X 1/2" "OVERSIZE" 6-48 SCREWS

Does it look right or do I ask for the 6x48 I noticed they also had the slotted head..Shouldn't I want to use allen head or socket heads...

A Weaver 63B should come with standard 6-48 screws. Mine's several years old and the screws are slotted. Use a fitted screw driver and you won't have problems.

Brownells tap numbers are:
395-648-001 Taper
395-648-002 Plug
395-648-003 Bottoming
Use a 31 drill

Check out this thread for tips on tapping. I'd suggest practicing on some thin mild steel, copper or aluminum before you do the gun. DON'T try going all the way in one pass or you'll break the tap. Take half a turn, back all the way out and clean out the swarf or it will jam the tap.

http://www.shootersforum.com/showthread.htm?t=23212

Bye
Jack

Very good and easy to understand directions...
I really appreciate you guys helping me out here....
I am getting ready to order from Brownells this
morning...I think I might order a few extra screws
I have a habit of loosing them..Thanks again..John

IIRC, the brownells oversize screws are designed for holes that were tapped poorly

JB12---Thanks for the information..I was wondering about that..

Well,I guess I got everything order to try my hand at the drilling and tapping.

Ordered from Midway...Drill-tap base scope and a new vice for my drill press..

Thanks again for all of your advice and suggestions...John

What I usually do is:

1. Locate holes.

2. Double check hole location and prick punch.

3. Center punch hole location.

4. Start hole with a center drill.

5. Drill with tap drill.

6. Tap hole using an alignment pin between drill chuck and tap wrench.

Repeat process for next hole. I always drill and tap one hole at a time. That way I can maintain tap alignment in drill press.

Just be sure the holes you drill are square with the barrel and not so much with just the action. A good drilling jig costs money, but it sets the action in a V section at the back, and the barrel sets in one, so that the barrel and action are centered together. Just gives you an idea that you see that your not just drilling to be square with the action only.