Drilling a rifle barrel for sight(s)
How do you guys locate the holes for sights on a rifle barrel? I have done a few and have located the holes (top dead center) by eye and have been mostly lucky, until this last time. In the past, I clamped the receiver on one drill press and rest the barrel end in a V block on another drill press and then sight down the top of the barrel until it looks good and then drill and tap. This time I tried to do it on my mill but my shop is a bit cramped and I can't sight down the barrel as I have in the past. I used a small end mill and just kissed the top of the barrel and then drilled in the flat spot but it is slightly off causing the sight to look like it is leaning. So I am going to fill the hole with red loctited filler screw and then redrill right close the previous misplaced hole. I think I saw an interesting trick to do this once but can't remember where or hwo it was done. Thanks for any tips!
I haven't done one, but I would clamp the barrel in a mill vise with a v-block and edge find one side, set 0, edge find other side, split the difference and there you have the middle.
Either use a caliper to find the OD at that point then edge finders and a mill, or use a Forester jig on a drill press.
Universal Sight Mounting Fixture
The Forester jig contains bushings to guide drill bits and hold them centered without wandering.
OK. Its not a big deal ***DON'T*** re-drill and tap if you can. If it leans before 12 O'clock you can tweak the barrel tighter 1 or two degree if you have a proper barrel vise and wrench. It wont affect headspace noticeably. If its after 12 try putting paper shim's under it and see if it looks OK. If it does, use a ball mill or invert the site and use a fly cutter to take light cuts off the opposing side, or use a half round file to tip the site back straight. DON'T DRILL A BUNCH OF HOLES IN IT. In the future buy a sit jig or make one. The Forester is the best and its actually to short but its all that's available. Then work as follows.
(1) Clamp the barrel of the gun, complete in a padded vise on the mill and level by eye using the complete gun as reference.
(2) Install a weaver or other flat scope base to level off of and use a machine level to note the level.
(2) Set the barrel up on V blocks in the mill and use the pre-established level to go by. Always second or third guess what you are doing and eye ball it again. If it does not look right go through the procedure again. Always trust your eye when installing sights not the measurements. If the measurements are right its perfect but always double check with your eyes. Nothing on guns is straight or parallel.
(3) Best bet is to buy a forester jig and do what I have outlined for the mill. Even the Forester does not guaranty results.
What ever you do don't panic and drill a bunch of holes. Kids do that. Its going to cost you some time. Just fix it, buy the proper tooling and think about what your doing and don't do it again. Always remember NOTHING on a gun is straight, square or parallel! Because in most cases, idiots, lawyers, engineers and machinists make guns. Not gunsmiths. Always trust your eyes over the complete gun and not just a few parts. Installing barrels or making receivers or barrels from scratch is child's play because its all simple math and machining. Making stocks or installing sights is artsy/fartsy crap and requires a certain madness. For the most part it does not come with numbers to go by.
Thanks for the replies. I think I will drag the hole in the sight ramp/base and shim the opposite side to get it to the top of the barrel. The ramp/base uses two screws and I haven't drilled the rear one yet. The dragged hole in the ramp/base will be covered by the sight blade and the rear screw hole can be located correctly once the ramp/base is positioned where it is supposed to be.