Blueprints for M14 NM Sight Base

[Danny]

Does anyone have any kind of a blueprint for the USGI NM Rear Sight base? I'm going to cut one of my USGI Issue Sight Bases to accept the hooded National Match Apertures, and it might as well be the USGI Dimension, not the dimension that I've found on the various Repro Sight sets, including the SA Inc. ball detent sights. I need to find out how much to mill the cut in the base to accept the hood properly. What I don't want is for someone to go out and measure their rear sight base,which is probably one of the above types of sights, but I'm sure that someone is still going to do that, even after I add this disclaimer. I can do that myself, yet I'm still posting a question on this.


Danny

[cruiserdan]

After all that work you will still have a 32 TPI windage knob thread. Unless you intend to drill the receiver for the ball bearing mod I don't think you have gained all that much.

I have used a hooded aperature in a standard base before and I have not had a problem where I could not lower the sight far enough for short range.

I wish I could help with a design blueprint.

[John Kepler]

Huh? NOTHING is required for a standard base to accept a hooded aperture....not a blessed thing! You'll still only have the 32 tpi in the windage adjust, but the 1/2 moa hood will fit just fine.

[BDH]

http://www.milsurps.com/images/imported/2009/03/standard-36.jpg

Found this pic I downloaded some time back. The cut is about .310 from the bottom of the base to the bottom of the radius. The width of the cut is ~1/2", allowing the hooded sight to sit lower in the base.

Taken from a NM/2A base installed on an M14.

HTH

Bruce

[Danny]

I should have the drawings coming my way soon. If and when I get them, I'll post any of the dimensions that look helpful.

Danny

[Tom in N.J.]

I would have lost money on a bet!.. I believed only the windage knob threads were different from a standard M14 rear sight base. But on looking it up, I find two NM sight bases listed, 7791341 (1005-875-6281) which IS noted as being undercut for hood aperture. It is to be marked NM/2. The other is 7791571 to be marked NM/2A.

[cruiserdan]

Both the /2 and the /2A are undercut.

The very early NM base, marked simply "NM", has 64 TPI for the windage knob but is not indercut for the hooded aperature. The early NM aperatures looked like battle sights but with either a 520 or a 595 hole.

[Danny]

Ok, I've gotten the drawiings for the issue sight and the NM2/A (part #7791571). On the issue sight, the distance from the bottom of the .500" clearance cut to the bottom rear edge of the sight base is .425" -.010" and on the NM/2A sight, the dimension for the same is .365" -.010". I'm going to check to see, just for curiosity if any of my Springfield Inc. NM Sight Bases or my fine thread NM Sight bases came close, and which is actually close to spec. I'll mill another issue sight base to those specs soon.

Danny