Smith Enterprises NM Rear sight install - Left over part!!!

[IC Phyer]

SA not SEI - Left over part - SOLVED!

So I was putting a NM Rear Sight on my SA M1A Loaded. Followed the dirctions in Kuleck/McKee's book, well lubed, full range elev. and wind, etc. Everything looked good, picked up the rifle, raised the muzzle, and a small ball bearing struck the back of my right hand right between the thumb and forefinger as I was gripping the stock as I normally would to fire the rifle. It seemed to fall directly out of the rear sight. I did not see it fall or strike my hand, but considering the location it hit my hand and the location of my hand on the stock, that's my best guess. Now I looked through Kuleck/McKee's book and I can't find any mention of a ball bearing in the rear sight in the text or the diagrams. Anyone know if there is a ball bearing(s) in the NM rear sight or in the M1A at all? The rifle seems to be operating fine, trigger safety check, cycling, etc. Any help would be appreciated. Could this be a loose bearing on my workbench getting into my rifle?! Thanks ahead, David

 

[mshootnit]

ball bearings are often used in conjunction with springs to create a detent mechanism. Wouldn't surprise me at all if it came from your sight. No first hand knowledge of the part however.

 

[DnPRK]

The M-1A uses a spring-loaded ball detent to secure the windage knob (similar to the AR-15/M-16 A2 windage knob). This is a design difference between the M-1A and the M-1 Garand and M-14. IMO, the ball detent windage knob works smoother than the belleville spring setup of the M-1 and M-14.

 

[IC Phyer]

This particular sight is not an SA M1A sight. The original sight was SA. This sight is a Smith Enterprises NM rear sight, the same sold by the CMP and used on the US Army DMR, according to the seller.

I should have mentioned this in my first post, apologies.

The windage adjustment is working with full range of movement and good detent stops and tension.

Anyone know if they have ball bearings? I'll contact Smith Ent. also. Thanks for your help.

 

[dmazur]

If this is an extremely small ball bearing, I may have had experience with these re: NM rear sights.

I found a diagram for one of these somewhere on-line, and it described the detent mechanism in the rear sight aperture. There are two small springs and two small ball bearings in holes. When you rotate the sight 180° for the 1/2MOA adjustment, these ball bearings "click" into shallow holes (or detents) on the sight.

The diagram notes went on to say "Do not attempt to disassemble the NM rear sight."

I had a bent "E-clip" and I thought I'd take it off, straighten it, and reinstall it. In the process, I dropped one of these cute little ball bearings, noticing it only after I reassembled it and saw the aperture was crooked. I should have looked up a diagram before disassembly.

It took a new vacuum bag and 15 minutes to find the thing in the carpeting, then I sorted it out of the dust bunnies with a magnet.

If you didn't lose yours in the carpet, you're probably lucky. As long as the little spring is still in its hole, you can probably reassemble it.

If the E-clip isn't bent, there isn't enough room for the ball bearings to fall out, so you may have something slightly out of true on your sight...

 

[IC Phyer]

The ball bearing is .125" (1/8") in diameter. The hooded aperture does not look crooked with the naked eye. How obvious was yours?

I did notice that it does not detent with the V-notch exactly up or down. It's off just a bit, but that is how the pic of hte hood on Smith Enterprises' sight is also so this may be normal.

It seems just a tad loose, and weaker detent stops while rotating, turns easier than another hooded aperture (not fitted) that I have. I do not know the brand of the second hooded aperature.

How easy was the hood to get apart and, more importantly, how easy was it to get it back together? Any special tools needed?

Thanks.

 

[madcratebuilder]

The ball bearing in the aperture is .062 I think. If your SA came with a SA NM rear sight it used the ball/spring as a detent and used a .125 ball. You would have a .125 blind hole on the right side of the receiver under the windage knob that held the spring/ball detent.

 

[IC Phyer]

The original SA sight was a 1/2 NM, ie. normal 1 moa elevation (no hood) and 1/2 moa windage.

I will check the right side receiver for a blind hole. Hopefully the spring is still in there!

 

[dmazur]

The one I had trouble with was one of the aperture ball bearings, 0.062" diam. The aperture definitely looked crooked with one of the bearings missing.

The NM sight I have doesn't have a 0.125" ball bearing that I'm aware of.

I don't have the history of the rifle, but it is a SA reproduction Garand with NM front and rear sights.

 

[IC Phyer]

DnPRK and madcratebuilder are spot on. The ball bearing came from the SA receiver and is for the windage detent. I found the blind hole and it looks like the spring is still in there. I will remove the SEI sight soon to get it, but right now I'm too busy shootin'!

The SEI sight is working perfectly.

Thanks everyone for your help.