Need help with some M14 information gathering

[DaveInGA]

Howdy all,

If you've got an M14 of any sort/brand with USGI sights and Chinese sights, I'm needing a measurement taken. On the windage knob, there's four nubs or engagement surfaces that slide against the receiver and lock into the slots on the receiver that form an "X" on the right side of the receiver.

I have a theory they are slightly longer than the same part on an M1 Garand windage knob, but am looking for confirmation and I don't have a USGI M14 windage knob to measure. I have plenty of M1 Garand windage knobs. In this case, I'm only looking at standard sights, not National Match sights.

So, if you have a USGI M14 windage knob, USGI, Polytech or Norinco, would you measure the length of those four nubs/engagement surfaces for me and post the results?

Thank you,

Dave

 

[Pr589]

Dave,

These measurements are from a Norinco sight. The nubs I measured are raised surfaces at the 3, 6, 9 and 12 o'clock positions on the windage knob. The are a little hard to measure since they have sloped sides. That said, the top surface seems to be 0.13" long and the base seems to be 0.19" long.

Hope this helps.

 

[DaveInGA]

Dave,

These measurements are from a Norinco sight. The nubs I measured are raised surfaces at the 3, 6, 9 and 12 o'clock positions on the windage knob. The are a little hard to measure since they have sloped sides. That said, the top surface seems to be 0.13" long and the base seems to be 0.19" long.

Hope this helps.

It does, would you be kind enough to measure the width of the "X" slots on the receiver as well?

I have an older Polytech M14S, s/n 21### and the same measurements seem to be 0.16" long at the top and 0.23" at the base for the windage knob.

I also grabbed a Italian (Beretta made) USGI surplus sight assembly I have and measured it. the nubs are 0.153" at the top, with a long slow leading slope and a steep following slope and measuring 0.164" at the base nub.

The specification for the slot of the "X" is 0.160" +/- 0.008." My Polytech slot measures 0.174" at the bottom of the slot or about 0.006" over the maximum specification.

I'm now wondering if the older chinese rifles or just the older Polytechs had/have wider slots. Mine has been in the U.S. a long time. From Lee Emerson book, the receiver was manufactured between 1988 and 1993. The rifle was sold here in the US between December 1993 and February 1994.

What I'm seeing here is with the receiver being over the maximum specification and a Beretta windage knob being narrow, there is definitely some tolerance stacking to the point this Italian USGI windage knob would have slop/hysteresis if used on this rifle.

 

[DaveInGA]

Found a resolution to the issue. Received a windage knob for a BM59 rifle today. The bosses on it were as wide as the original polytech windage knob, so fit the receiver well. They also fit the Beretta M1 rear sight assembly I had put on. Issue resolved and now windage knob slop/hysteresis feels about the same as my 1950's built M1 rifle.

 

[sunray]

What's the purpose of the measurements? Just curious. Not at home, so I can't measure my Winchester M-14 or my Springfield M1 sights.
M1 Rifle sights are graduated in yards. M-14, that you don't have, sights are graduated in meters. So they're different anyway.

 

[45ACPKING]

Yup, that's why I prefer genuine GI m14 sight sets and I especially like those BM59 rears for my 18.5" barrelled rifles
M1 garand rear do work on a great many chinese receivers just fine, however, the problem Dave ran into is pretty common when you build a lot of these rifles.

 

[WetCoast]

Damn, Thomas, just received my front sight from SAI based on a recent comment of yours and was wondering which rear sight to get. PB BM59 from Treeline it is. Thanks for the info!

Yup, that's why I prefer genuine GI m14 sight sets and I especially like those BM59 rears for my 18.5" barrelled rifles
M1 garand rear do work on a great many chinese receivers just fine, however, the problem Dave ran into is pretty common when you build a lot of these rifles.

 

[DaveInGA]

Damn, Thomas, just received my front sight from SAI based on a recent comment of yours and was wondering which rear sight to get. PB BM59 from Treeline it is. Thanks for the info!

Based on my experience, I suggest you take a measurement of the windage slots in the receiver that form an X before you order your rear sight set. If you're out of spec on the large side, the BM59 sights will be great. If you're in specification, you won't need the BM59 and can use any other USGI rear sight assembly.

BTW, the rest of my rear sight assembly was all Beretta. Compared them to USGI and they're very finely made, especially the peep, the windage and elevation knobs. Went together and adjusted easily on the chinese receiver.

 

[WetCoast]

Thanks Dave, you were right about the size of the windage slots. Mine seem to be even larger than the ones you measured and there is a tiny bit of slop on the windage slots even with the BM59 sight. Nothing catastrophic though. The aperture on my the peep is quite a bit smaller than the Norc one. Strangely, this seems more intuitive.

And you were absolutely right about the quality of the PB sights. As nice as the USGI on my Garand. The PB from Treeline were basically like new! None of the rough feeling of the Norc sights and aesthetically no comparison. Thanks again for the advice. If you hadn't asked your original question I most certainly would have purchased the wrong sights.

Based on my experience, I suggest you take a measurement of the windage slots in the receiver that form an X before you order your rear sight set. If you're out of spec on the large side, the BM59 sights will be great. If you're in specification, you won't need the BM59 and can use any other USGI rear sight assembly.

BTW, the rest of my rear sight assembly was all Beretta. Compared them to USGI and they're very finely made, especially the peep, the windage and elevation knobs. Went together and adjusted easily on the chinese receiver.