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spindle valve question

This is a discussion on spindle valve question within the Gunsmithing forums, part of the M14 M1A Forum category; I'm getting close to being ready to assemble my first M1A (as soon as I buy or make a receiver wrench). I've purchased a NOS ...


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Old April 3rd, 2012, 06:43 AM   #1
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spindle valve question

I'm getting close to being ready to assemble my first M1A (as soon as I buy or make a receiver wrench). I've purchased a NOS (I think) unitized GI gas cylinder for this build. Since I haven't done this before I was hoping that you guys could give a little explaination on what the function of the spindle valve is, is there anything I should do to prep it for trouble free operation? I see that, as I received it, there is no roll pin retaining it in my GC, but when I tap it it doesn't want to come out. I'm wondering if that could be due to being heated when the welding was done to unitize the GC?

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Old April 3rd, 2012, 07:18 AM   #2
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If your GC was unitized by the screw and glue method, the screws are threaded INTO the spindle valve, so it WON'T move.

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Old April 3rd, 2012, 07:54 AM   #3
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The spindle valve allows gas to move from the barrel into the gas cylinder. It was originally used for rifle launched grenades so all the gas would be available to launch a grenade. When it's open gas moves to the piston, closed it all exits the barrel and you will have to manually cycle the oprod.

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Old April 3rd, 2012, 08:55 AM   #4
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My GC was unitized by welding the band to the GC. Looks to me like it was well executed. When I remove the piston, I can run a pin through the hole in the bottom of the GC all the way up into the bore that will slide over the barrel, so I'm assuming it's open. The slot in the head on the right side of the valve is oriented vertically. Would I be correct in assuming that if I just intall the missing roll pin I should be good to go?

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Old April 3rd, 2012, 09:10 AM   #5
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If you can do that, the it is open. The locking pin should run up and down, from 12 to 6.

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Old April 3rd, 2012, 10:49 AM   #6
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Thanks all for replies. Now I just have to aquire the receiver wrench.

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Old April 14th, 2012, 06:19 PM   #7
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Quote:
Originally Posted by Jgun View Post
I'm getting close to being ready to assemble my first M1A (as soon as I buy or make a receiver wrench). I've purchased a NOS (I think) unitized GI gas cylinder for this build. Since I haven't done this before I was hoping that you guys could give a little explaination on what the function of the spindle valve is, is there anything I should do to prep it for trouble free operation? I see that, as I received it, there is no roll pin retaining it in my GC, but when I tap it it doesn't want to come out. I'm wondering if that could be due to being heated when the welding was done to unitize the GC?
Barrel vise with inserts and Receiver wrench's are available from Brownells.com. When you buy the inserts, you actually get three since you have to contend with the classic M14 type barrel and the medium to heavy grade barrels currently made. I made my first Receiver wrench and vise (Vise was Walnut and bedded to fit). This is easier. Receiver wrench wasn't that hard, just time consuming. Vise was trickier. See the pic. Sorry but my receiver wrench is roughly 2600 miles away and I didn't take pictures of it yet.

Spindle valves were there for firing rifle grenades in one shot mode. I've tried to shoot the M14s and M1A with the spindle valve shut off so it was in essence a single shot rifle. Doesn't really add any accuracy to the rifle. This was back in 74 I think it was.

Since I've never seen the SAI "unitized" gas cylinder/front band, it may well be that they've cast the part as one or simply welded it, that I don't know. But if you go to the original USMTU guidelines for NM rifles, the way the front band and gas cylinder was drilled and tapped, made for a spindle valve that didn't work since the "long" screws would contact the valve. I don't unitize nor use "unitized" gas cylinders. Never need to. Don Stoehr taught me this 37 years ago. I have my own set of tricks and prefer to allow the barrel to free float as much as possible. Unitized gas cylinders do not allow a free floated barrel since they are tensioned by the stock ferrule and handguard which impedes the natural movement of the barrels. Go ask a good gunsmith if he has a good rifle and wants to accurized it, do they free float the barrel? I've had several good arguments about this one, but since I had Don sit me down and made me watch high speed film about the way the rifle and barrels work, I do it my way.
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Old April 14th, 2012, 06:23 PM   #8
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Hey Gus, I used to use crocus too, but try the Forster polishing cloth. See my private message, I can "arrange" that also. I recently tried it on a very screwed up SKS... I was surprised at how good it is..

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Old April 14th, 2012, 10:16 PM   #9
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IIRC, SAI has used different unitizing methods over the years.

My NM is "screwed'n'glued", so the valve is inoperable.

I seem to remember reading that they do dual-spot-weld unitizing nowadays.

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