Unitizing the gas system on an M1a

[sacp81170a]

I've been searching for instructions on unitizing the gas system on my SA M1a with screws or by welding. I've seen a few pictures, but no instructions on where to drill and tap or spot weld anywhere. Does anyone have detailed instructions?

 

[Telperion]

Pick up a copy of The M14 Owner's Guide by Scott Duff and John Miller. There is a chapter on match conditioning and it describes both methods in detail. I don't have the Kuhnhausen book, but that might also be a place to check too.

 

[sacp81170a]

Thanks!

 

[Slamfire]

I recommend finding someone who knows something about welding.

I had a high school shop teacher weld a couple of gas cylinders to the front band. He talked about the proper weld material he had to use (not too hard, not too soft) and it just takes a tiny tack weld so things don't get hot.

The screws method was a specific method used by the AMU types, based on the shop equipment they had at the time the methods were documented. It is not the best way. It was just a way.

I have had the bloody screws come loose, and blow the best darn Leg score I had to six hundred. I was down less than five points (I know I had shot a 99 standing, probably shot 99's or 98's in the rapids) and then my rifle started flinging shots at 600 yards. I found that the screws to the front band were loose, and that the op rod guide was loose.

I had a Springfield Armory barrel, and they were not pinning their op rod guides. Well I drilled and pinned the one on the rifle. And it stayed put till that barrel was replaced.

What I learned, is that gas blowing through and around the spindle will loosen up those screws.

So I had the front band tack welded to the gas cylinder. And it is still fixed.

 

[For Freedom]

SAI will do it for $35.

 

[Beagle-zebub]

Was this a problem on issue M14s?

 

[mtgale00]

Was this a problem on issue M14s?

No. It is one of the steps for accurizing an M1A/M14.

 

[For Freedom]

 

[Beagle-zebub]

So this gas-block is not a standard item, but rather something you put on for the sake of accurization? If that's what it is, what about the original leads to inaccuracy?

 

[sacp81170a]

If that's what it is, what about the original leads to inaccuracy?

The front band is what holds the barrel and gas system in the front of the stock. If it has room to wiggle around, it changes the barrel harmonics slightly with each shot. It's not that big of a deal if you're looking for minute of bad guy accuracy, it is a big deal if you're looking for MOA accuracy.

 

[Onmilo]

You have to epoxy the screws in place or tack weld the screw heads and grind the weld flush or the screws will come loose.

One advantage to welding, if it is done properly, is that you can still use the spindle valve.
Screw unitizing locks the spindle valve.

One big disadvantage to welding, if it is not done correctly, is heat warping the gas cylinder.
If this happens the gas cylinder is trashed.

 

[madcratebuilder]

Get the Jerry Kuhnhausen book. Everything you need to diy your M1A. Both 'screw n' glue' and 'tig weld' work and both have been know to fail in the field, the screw n' glue is repairable in the field. Some pass on the unitizing and just shim the gb. Other do both. I'm in the both camp.

 

[H2O MAN]

I have one screw-n-glue, two that are shimmed and two with SAGE washers.
The screw-n-glue is in my parts box, the other four are on grab-n-go rifles.

 

[30Cal]

I'd recommend buying one or having someone that does it for a living do the work. There is some fixturing involved with either method (a modified section from a dead barrel).

If the two parts aren't concentric, either the rifle will need to be bedded askew or the stock ferrule will get mauled in short order from uneven contact with the barrel band.

 

[For Freedom]

I kind of wish I hadn't gotten the SAI one for my Standard. It was really tough to install. Perhaps I should have checked it for burrs before hammering it on.

So with the SAGE, do you get washers or shims since the front band isn't there anymore?

 

[H2O MAN]

For Freedom

So with the SAGE, do you get washers or shims since the front band isn't there anymore?

Correct.
SAGE supplies 3 washers of different thickness. Here is a close-up of the one on my MK14 SEI Mod 1
The set-up is rock solid

 

[For Freedom]

Nothing to be unitized there! Looks great!

 

[Jenrick]

H20Man, you mind posting a pic of the whole rifle? A buddy at work just bought a SOCOM, and now my M1A craving is in full bore again. Got to figure out what to save up for, cause this time I AM buying an M1A

-Jenrick

 

[30Cal]

I kind of wish I hadn't gotten the SAI one for my Standard. It was really tough to install. Perhaps I should have checked it for burrs before hammering it on.

It's supposed to be a very tight interference fit. Anti-seize is highly recommended and if you're not using a mallet to drive it in place, then it's probably not tight enough.