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I know how gas cylinders are unitized and I know this may start a fight (Art and Huey Gunner be nice) but what are the advantages and disadvantages of the different techniques. Is there an inherent accuracy difference to either?
 

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One of the things is you loose the use of the spindle valve when you screw and glue. With the weld method you don't. Other than that I haven't heard much about any difference.
 

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I've had both and like the weld method better. It's nice to be able to shut off the spindle valve when cleaning. I recommend also using shims with either method if the unit doesn't lock up tight on the barrel shoulder. This will help reduce the chance of the welds breaking or screws backing out as well as reducing stress on the gas lock and plug.
 

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I also like the welded method because of the spindle situation. It's convenient for cleaning and I sometimes cut it off at the range for certain reasons like trouble shooting for accuracy etc.
 

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Unitized Gas Systems

I know how gas cylinders are unitized and I know this may start a fight (Art and Huey Gunner be nice) but what are the advantages and disadvantages of the different techniques. Is there an inherent accuracy difference to either?

There is evidence the Unitized Gas System produces better accuracy. It is important to put that statement into context. All the Modifications to the M14 NM rifles were for the purpose of producing the most accurate "Across the Course Rifles"... Across the Course accuracy is a specific Match Competition requirement. Accuracy desired or needed in a M1A, modified for General accuracy such as Bench Rest shooting, long range prone position shooting is another matter. This, of course is yet another opinion, but there is just as much evidence to support it..

The Across the Course Rifle takes more abuse than the General Accuracy Rifle, much more abuse. Therefore the Gas System must be Unitized in a stronger method, using screws, welding, epoxy or all of those. The General Accuracy Rifle, which I think most of us have or want does not require this type of Unitizing. The proper selection of shim/shims and a high grade epoxy will do a perfectly sound job of holding the Front Band and Gas Cylinder together..

You are the decision maker in which method of Unitizing is best for you... A good place to start your decision is by asking yourself, "How do I intent to use my Rifle?"

I may as well add, The Not Necessary requirement of Reaming of the Flash Suppressor to the above if you are seeking a General Accuracy M1A. There is no evidence to my knowledge that reaming the FS adds accuacy over a properly installed non reamed FS, unless of course you intend to shoot in a down pour. How many of you M1A owners even take your rifles our when there is heavy fog?

When the Service Shooting Teams went to the Reamed FS it was for the purpose of avoiding the problem of a FS being accidentally knocked out of alignment, this information was according to Sgt. Bill Donovan USMC. He told me,"In addition to reaming, the muzzle seating surface was resurfaced to promote a flush seat against the end of the barrel, if accuracy improved it was more likely because of this modification than the #7 tapered reaming." There were several more modifications done to the FS at that time, as I recall there were five {5** lathe cuts made not of importance in this message.

Allow me add, I have seen Hueygunner's work, he is Craftsman, he would be my choice if Unitizing was desired. I have not seen the work of the others that do this modification. it is not my practice to recommend something I have not seen or tested.

Is this a statement of De- hyping unnecessary modifications, not at all, but rather a History Lesson you can accept or not. Art
 

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Why do you lose the spindle valve function with the screw/glue method? Is that what sai uses for theirs?****Teds post below explained the spindle valve issue***
 

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Unitizing

I've written reams about this subject, but it continues to come up and deserves attention.

Art makes many good points, but we don't always agree on everything. It's probably safe to say no two armorers do. Across the course guns do require specific modifications to hold up under the rigorous conditions of National match shooting. Where I differ is that I believe any M14 that requires accuracy modification for any kind of precision shooting benefits from these same modifications.

Flash suppressor reaming was proven to increase accuracy by the USAMTU early on. Not only for the rain problem and possible misalignment issues, but because the bullet is disturbed less by gas pressure as it enters the reamed flash suppressor.

Both welding and the screw and glue method of unitizing work well. The object is to prevent barrel band movement, insure consistant band to ferrule engagement, and thereby stabilize the barrel from all the effects of the many moving parts attached to it.

The downside of welding is that welds cannot be repaired in the field if they fracture, and they do from time to time. This is detrimental to accuracy. Besides, they are ugly.

The downside to the screwed and glued method is that the screws pass directly though the spindle valve which renders it non-adjustable. It's always going to be on and cannot be shut off. I don't know how serious this is since the only reason the valve was installed in the first place was to prevent damage from overpressure when launching grenades. In all the years I have been shooting M14 rifles, I think I have only shut the valve off once, just to see what it would be like. With sharper recoil and no significant increase in accuracy, I found shutting it off wasn't necessary.

The only possible failure to the screwed together system is that the screws may shoot loose if they are not proberly epoxied and staked in place. Of the hundreds of screwed together gas systems I have built none have been reported to have failed. I have seen a hand full of unitized gas cylinders with loose screws. I don't know who built them, but I know at least some were done by Army or National Guard armorers. The nice thing is that they were easily fixed with a screw driver until they could be reglued and staked back in the shop.

Unitizing does what it is supposed to do, but I should point out that it's benefit is minimal unless done in conjunction with glass bedding. Unitizing is only a small part of the accuracy equation.
 

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Art, Ted, WOW!!

Thanks for the great info and excellent descriptions.
 

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As we tear down GI rifles we find both methods of unititzing the gas system. On the ones that we have found to be welded, they also welded the spindle valve in the on position. Not sure if that was done here at Rock Island or somewhere else.ARMY1
 

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i personally prefer welds to screws, however both methods work. properly done, welds are nearly invisible, poorly done, welds are ugly. i dont bother with turning the gas valve off for cleaning, i turn the rifle upside down, as this keeps solvent out of the gas cylinder, and out of the bedding.
 

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I've written reams about this subject, but it continues to come up and deserves attention.

Art makes many good points, but we don't always agree on everything. It's probably safe to say no two armorers do. Across the course guns do require specific modifications to hold up under the rigorous conditions of National match shooting. Where I differ is that I believe any M14 that requires accuracy modification for any kind of precision shooting benefits from these same modifications.

Flash suppressor reaming was proven to increase accuracy by the USAMTU early on. Not only for the rain problem and possible misalignment issues, but because the bullet is disturbed less by gas pressure as it enters the reamed flash suppressor.

Both welding and the screw and glue method of unitizing work well. The object is to prevent barrel band movement, insure consistant band to ferrule engagement, and thereby stabilize the barrel from all the effects of the many moving parts attached to it.

The downside of welding is that welds cannot be repaired in the field if they fracture, and they do from time to time. This is detrimental to accuracy. Besides, they are ugly.

The downside to the screwed and glued method is that the screws pass directly though the spindle valve which renders it non-adjustable. It's always going to be on and cannot be shut off. I don't know how serious this is since the only reason the valve was installed in the first place was to prevent damage from overpressure when launching grenades. In all the years I have been shooting M14 rifles, I think I have only shut the valve off once, just to see what it would be like. With sharper recoil and no significant increase in accuracy, I found shutting it off wasn't necessary.

The only possible failure to the screwed together system is that the screws may shoot loose if they are not proberly epoxied and staked in place. Of the hundreds of screwed together gas systems I have built none have been reported to have failed. I have seen a hand full of unitized gas cylinders with loose screws. I don't know who built them, but I know at least some were done by Army or National Guard armorers. The nice thing is that they were easily fixed with a screw driver until they could be reglued and staked back in the shop.

Unitizing does what it is supposed to do, but I should point out that it's benefit is minimal unless done in conjunction with glass bedding. Unitizing is only a small part of the accuracy equation.
Ted , i have to disagree with you on one thing, about welds being ugly. You have not seen one of my welded cylindersGI2 IMO a properly done weld is a thing of beauty!
 

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I agree

Welds can be almost invisible. I was just being facetious (grin).
 

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Really, you may want to hold off deciding until the glass bedding is complete and you're down to perfecting front-end alignment. Screwed & glued works well if you need to scribe the front band to dial in a minor offset to get the desired contact with the stock ferrule on the particular rifle, which may sit well but not 100% level in the stock. But either way's fine if you're installing gas cyl + front band already unitized.
 

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Good stuff here..

Really, you may want to hold off deciding until the glass bedding is complete and you're down to perfecting front-end alignment. Screwed & glued works well if you need to scribe the front band to dial in a minor offset to get the desired contact with the stock ferrule on the particular rifle, which may sit well but not 100% level in the stock. But either way's fine if you're installing gas cyl + front band already unitized.
Off again on this front band alignment issue. This post is excellent.

If you desire to have a "perfect" Front Band Lip alignment to the Stock Ferrule there is little to no guarantee that this can be accomplished using a Unitized Gas System. The Gas System must be Unitized after the bedding procedure to get it perfect. The above is an opinion...

I'll have to leave Town soon after this statement. Art
 

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Hey Art...

Don't leave town just yet.

The bearing of the band on the ferrule is critical and often requires some adjustment during bedding and final assembly. There's a lot more to bedding than just routing and applying the epoxy.
 

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This post has been full of great info.
From the prospective of an XTC and LR competitor, I will throw in my 2 cents.

I have broken welded units and I had screwed and glued units come apart. I found a screwdriver much more field expedient than a TIG welder.

Occasionally, I find a reason to shut of the gas - I do not want to fetch my brass in the snow when function testing or doing the initial incremental load testing with a new barrel.

JW
 

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Just one of the variables

When a stock is routed for bedding we have to assume, to some degree, the vertical routing {plunging** is 90 degree to horizontal, and that the action will sit flush and 90 degrees to the horizontal. This is a big assumption, If the Front Band has already been secured to the gas system and and there is no longer any side to side play the gas system and front band is going to position itself dependent on the rotation of the barrel where it was installed. This may not be in compliance and the Front band Lip when it contacts the Stock Ferrule may or may not be at the best position. . If the Front Band has not been unitized to the Gas System it can be rotated to dead bottom by hand, the draw pressure produced with proper bedding will force the Lip to find the proper position on the Stock Ferrule. This dead bottom position can be marked and the unit taken off and unitized.

Everyone can choose the way they would like to fit the Gas System, some methods are faster and easier.. or it is the method in which a person was trained.. Match conditioning the M1A has progressed since the Service Teams went elsewhere for rifles. A case can be made for doing many M14's, such as the Service Teams needed, it is understandable to be expedient. However, when there is only one M1A at issue, and it happens to belong to you or me, I believe I will stick to Unitizing later... Art dance2
 

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I have used the method Art is talking about many times when unitizing gas cylinders. I would get the rifle set up with proper draw pressure, polish the stock ferrule and the front band lip etc. I then assemble the rifle without the flash suppressor or handguard because at this point they are not needed. Once everything is locked in place i fire up the Tig welder and tack weld the front band to the GS just enough to hold it in place. Once that is done i remove the GS from the barrel and install some copper heat sinks into the GS so i can finish welding the cylinder. FWIW i have welded over 100 cylinders and i have never heard of any of my welds cracking.
 

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Hey what heat setting do you run,and allso how do you clean and prep the cylinder and band before you tack and finish weldig.The reason I ask is I'm wanting to do this myself,Ive been welding for 23yrs.Stick,and Tig welding StainlessSteel,and CarbonSteel on presured piping systems,and I know that when we Tig we clean the pipe with an end grinder that has a "flaper"wheel,is it nessary to remove the parkerized finsh,or do you use some sort of cleaner.Thanks for any help you can give me about doing this,allso could you maybe post a couple of pixs of one youve done.
 
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