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?
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!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.
Off again on this front band alignment issue. This post is excellent.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.