Could a classic mag regulator piston be safely rebuilt?

[lew]

-Wouldn't do the same job. The factory overpressure vent is to keep the chamber pressure from climbing too high. An add-on popoff of some kind would have to be tapped into the post-reg-seat system, such as screwed into the side of the valve body like a "Magic Box" pipe.

Now, if you disabled the body reg, as some people have, in order to run a foregrip reg, then you could screw the popoff into the VASA, or 'tee' it off the macroline-to-body fitting, etc.

Not sure you'd be able to find a nice, compact, 450-psi rated blowoff valve that isn't close to the size of a roll of quarters though.

Doc.

Pardon this neophyte, but what is involved in disabling the stock reg? I don't have any pressing need to do so, but I would like that information on-hand.

[caylegeorge]

I Imagine doc was referring to situations where people remove the back of the reg completely, and replace it with a machined cap, so that the air line pressure going into the valve feeds the dump chamber without any further regulation.

afaik this could also be achieved by removing the regulator pin and seat in the AIR valve so that no regulation takes place. But you would retain the weight of the back of the reg.

[forumreader]

I've rebuilt an AGD piston or two in the past and a few ANS pistons. The ANS disc seems to go to goo faster. Or maybe it was just the lubricant used. Who knows. Either way, a disc of goo does not seal.

In every instance, I did what I'm pretty sure Mr. Kaye did at the factory when AGD assembles them. I measured the total length of the piston, including the set screw. Then I opened the piston, punched a new disc out of 95 durometer .0625 urethane sheet, put the urethane, washer and spring back in there, put loctite on the set screw threads and then screwed it in until it looked right. I then measured with calipers and screwed the screw in or out until it matched my original distance. Done. I did not test it in a mule, but I'd bet it would vent at almost the same pressure it would before. As long as the rubber, washer, spring, and set screw are right, the only variable you have is spring tension. That is determined by how tightly that set screw is screwed in. Every time I've done it, it's worked great.

I just measured a handful of pistons here and a standard pressure piston (no circle on the face) has a free length of .760". I've got 3 high pressure pistons in front of me (circle on the face, meant for level 10 or other higher pressure dump chamber situations - maybe a hypermag? I'm not sure). One rings in at .742, another at .740, and another at .732. The high pressure pistons have a shorter overall length which means more pressure on that spring and more resistance before they start singing out the back of your mag.

Anyway, I'm fairly confident they set them by length at the factory and not to pressure, so we could safely do the same in a rebuild situation (length represents pressure). And, given the very correct discussion about the stability of not-co2 these days, you really don't need this to precisely vent. If it opens up at 600 or 850, it's going to tell you the same story.