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G&P Buffer Tube Gas Tank for Marui 870


TheFull9

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just to be clear, you guys are considering sealing a real steel buffer tube but then what? The picture clearly shows that the buffer tube houses an inner tank assembly (which is longer) which threads into the buffer tube, the part which resembles a real ar15 extension just contains threads which I assume seals the inner tank to the grip assembly.

 

If this is so, the only way to use the real buffer tube as the storage device is to figure out how to attach this interface at the front onto a real buffer tube, which doesn't sound easy at all (bottom pic, seems this is one entire picture):

 

msp010t_1.jpg

 

 

In addition, all AR15 buffer tubes have drain holes either at the bottom or at the very least at the end to drain water...any ideas about how to seal one?

 

Now that I even think about it, only people who are considering using non traditional stocks like the ubr or m93 should care about this anyways, if you're using a normal AR15 aftermarket stock does it even matter?

 

WOCs have real buffer tube threading fwiw.

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Er - no it doesn't. Look at the photo closely:

 

The third photo (middle row on the right) shows the input valve for the expansion tank; you can see that that valve juts out beyond the rear of the stock adapter in the last photo (bottom, on the left). There's no way you would be able to fit a blanking plate or anything there with that valve sticking out, even if there were room in there for an expansion tank and a storage tank, which there isn't.

 

What is noteworthy is that fill valve in the top of the adapter (under that black plate secured with Allen machine-screws), which I presume can be used to fill the buffer tube tank. If that's correct, fitting a sealed RS buffer tube (assuming the threading is correct) is now even easier, because you don't need to fit an inlet valve or make provision for it to be refilled; all you do is screw it in place and fill it up through that inlet valve in the top of the adapter.

the way i see it, if they weren't optionally meant to be used without the buffer tube assembly, whats the point of making it into 3 pieces? why not make the buffer tube part of the stock adapter and have a larger buffer tube tank? they obviously wanted people to be able to install other buffer tubes and still have a gas source (even if severely limited).

also, if the buffer tube tanks have their own fill valves, why bother putting a fill valve on top of the adapter?

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because it allows you to keep the tube installed and fill it up without having to remove the tank. The fact is G&P makes buffer tubes for WOCs, retrofitting one for this kit would just require some simple machining and tapping of perhaps an inch of threading inside of a part that they already mass produce. 

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I reckon it won't be more than $170 and more than likely closer to $130. G&P are so good at what they do because they tend to concentrate on very few but extremely popular platforms, and make things in large volumes. Their AR parts are very reasonably priced in most cases for the quality, because so many people have AR's and G&P can keep cost down based on volume.

 

G&P are probably well aware there's a whole *suitcase*-tonne of people waiting for these, as evidenced by this thread, so they'll knock them out at a nicely affordable price and recoup their costs in a short space of time by selling loads of the things. 

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they obviously wanted people to be able to install other buffer tubes and still have a gas source (even if severely limited).

 

Edit - Do buffer tubes usually have threading inside the back end?  Not sure they do but I've seen more AEG ones than RS and I can't recall exactly.

 

Speaking generally I think everyone's got a tad carried away here.  In my humble interpretation, this product will work in the way displayed by the final picture supplied by G&P there, using all the included G&P parts and in no other way.  There's definitely not enough room in the adapter block for that to be used alone without the buffer tube and the supplied gas tank is most likely made the way it is (rather than a full on buffer tube full of gas) because it was cheaper and easier to manufacture the kit that way given the parts and machine processes G&P already have setup.  If you've got an AR stock with an open end (like the good old LE) you can fill up from there and presumably if you've got anything with a closed end you fill via the valve right up top there.  Although perhaps the interface valve between the cylindrical tank and the adapter block is one way?  Then again I'd think that was only necessary if there's an expansion chamber in the block and I can't tell if that's the case or not.

  

CKinnerley, is this modeled after the Mesa Tactical or the Cavalry Arms SS one?

 

You're asking me?  lulz.

 

Well, according to the research I literally did just now based on the info you've given to me there, it's the Cavalry Manufacturing SST they've used as a design base.  The Mesa Tactical adapter kit is a lot thinner and lower profile by comparison.  I'm guessing the Cav made it a lot easier given that larger internal space to route the connection system from the cylinder to the gas parts in the shotgun.

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just to be clear, you guys are considering sealing a real steel buffer tube but then what? [...] If this is so, the only way to use the real buffer tube as the storage device is to figure out how to attach this interface at the front onto a real buffer tube, which doesn't sound easy at all[.] In addition, all AR15 buffer tubes have drain holes either at the bottom or at the very least at the end to drain water...any ideas about how to seal one?

Yes, sealing a real steel buffer tube. You don't need to attach any interface to it; all that interface does is offer a QD valve to seal the individual canisters (the round silver tubes) to the adapter. The idea is evidently that you can switch out those canisters much like you can switch out the existing canisters in the existing stock. That QD valve just needs to be jammed open or removed altogether, as the RS buffer tube won't need to be QD, and the entire buffer tube pressurised. As for sealing drain holes, ten minutes' work with a TIG should resolve the problem, as would epoxy and a blanking plate.

 

the way i see it, if they weren't optionally meant to be used without the buffer tube assembly, whats the point of making it into 3 pieces? why not make the buffer tube part of the stock adapter and have a larger buffer tube tank? they obviously wanted people to be able to install other buffer tubes and still have a gas source (even if severely limited).

also, if the buffer tube tanks have their own fill valves, why bother putting a fill valve on top of the adapter?

Like the others say, they're made in three pieces to make them easier to make, and to let you switch out the QD canisters much like you switch out the existing gas tanks supplied with the gun. The fill valve is there to make the gun easier to fill with gas; to fill it at the moment, you need to either fully collapse the stock and unscrew the canister and screw in a replacement (you may need to remove the stock to get a grip on the knurled end of the canister) or fully collapse the stock and refill the canister while it's still attached to the gun from a gas bottle, requiring you to hold the gun barrel down and jam a gas bottle into the end of the stock tube. Again, like the others say, the fill valve means you can refill the canister while it's still in the gun, which means you don't have to faff around with the stock.

 

Sorry if I'm treading on your dreams, but there is simply no room in the adapter itself for a gas tank.

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no dream treading, just thats the way it makes sense to me. its made on a CNC machine anyway, so i don't see how it would be easier to make the adapter and buffer tube separately or not other than to have another purpose.

i also dont see how "faffing" around with a quick adjustable stock is any harder than positioning the gun in a way to fill it from the top. being that the former can be more easily done from a standing or kneeling position.

 

but i digress, ill wait and see.

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mmm indeed, all this discussion is nice but I guess it's probably best to wait for the thing to come out.

 

I definitely don't want to butcher my real M93 though since they're pretty rare, maybe someone is selling the STAR one somewhere still though.

 

tumblr_msyacft12L1svygtlo1_1280.jpg

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