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CKinnerley

G&P Buffer Tube Gas Tank for Marui 870

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I knew it'd happen eventually.  Not too surprising it was G&P either since they've been probably the biggest player so far in terms of other accessories for the TM 870.
 
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Kills a fair few birds with birds with one stone to my mind. They already make rifles designed for propane so this shouldn't struggle with the pressure like the Marui tanks do with makes their 870 a product I could actually buy (at last) as well as adding the AR accessory compatibility I know many have been after (myself included).  Looks like you can charge gas straight in from that valve in the top rather than having to take off the stock each time, which wouldn't be much of a drama with AR collapsibles but it does make life that bit easier.

 

Since the inner gas tank is removable as the outer buffer tube screws in the RS way I think it should mount AR lower base plates for some nice 1-pt sling options (on top of the QD sockets already integrated) and I'd wager RS/GBBr type pistol grips will fit as well which combined with the stock options makes for a lot ton of wiggle room to give it exactly the ergonomics the end user desires based on a whole range of products already on the market.  Adjustable LOP and grip angle (decided by the grip fitted) sounds about 1 million times better than the fixed stocks to me personally.

 

Only potential I see is that there looks like a lot of different points where components meet with o-rings to transport and store the gas, so hopefully they've got good tolerances and quality rubber parts on those areas to keep things non-hissy.

 

Also an old-school lighted forend for the RIS-adverse that still want to be a tiny bit tactical:

 

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It looks to me like the 'cartridge' that screws inside the buffer tube is basically a replacement gas tank, so you can unscrew one and screw in another rather than faff about trying to fill the stock tube with a gas bottle.

 

That's kind of neat, but at the same time, it does impinge drastically upon the already quite limited volume of the stock tube. The original M870's gas tanks are pretty small too (for no good reason in particular) but these look very small indeed.

 

[EDIT]Although, it looks to me like with the way the 'buffer tube' screws in, if you wanted you could just screw in a regular RS buffer tube (as long as it was gas-tight) with a fill valve in the end and fill the entire tube with gas. If you did that with a rifle-length buffer tube and fitted an A2 fixed stock you'd have a lot of gas to play with.[/EDIT]

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Any indication of price?

 

No hint at all right now, at least as far as I can see.  But the prototype there does look pretty sorted and ready to go in to production, might well be already.

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Those are plastic, I think. This is aluminium and has a ton of machining operations involved, plus it's the only example on the market. I'd say more like $150-200.

 

Are you serious? Plastic?

 

Anyway, this will finally come tru for me:

 

gallery-SSS-DSCF0005.jpg

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well, i would guess around 150 as well. the king arms stock adapter made for the Marushin M500 (same type of adapter as this, a copy of the Mesa Tactical adapter) was $75 and was made of aluminum.

 

 

i cant help but think of this + a 416c stock. but for another time.....

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oh, i just noticed another thing. it looks like its demoing 2 separate tanks. like one tank in the stock adapter itself and another add on expansion tank for more space for use with regular buffer tube stock options. it doesn't look like you need to use both.

 

unless you guys got that already and im just slow.

 

the only thing keeping me from abandoning all other ideas is that i know i suck with a shotgun after scrimmaging with ACM M500s for a while.

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^

What he said because another Serbu isn't such a bad idea.

 

The prospect of a gas cut down Ithaca / M870 MCS Breaching Config / Serbu Super Shorty is just too much to bear.

 

Especially as even at that size the capacity is still 10 tri-shots.

 

'FireKnife'

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oh, i just noticed another thing. it looks like its demoing 2 separate tanks. like one tank in the stock adapter itself and another add on expansion tank for more space for use with regular buffer tube stock options. it doesn't look like you need to use both.

 

While the adapter piece is fairly chunky, it doesn't look like there's a tank inside there, at least to my eyes.

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Looks like a peice of to tap for HPA aswell if your that way inclined. This is an AWESOME product just not a fan of pistol grips on shotguns!

 

Looks like that could possibly be modded to take CO2 carts aswell, maybe with some work.

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Are you serious? Plastic?

 

Anyway, this will finally come tru for me:

 

gallery-SSS-DSCF0005.jpg

 

I'd love to do this too but the M93/UBR uses its own buffer tube :(

 

but yes, pretty much what everyone said, this is probably one of the most forward thinking accessories ive seen in a while. However it is clear that the buffer tube is very unique and proprietary, there's just no way that you could use a regular AR15 one without heavy machining, seeing as how the rear end is hollow and threaded to accept the gas cartridges. Definitely will use WA/Real pistol grips though

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I'd love to do this too but the M93/UBR uses its own buffer tube :( [...] However it is clear that the buffer tube is very unique and proprietary, there's just no way that you could use a regular AR15 one without heavy machining, seeing as how the rear end is hollow and threaded to accept the gas cartridges. Definitely will use WA/Real pistol grips though

 

I think you could use real buffer tubes just fine, including the M93 and UBR ones, provided they can be made gas-tight. Instead of using the 'cartridges', you'd just seal the buffer tube itself up and put an inlet valve in it. Then you'd just fill the whole buffer tube (rather than the cartridge) with gas. Admittedly it would be slower to recharge but if you have to collapse the stock to unscrew the cartridge, screw in a replacement and then readjust the stock it wouldn't be much slower than the current design.

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oh, i just noticed another thing. it looks like its demoing 2 separate tanks. like one tank in the stock adapter itself and another add on expansion tank for more space for use with regular buffer tube stock options. it doesn't look like you need to use both.

 

unless you guys got that already and im just slow.

 

the only thing keeping me from abandoning all other ideas is that i know i suck with a shotgun after scrimmaging with ACM M500s for a while.

Yeah the 2nd to last photo does seem to suggest this! As if it can be used with and with out a stock! Good times.

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

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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.

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I don't get how you would get gas out of a horizontal gas tank.

The original doesn't differ much in its position and the gun shoots fine downwards.

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