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Sm1500 Assault Rifle

The "UNFAIR" Gun (Air Stock Write up now included)

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#1 imaseoulman

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Posted 22 March 2008 - 10:13 PM

<I just edited this to include a more detailed write-up; it begins at the end of the original post.>

So we had a NERF war today and I pulled out a project I recently finished. At our local wars we do not have a ban list...the general rule is that as long as one team doesn't have all the firepower, it's no big deal (I supply all the guns, so I try to balance it out). Well, today several people complained about the unfair advantage I had while using this:
Posted Image

I came up with the idea of an "Air Tank Shoulder Stock" completely independently and I got excited and told Sam all about it, and then he pointed me to This Link. I felt gypped (kinda like the time in third grade when I designed a reed switch magnetic train and then found out that the Japanese beat me to it) but my take on it was a little different than Carrtoon's. I wasn't trying for just one extra shot...but several.

The ball valve I used is a "low torque" ball valve (very easy to open and close) that I picked up from a local ranch supply store (gotta love Idaho). If I close the valve, the gun works just like a normal SM1500. If I open the valve, however, I can fill up the stock (somewhere in the ballpark of 125-150 cubic inches of volume) to 60 PSI to get many shots (around 30). I can just leave the ball valve open and fire off four quick shots or open and close the valve each time to conserve air.

Running at 60 PSI this thing gets AMAZING ranges (over 110') and is quite accurate. My friends wanted to ban it, not because of the pain factor (though anybody I NERF with knows that SM1500's don't tickle), but because of the combined range and ROF was so difficult to compete with.

The stock is quite comfortable (the length of the stock is perfect for my arms) and it gives the gun a nice "rifle" feel. It's easier to aim even if it is substantially heavier.

In the future I plan to add swappable turrets for faster reloading and a two-way pump for faster refilling.

What do you guys think? I'm especially interested in hearing from the guys who run 'Geddon and Apoc' just to make sure they wouldn't ban this gun. This is hands down my new favorite primary!


WRITE UP:
<note: I'm doing this write-up from memory as this blaster is on the east coast in storage until the summer, at which time I hope to take it out and hit up the east coast NERF wars>.
Alright, so first thing you want to do is open up your blaster and take out your air tank and take it with you to the hardware store. You're going to need to find a reducing tee (slip) that is just a bit too snug for the air tank to fit through (I think it's 3/4" PVC reducing tee, but I'm not positive). It should reduce to 1/2". While you're there, pick up the rest of the supplies you'll need, or order them from mcmaster.com.

1/2" street elbow, instant tube fitting, 1/2" PVC plug, some 1/8" ID 1/4" OD vinyl tubing (you'll need about two feet just to be safe), PVC Primer and Cement, 1/8" barbed tee (for connecting the vinyl tubing),

What we're going to do is use the reducing tee as a sleeve for the air tank and then connect a 1/2" PVC ball valve to the reducing tee via a street elbow. Here's what the PVC set-up will basically look like:
Posted Image
This will eventually be protruding from the left side of your blaster (unless you fire left-handed, in which case you can flip that).

Okay, so to actually attach this thing to your blaster you're going to need to cut down the reducing coupler so that it's just a little bit longer than the actual air tank (you'll need a little bit of a wall/lip that extends past the edges of the air tank to help the epoxy stay in place to make the seal). It should look like this:
Posted ImagePosted Image

Then you're going to sand out the inside of the reducing tee until the air tank can fit all the way inside (it should be a pretty snug fit), like so:
Posted Image
After it's in place, seal off all the seams (there are three "seams": one at each end of the tank and one where the reduce end of the tee protrudes from the tank). I used 60 second epoxy because it comes with those self-mixing nozzle things and is easy to get into small places. Also, before inserting the tank, I squirted epoxy inside the reducing coupler as well. When sealing all of this off, you want to make absolutely sure that there are no gaps anywhere between the tank and the coupler. Yes, just sealing the edges between the coupler and the tank where the reduced end protrudes should be enough, but it's better safe than sorry, and epoxying the base of the air tank will help reinforce that common trouble spot that is prone to shattering.

Now, to get all of this back into your shell, you're going to need to do some cutting/sanding/some sort of plastic removal. You'll need to drill a hole in the side of your blaster so the 1/2" reduced end of the coupler can stick out, like this:
Posted Image
and you'll also have to do some fairly intensive internal sanding to allow the shell to close properly.

After you've got that all put back together, you're ready to attach the valve. Before you proceed to this next step, ensure that your blaster is still working. If you're getting leaks out the barrel of your blaster, it's because your firing pin is slightly pulled back; you're going to have to do some more repositioning/sanding to eliminate that. Okay, so if everything is working, and the tank holds pressure and fires just fine, drill a hole into the side of your air tank (which should be visible, now, from the outside via the opening in the 1/2" reduced end of the coupler). This is a close-up of where you're going to drill:
Posted Image
The size of the hole you're going to drill depends on what you're hoping for.
If you just want to increase rate of fire and have more shots before re-pumping, make it a small hole, 1/8" in diameter, or even 1/16".
If you want to turn this into a tank expansion (which will probably get it banned at most wars, but will dramatically improve range, while increasing the amount of air used per shot, resulting in less shots before needing to re-pump) then drill the hole as wide as possible, no less than 1/4".
Use a Q-tip to clean out as much of the plastic debris as possible that fell inside the air tank.

Now attach your street elbow to the coupler and your ball valve to your street elbow, using a short length of 1/2" PVC to make the connection. Primer and Cement these parts together.

Close your ball valve and make sure the gun operates properly. You will notice, now, that it takes more pumps to pressurize than it did before. This is because of the space inside the PVC elbow. This is why drilling the hole more widely turns it into a tank expansion. Leaving the hole as narrow as possible will also help eliminate wasted air during rapid fire, as will be explained later.

If everything is working properly, it's now time to make your "air shoulder stock." For mine, I used 2" PVC (I think, I'm pretty sure it's not 3"). You can tell from the picture what sort of elbows, tees, and end caps I used. The whole PVC stock is one large air tank. Mine is, in fact, very large and you could make it much smaller and still achieve great results.

To determine the length of stock I wanted, I just held the gun up like I would a rifle and held a piece of PVC up to it, pushed it against my shoulder, and then marked where the end should be. Not really an exact science, but I just wanted it to feel natural in my hands.

So make your stock whatever shape you desire (I added the cross section just to increase the volume) and seal everything off with PVC cement and primer. It should be a closed system, AIR TIGHT.

Now you're going to attach it to your blaster. I just used copious amounts of hot glue and zip ties (though after the glue dried, I removed the zip ties). With this much contact surface, hot glue is plenty strong enough, and allows for it to be somewhat easily removed later.

After the stock is attached to the blaster, drill a hole in the stock at a point near the ball valve in such a way that vinyl tubing running from that point to the ball valve won't be in the way of anything. The hole should be just big enough that you can shove your vinyl tubing into the hole. Vinyl tubing, being soft, will create its own seal fairly well if the drilled hole is good enough, but goop it for good measure.

Cut the tubing at length that is just long enough to reach the ball valve without any kinks. Next, you're going to drill a hole in a 1/2" PVC plug and insert the tubing just as you did in the air stock, and gooping again for good measure.

Finally, plug the endcap into the open end of the ball valve and you're done, unless you want the option of being able to fill your air stock with an external pump/inflator. If you want to be able to connect it to an inflator/bike pump/whatever, just cut your tubing that runs from the stock to the ball valve and insert a barbed tee. Connect a short bit of tubing and then a small check valve and finally an instant tube fitting.

Operating the blaster:
Open the valve and fill up the stock (could take a while, depending on the size of your air stock). Close the valve and fire. Open and close the valve to refill your blaster's firing tank. If you need to get a lot of shots off really quickly, just leave the valve open. This is the situation in which it's most ideal to have drilled the smallest hole possible in the blaster's air tank. If the hole is small enough, it will act as a flow restrictor, preventing excess air from escaping via the barrel after the dart has been fired and before the trigger is released.

Any questions? Comments? Flames? Praise?

Edited by imaseoulman, 23 December 2008 - 03:29 PM.

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#2 Cannonball

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Posted 23 March 2008 - 01:33 AM

I like it. Personally, I've been trying to figure out a way to do something like that with the spare at3k I've got laying around. I may experiment with what you've done a bit. I've got a question though. Are you filling the tank up with the pump on the blaster or a compressor? and if its the pump, how many pumps to fill it to get 30 shots out of it?
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#3 xNFx 37

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Posted 23 March 2008 - 06:56 AM

You've posted like 5 mods in the past month or two. But, they've all been new, amazing, and very useful.

My friend has an SM1500 (his little brother) and I told him I'd trade him a stock longshot and a modded 2k, but he STILL said no! <_<

Anyways, Really nice mod, 30 shots has to be hard to compete with at 110 feet each shot. This shoulder tank Idea was also brought up in one of Zero's homemades
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QUOTE
it also has a cock on it


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#4 mystefansdontflystraight

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Posted 23 March 2008 - 07:40 AM

Sick. Thats all I can say. 30 shots with the extra valve hooked up is amazing. Im not surprised that your local nerfers want it banned. I wish I had an sm1.5k now <_<
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QUOTE(Blacksunshine @ Dec 24 2009, 02:15 PM) View Post

QUOTE(white moonlight @ Dec 23 2009, 01:29 PM) View Post

It's just screaming to be rearloading...

I seen a movie about that once.



#5 imaseoulman

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Posted 23 March 2008 - 09:46 AM

Cannonball-
Usually I fill it up via an electric inflator (12V, usually used for inflating a car tire in the middle of nowhere). I've only filled it up twice using the regular pump, and that takes around 180 pumps...so not very fun. I also, sometimes, fill it up via a two-way tower bike pump (extremely high output). Once it's filled up though, I just continue to pump it up with the regular hand pump. Between rounds, if the pressure has dropped enough from doing more shooting than pumping, I'll just top it off with the inflator (takes about 60 seconds).
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#6 nerfer34

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Posted 23 March 2008 - 10:01 AM

That looks like so much fun to use.

Great job, Are you going to paint it? Then it would look even cooler.
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<!--quoteo--><div class='quotetop'>QUOTE</div><div class='quotemain'><!--quotec-->God Damn it Groove, you stole my kill.<!--QuoteEnd--></div><!--QuoteEEnd-->-OMC

#7 imaseoulman

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Posted 23 March 2008 - 10:32 AM

That looks like so much fun to use.

Great job, Are you going to paint it? Then it would look even cooler.

Man...you sound like my wife! Seriously, right after I finished it, I brought it out to the living room to show her and asked her what she thought. She thought it was a bit too much work for one gun (though it's actually easier than a lot of other mods I've done) and that it needed to be painted. After I gave her that, "Are you serious?" look, she replied, "What? I like pretty things." (Her favorite guns are the Blast Bazooka and Big Blast because of their basic shape and paint jobs..."they're pretty").

As to whether or not I'll paint it...I don't know. If I can figure out how to do the "relaxing painting by hand" that FA_24 keeps talking about...maybe. Also, I want to make sure it's legal at most wars before I put more work into it. If I did paint it, it would probably just be something simple, like matching the stock to the existing color scheme of the actual gun.

Edited by imaseoulman, 23 March 2008 - 12:03 PM.

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#8 bogboogalars

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Posted 23 March 2008 - 10:54 AM

At the end of your first paragraph "they're pretty" it reminded me of jeff dunham..."It's pretty"
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#9 OfAllTheNerf

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Posted 23 March 2008 - 11:10 AM

Nice. How th hell do you get all the time for these things?

I've been wanting to make a semi-auto at2k/sm1.5k, but was thinking of only getting, at max, 4 shots... How long are those barrels?

In the words of VACC, "that's a pretty intense piece of equipment you've got there."

Edit: Are those barrels CPVC?

Edited by OfAllTheNerf, 23 March 2008 - 11:10 AM.

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#10 chalywong

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Posted 23 March 2008 - 11:12 AM

I think what you made is a great piece of work but I'm gonna have to side with the idea of banning it at normal wars. I believe that when you start having to you use things like air compressors and air tanks it just makes the game unfair. Every springer should need to be cocked and every air gun should be pumped, taking away the pumping of a air gun and on top of that having a turret is just way too imbalanced.
[indent=1]If everyone had similar guns like captain slugs BOB, or Volley Titan, I would say this is perfectly fine but going up against regular blasters and even powerhouse blasters like crossbows and big blasts its still unfair. You can outrange, and have more ROF than anyone and on top of that you don't have to pump? Like I said its an amazing idea but its just not practical/fun for a war when people have "regular" modded blasters.
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#11 imaseoulman

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Posted 23 March 2008 - 12:00 PM

Thanks for the input. I do have to pump though. If the round lasts a little while I have to repump the tank. Typically I'm just constantly pumping when I'm not actively engaged in combat. While in combat, I can get four shots off without having to reload, but that's no different than a Big Salvo (with comparable range), and less than a Blastfire or Hornet. My PC's and MS's hit close to 100' and can fire off thirty rounds (at least the MS's can) before needing to repumped. I guess I'm just asking where the line is. Again, thanks for your input; I'm not trying to argue, just a little debate so we can hash this out and come to a concensus.

So I totally missed this:

Nice. How th hell do you get all the time for these things?

I've been wanting to make a semi-auto at2k/sm1.5k, but was thinking of only getting, at max, 4 shots... How long are those barrels?

In the words of VACC, "that's a pretty intense piece of equipment you've got there."

Edit: Are those barrels CPVC?

To answer your questions:
1) Time? These don't take all that much time. This SM1500 took a total of maybe three hours. The "Big Big Blast" took less than two hours. I don't know how many guns I've modded in my life (probably around 80-100, only a few of which are springers), but I can assure I've gotten much faster than when I first started. I'd say that on average I spend about three hours a week on modding (some weeks more, some weeks none), except when I'm trying to finish multiple projects by a deadline (like an upcoming war).
2) The barrels are ten inches. Twelve inch barrels might get a little more range, but I don't need it and that would make it even longer, which I don't want either.
3) Yes the barrels are CPVC. I find that CTD's work EXCELLENTY in CPVC and CaptainSlug-styled-darts work best in PETG (I'm not saying that will be the case for everyone, just in my experience). For long range "air powered" guns, I prefer CPVC with CTD's.

Edited by imaseoulman, 23 March 2008 - 12:13 PM.

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#12 oodalumps

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Posted 23 March 2008 - 12:19 PM

You should make the valve between the tanks close when the trigger is compressed. Would be very easy to do by replacing the ball valve with a blowgun (not the kind that shoots darts), then putting it in front of the trigger using rubber tubing. Then with some string or whatever, attach it to the trigger mechanism.
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#13 imaseoulman

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Posted 23 March 2008 - 12:34 PM

I'm really not 100% clear on how these "blowguns" work. I keep reading about them in homemade threads (usually in conjunction with sprinkler solenoid valves) but I'm not quite sure how they actually work. Also, I'm not sure how much they cost (my low-torque ball valves were $1.97) or where to find them (McMaster part #?). If somebody wants to point me toward a good explanation of how these work or explain it to me here, that would be great.
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#14 oodalumps

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Posted 23 March 2008 - 12:44 PM

I'm really not 100% clear on how these "blowguns" work. I keep reading about them in homemade threads (usually in conjunction with sprinkler solenoid valves) but I'm not quite sure how they actually work. Also, I'm not sure how much they cost (my low-torque ball valves were $1.97) or where to find them (McMaster part #?). If somebody wants to point me toward a good explanation of how these work or explain it to me here, that would be great.



Posted Image

When you press the trigger down on the blowgun (red part), the air is free to flow. When you let go of the trigger, the trigger decompresses and the path is closed again. You can attach brass fittings to either end of a blowgun. I think they cost 5-10 dollars.

Not sure if that's exactly what you're looking for, but thats some basics about them. you'd have to wrap rubber bands around the trigger it to keep the valve open for my idea though.

Edited by oodalumps, 23 March 2008 - 12:47 PM.

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#15 Cannonball

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Posted 23 March 2008 - 03:25 PM

I'm not sure if your gun should be banned or not. It isn't exactly a titan but there is that some what rapid firing going on. (as in, you can continue to pull the trigger, not like say a rapidfire 20 where you can hold the trigger down) I could see where that would seem unfair with that kind of distance going for it as well.

I do have to say that I'm not too fond of having to fill the tank with something other than the pump built in. I think a more practical one should have a smaller tank and be able to be filled by the built in pump. Sure the number of shots decrease, but I think it would be less likely to be banned. If anything though, I don't think it should be banned just because it's unfair and people didn't think of doing that to their own guns.
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#16 imaseoulman

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Posted 23 March 2008 - 03:57 PM

The tank doesn't have to be pumped via an external pump...it's just a lot easier that way. I can pump it up at the beginning of the war (i.e. in the morning before starting) and then just keep pumping throughout the day. It doesn't take too much effor to keep it filled, getting filled is the burden (a few minutes of straight pumping). I do agree with you that "unfairness" shouldn't be grounds for banning a gun.
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#17 d0nk3y k0n9

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Posted 23 March 2008 - 04:02 PM

If you're worried about its legality, just compare it to existing mods. For example, captain slug's external tanks.
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#18 Cannonball

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Posted 23 March 2008 - 11:56 PM

The tank doesn't have to be pumped via an external pump...it's just a lot easier that way. I can pump it up at the beginning of the war (i.e. in the morning before starting) and then just keep pumping throughout the day. It doesn't take too much effor to keep it filled, getting filled is the burden (a few minutes of straight pumping). I do agree with you that "unfairness" shouldn't be grounds for banning a gun.



Oh i know you don't have to refill it with an external tank. I was just saying that I thought it'd be better to make one that required only the use of the built in pump with a not so large amount of pumping. That was my fault though, I didn't explain myself to clearly. I'm going to run out tomorrow actually to the hardware store and check out the piping and stuff to see what I can do with my at3k. thanks for the inspiration.
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#19 General Cole

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Posted 24 March 2008 - 05:12 AM

Last I checked the concensus was that if it used something other than a Nerf or premade knock-off tank or plunger, it was not legal. BUT, I wouldn't leave it at home. I would also look into the Kobalt belt tanks for powering this guy instead.
We should stop calling out/making fun of/pissing GC off. He's actually contributed and is available for trade. He's a better than average member no doubt. Got your back Cole.
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#20 sam

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Posted 24 March 2008 - 11:59 AM

Man, I was hoping it was a noob that posted this topic so I could do this:
Thats not a SM1500 assault rifle, THIS is a SM1500 assault rifle:
Posted Image

But anyway sweet mod, way better than what you originally wanted to do. I'd like to hear more about those easy open ball valves.
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#21 nerfboi

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Posted 24 March 2008 - 12:10 PM

I think the ball valeves are used to fill the REAL SM1500 tank. Am I right?
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#22 imaseoulman

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Posted 24 March 2008 - 01:10 PM

Man, I was hoping it was a noob that posted this topic so I could do this:
Thats not a SM1500 assault rifle, THIS is a SM1500 assault rifle:
[IMAGE OF SAM'S SWEET SM1500]
But anyway sweet mod, way better than what you originally wanted to do. I'd like to hear more about those easy open ball valves.

Dude! I love the pump handle! What did you use for the grip? I'm probably going to do something similar. I REALLY like it. But yeah, I don't even remember what I orginally wanted to do...I just remember that it was something ridiculously crazy and impractical. More about the valves in the response below.

I think the ball valves are used to fill the REAL SM1500 tank. Am I right?

Yes the ball valve (singular) is used to fill the air tank. I got them from a store called C-A-L Ranch. I don't know how widespread that store is, but they're all over the place in Southeastern Idaho. I was a little worried about them getting a perfect seal because they're so easy to open and close but I haven't had any problems with them (even if there was a slow leak from one side of the valve to the other there really wouldn't be any significant change in performance for this application). The ends a bit bigger around (thicker walled) than normal 1/2" PVC ball valves but from the base to the tip of the handle, they're about the same. The handle itself is much bigger than standard ball valves, and that probably aids a little in opening and closing it. I'll see if I can find them on line somewhere.
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#23 sam

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Posted 24 March 2008 - 01:35 PM

The pump handle is 3/4" PVC tee with some 3/4" PVC and an endcap. It's attached with e-tape and hot glue, but I plan on putting a screw in it later on.

Originally you wanted a singled SM1500 with a clip, and smaller air-stock. I pictured it on a old version SM1500.
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#24 imaseoulman

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Posted 23 December 2008 - 03:25 PM

Due to the recent resurgence in interest in the air stock concept, I decided to edit the first post to include a write-up. I'm just posting that here so that if anybody comments on it or asks any questions, that won't get flamed by any wannabe moderators for necroing.
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#25 TantumBull

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Posted 23 December 2008 - 04:37 PM

Thanks a ton for the right up. I still have a couple of questions, though.

1) The tank reinforcements you mentioned is basically the tank being inside that reducing T, am I correct? Wouldn't that still mean that the piece that seals the valve is still vulnerable to all the pressure in the stock? I thought that was a piece that broke under high pressure?

2) With this set up, the first shot is going to be the most powerful, and the first time you open that ball valve, all the pressure in the stock will equalize in the valve as well. The valve, even with the T reinforcement, can take this kind of pressure without detonating? (Keep in mind this is all assuming that the PSI in the shoulder stock is going to be higher then the PSI in a normal 1.5K valve at 4 pumps.)

3) What size hole did you drill into the air tank? 1/8"?
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