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#1 Whisper101

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Posted 04 March 2011 - 11:50 PM

-FOMAS-

Cool Philosophical Babble: There is a blatant lack of new, homemade air guns on this site. I could hypothesize and speculate, and generally get nothing done for days about why exactly this is, but it may just boil down to the fact that air guns are harder to make and therefore take more time to build and make work consistently. They’re in a different class from homemade springers because lines between nerf and paintball begin to blur when considering the homemade nerf air gun. Often times the air source for these guns are HPA tanks used in paintball. These and all of the fittings associated with them are expensive, and deter many people, myself included. Rather than turn away from homemade nerf airguns altogether, I set out thinking about how to make a relatively inexpensive and relatively well-performing homemade nerf air gun. I think I succeeded on both counts. As for you nitpickers, I mean the guns that have air TANKS, either pin or backpressure, so I better not get any smartasses saying, “well technically, all nerf guns are AIR guns…”. That pisses me off to no end, just like whoever said that we shouldn’t call our guns guns. Idiocy!!

Next up, a big shoutout to Lt. For inventing the PVAT, and for also jumpstarting my brain by hinting at something along the lines of this project. I thought, after having made my own PVAT and seeing it’s power and potential, that the tank itself finally had to be harnessed in the form of a gun. This is where the inspiration for this gun came from if any of you are wondering. Lt. also took the time to answer my many questions and was more than patient in helping me work out the kinks in my original PVAT.
So the general premise of the L+LPVAT is a PVAT filled L+L. I constructed the “shell” from one of the various write-ups around the haven. You will need everything except anything to do with firing of a springer L+L. For this reason, I won’t put in the write-up how to make the shell, as it is readily available elsewhere.

Places to look for additional information:
- Lt. Stefan’s PVAT writeup: http://nerfhaven.com...c=19073&hl=PVAT
- Hereticorp’s L+L writeup- no pics, but if you are literate this will help: http://nerfhaven.com...c=19073&hl=PVAT
- CaptainSlug’s partlist and template files: http://nerfhaven.com...showtopic=13999
- Slug’s guide to machining plastics as well as the tutorial on solvent welding could be useful, but only if you haven’t read them before. If you haven’t read those two guides or something more comprehensive, you shouldn’t be building this homemade.

On the topic of who this is geared towards, I would not recommend starting with this as your first homemade, or even your second, third or fourth. It’s fairly involved in cutting the “shell” parts, and getting the PVAT to seal perfectly can sometimes be a bitch. Bottom line: If you have made a polycarbonate homemade and a PVAT before, this gun is one you should be able to build.

Begin Picture Barrage:
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Finished product- there are no in progress pics, as I never take them. Ever.
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Trigger mech
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Side off
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Side off closeup
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With stock
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Stock and hopper
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Stock and dipshit barrel, used for general jackassery when engaging in shenanigans
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Shotgun! Oh mah gawd!!
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-wait for 2nd post-

Edited by Whisper101, 04 March 2011 - 11:52 PM.

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#2 Whisper101

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Posted 04 March 2011 - 11:52 PM

It’s one of the fittings show on the top left of the page (http://flexpvc.com/c...VC-Distributors), and a 1.5” X .5” reducer bushing, with a segment of ½’ PVC in the end.
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Barrels are 2” long and heavily beveled and sanded for easy dart feeding. They are held on by endcaps that have been drilled out.
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The whole setup
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A little graphic I drew for the system as a whole: FOMAS: Foam One Man Assault System
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Hole placement reference pic
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Trigger measurement reference pic

The FOMAS name, as states above, stands for Foam One Man Assault System, and as you can see, there is a veritable plethora of different setups for the gun. I compare it to what Hasbro was trying to do with the Recon, but unlike the Recon, the FOMAS can achieve much better range by being shot than by being thrown. This has been scientifically tested in a controlled setting. This means in a fit of rage whilst modding a recon in my basement. The name also sounds cool.

So the shell modifications have really been covered. The other part of the gun, the tank, has had a few modifications done to it as well. Instead of a plastic barb, I used a brass one and drilled a 3/8” hole in the exposed 1” PVC portion of the tank. I used some pliers to self-thread the threaded end of the barb into the tank, and then super glued and gooped over that. Also, I glued an o ring to the back of the bushing at the front of the tank. The rubber to rubber seal seems to work better for me. The spring Lt. mentions in his writeup is an ACE #62, but at least at my ace #62 did not fit correctly. You’re on your own in this regard. Don’t forget the washer on the back of the carriage bolt; it helps with the trigger stroke. A very important thing to note is the holes that were drilled directly into the tank. THEY DO NOT GO THROUGH TO THE INSIDE OF THE TANK. This will obviously cause leaks, which are bad. To get a constant depth in all my holes, I simply wrapped some tape around my 7/64” drill bit ¼” or so from the tip. That way all the holes would be ¼” deep and from there I could thread them and insert screws.

This gun really isn’t too hard to build. Just machine and assemble everything from the L+L that is not involved in dart propulsion, and then look at the pretty pictures. If you really just want the bare bones, the back piece that the endcap is glued/puttied to is not completely necessary. It does help with keeping the side plates together and makes the gun a bit sturdier in my opinion. It also gives the builder an excuse to carve out a cool iron sight; something I’ll never pass up. The sideplates are also a little bit different from those of the L+L, but I only did this to accommodate the pump, as well as for aesthetics. Other places/modes of pumping may result in different sideplate dimensions.


Ranges…Because I KNOW you goobers will ask.
OK, so where I currently hold my place of residence, approximately 2.5 feet of snow is molesting the ground.

The ranges below are relative:
-Single 18” CPVC barrel: dart penetrates the front of a stampede box, and then exits cleanly out the backside with some force. That or the hot glue head falls off.
-Hopper w/12” CPVC barrel: Darts penetrate front of box, and either dent or stick in the back of the box. Same deal with the heads.
-Shotgun attachment: A few darts penetrate the front of the box, most stick in the front, and the rest dent or bounce off the box. Again, same goes for the heads.
-I also have a missile attachment that I am still fiddling with. Ranges could be 6 feet or 60 feet.

The titan pump that serves as the air source is plugged, but I did this only because I wanted to see how many pumps was physically possible. 6 is the absolute max.

Questions? Comments? Hooligans who enjoy engaging in flame slinging shenanigans? PM’s are OK too.

Edited by Whisper101, 04 March 2011 - 11:54 PM.

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#3 TantumBull

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Posted 05 March 2011 - 03:36 AM

You've got yourself a real solid blaster there. Looks very nice and seems like it would be a great, much more compact alternative to a 4B or it's variants. The inlined shotgun attachment is also pretty damn intuitive.

The only thing that I might be worried about is the end cap for the stock. It appears to only be e-putty'd on there. Some mechanical attachment would probably be ideal, maybe through an L-bracket of sorts? But I guess if the hole is a perfect size the friction fit should help keep it in place. Still something to maybe consider.
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#4 Kid Flash

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Posted 05 March 2011 - 03:44 AM

This looks pretty interesting, and I also made something:

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EDIT: Tried to make there be less dead space, and to fix some off imperfections in the black border.

Edited by Kid Flash, 05 March 2011 - 04:16 AM.

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#5 blitz

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Posted 05 March 2011 - 07:06 AM

The reason there has been a lack of homemade airguns is because they are banned at nearly all wars.

The blaster is cool, however. Props to you.
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#6 Whisper101

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Posted 05 March 2011 - 09:47 AM

@tantum: It appears I'm not the only one to have though of the inline shotgun attachment. FOME tried the same thing a while back, but he couldnt get consistent results. The inline shotgun peice actually took me more time than the actual gun to build and perfect, as the dart feeding was so finicky. It works perfectly alomst every time now.

@kidflash: I love it. It's actually sick. May I ask how you made it? I'm very interested in pursuing this further...

@blitz: Hmm, that's a good point, but if I unplugged the pump it would still get almost as good ranges, and upon demenostration to war officials, I can't see them banning this and allowing, say an unplugged, hoppered, 4B. I hope to et the package shipped out this weekend BTW.
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#7 taerKitty

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Posted 05 March 2011 - 10:41 AM

Great job. I've long viewed the PVAT as an interesting experiment, one for perhaps a 'rainy day', but the lack of blasters utilizing it caused me to plut it lower on the priority list. I may give this a try.

Luckily, our local war doesn't ban homemade airguns simply because they're homemade. If they're unsafe (overpowered or poorly constructed), I'm sure the war organizers would punt them, but then again, I'd not want to be on the field with them anyhow.

Great job!
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#8 Kid Flash

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Posted 05 March 2011 - 10:56 AM

@kidflash: I love it. It's actually sick. May I ask how you made it? I'm very interested in pursuing this further...


For the "logos" if you want to call them that, I use photoshop and illustrator. I'd be interested in getting one of these homemade airtanks... I just don't think I could make one. Always worth a try.
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#9 venom213

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Posted 05 March 2011 - 02:09 PM

Very nice work. I've been a major advocate of (reasonable) homemade air blasters for years now. This is a nice step towards making them more accepted. I've taken note of this and the original PVAT for some future projects....
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#10 Whisper101

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Posted 05 March 2011 - 04:34 PM

Yeah, they're harder to make, and very finicky, but they're so versatile and really should be allowed at wars. If constructed by someone who is sane, safe, and knows the limits, they're no more dangerous than a 4B.
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#11 Ice Nine

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Posted 05 March 2011 - 05:35 PM

I can't see them banning this and allowing, say an unplugged, hoppered, 4B.


Yeah, they're harder to make, and very finicky, but they're so versatile and really should be allowed at wars. If constructed by someone who is sane, safe, and knows the limits, they're no more dangerous than a 4B.


It's worth noting that the "best" 4Bs nowadays are forward-pump-replaced WITH stock OPRV solvent welded into the tank. Also worth noting is the fact that 4Bs by construction (and LBBs) are two mostly disjoint tanks with low airflow paths between them. While I'm not comfortable commenting on volumes between this and the more prevalent large-tanked manufactured blasters, their construction puts a lot more limits on the potential for the gun. Even airflow bridges that I've heard Drac and SVT trying out between back and front tank probably don't do very much.

This tank is much more similar to a Titan, which is a large, extremely efficient tank that will outshoot a comparable 4B and LBB without a question. It's probably worth considering, then, that Venom, just a few threads down, posted an extremely robust homemade OPRV, and that McMaster sells numerous good options for an OPRV (from fixed at values from 25 to large psi, to adjustable from 25 to 50 psi).

Keeping the stock OPRV actually active on the Titan pump (or, as would be my personal preference, inbuild an OPRV into the tank) will go a long way towards convincing people that these will continue to be safe and acceptable guns.

Edited by Ice Nine, 05 March 2011 - 05:36 PM.

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#12 taerKitty

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Posted 05 March 2011 - 08:57 PM

Keeping the stock OPRV actually active on the Titan pump (or, as would be my personal preference, inbuild an OPRV into the tank) will go a long way towards convincing people that these will continue to be safe and acceptable guns.

So will performance testing it side-by-side against a war-legal blaster. Grap 10 identical darts each, pump each until the OPRV kicks in, test for range (level shot, same height, etc.) Then let the war organizer decide.
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#13 Ice Nine

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Posted 05 March 2011 - 10:38 PM

Keeping the stock OPRV actually active on the Titan pump (or, as would be my personal preference, inbuild an OPRV into the tank) will go a long way towards convincing people that these will continue to be safe and acceptable guns.

So will performance testing it side-by-side against a war-legal blaster. Grap 10 identical darts each, pump each until the OPRV kicks in, test for range (level shot, same height, etc.) Then let the war organizer decide.


Why waste half an hour of war time?

In a more serious rebuttal, with slug darts (which seem to be the norm rather than the exception in warring, for the most part), past about a muzzle velocity of about two hundred feet per second, the range increase in slug darts is marginal at best. When Klaviel brought a chronograph to whatever Chicago war was the first week of October last fall, Ryan's Rainbowpump managed 212 fps, his AT3K 275 fps, and my 4B (after frantic pumping to equalize the OPRV a bit) 320 fps. The difference in ranges between these three guns with slug darts is not very large.

If you were only testing absolute range in that scenario, it would be extremely easy to get a plugged airtank like that past 300 fps, probably pretty easy to make it go much faster, and the range compared any number of powerful unbanned guns would not be significantly different. This does not indicate how much more it would suck to get shot from ten feet away with one of these when the dart is still carrying a significant portion of its kinetic energy at the muzzle.
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#14 Whisper101

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Posted 05 March 2011 - 10:59 PM

Or you both could stop arguing and make sure you understand that it is not at all necessary to plug the pump. That seems to be the debate here. let's break it down: Plugged titans are not allowed anywhere. My tank is smaller than the titans, and therefore has less volume. Unplugging it would give me an unplugged gun with a smaller tank. On paper, it war legal, and 1 shot will show any war official that it is. Seriously guys, this is simple; it's easy to push a gun to it's fullest potential and then dumb it down for wars.
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#15 NerfGeek416

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Posted 05 March 2011 - 11:01 PM

If you need to limit power, just put a tee between the gun and the hopper. You can now adjust the dead space to weaken the gun as necessary.
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#16 utahnerf

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Posted 06 March 2011 - 01:10 AM

I believe that Pvats should be allowed at wars. They are essentially a homemade BBBB/3k/4k/2k/(pin tank), tank. I do agree that it is ultimately up to the war host to decide if they will allow it. Pvats beat shitcannons.
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#17 PVC Arsenal 17

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Posted 06 March 2011 - 02:30 AM

On the topic of who this is geared towards, I would not recommend starting with this as your first homemade, or even your second, third or fourth. It’s fairly involved in cutting the “shell” parts, and getting the PVAT to seal perfectly can sometimes be a bitch.


Perhaps you can avoid both issues by taking a slightly different approach as this SpudFiles member did. At the very least, you can eliminate the polycarb shell in favor of a simple [Fimo] grip mounted directly to the chamber with a pushrod trigger linked to the piston. Better yet, (and I don't mean to knock the PVAT) you can skip the sealing issues with a simple fixed diaphragm coaxial gun.

In any case, good work. The journey towards the truly perfect Nerf gun gets shorter with every new creation posted. Maybe we can get there faster if we don't discourage new builders from taking on challenges. <_<

Edited by PVC Arsenal 17, 06 March 2011 - 02:31 AM.

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#18 Whisper101

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Posted 06 March 2011 - 10:51 AM

@PVC: But eliminating the shell would take the fun out of it! it's true; it's not strictly necessary, but then it wouldn't be a L+LPVAT, or FOMAS. PLus, the shell is purty. I think I take your hint about discouraing new builders, but I speak from experience when I say that it's good to take challenges, just not unreasonable ones. If a new nerfer tries to make this as thier first homemamde, chances are slim, not impossible, but slim that it will come out how they want it to. They might get frustrated and drop nerfing altogether which would be a shame. I was just saying that this is probabaly a good homemade to work up to.
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#19 VACC

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Posted 07 March 2011 - 10:03 AM

I guess I should chime in here, though my chimes tend to take the unintentional tone of a gong, since I've often been associated with any and all gun restrictions; and in this particular case the notion is actually fairly accurate. I've blanket banned homemade air guns at MY wars (I've no magical powers over other war coordinators) since 2002 (my last trip to Armageddon). This ban had nothing to do with oprv's, or their comparison with existing nerf guns. This was because motherfuckers were bringing ball valve or solenoid operated monstrosities with enourmous tanks, whose only function were to fling a single dart hundreds of feet. It in no way resembled nerf as we knew it, and it simply was not fun. The reason that I and many of us continue to blanket ban them, is not because no homemade air gun is reasonable, but because the majority are not. You have to understand that ANY blanket ban is not constructed to regulate a small war where you know and trust everyone. They're neccessities, instead, for massive wars like Apoc, where the coordinator knows a fraction of the participants and has no time to check everyone's weaponry.

This comes back to your assertion that someone who's knowledgeable and trust worthy should be allowed to use a homemade air gun. Should I line everyone up at Apoc and count off: "Douchebag, Douchebag, Douchebag, Good Dude, Douchebag, Good Dude..."? It's just not feasable.

Anyway, I don't mean to lend an air of negativity to this thread, but the topic was broached and I won't want to discuss it in a war thread. It's a badass nerf gun, and it looks like a lot of fun. I love that people like you and slug continue to make these monstrosities. Even if you can't use them at some big clusterfuck of a nerf war, you can certainly find somewhere to shoot your friends with them. Besides, one of these days someone will make something so simple and replicable that everyone will move towards it. Before the plusbow a lot of wars banned homemade guns altogether, and now I rarely see an actual nerf gun anymore. Point is, don't worry so much about what other people will allow. Throw your own wars and kick your friends' asses until they all want one.
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#20 Whisper101

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Posted 07 March 2011 - 03:43 PM

Yeah, you're right; checking everyone's homemade air gun at a large war is not a good idea. That's a good point though, and other solutions could certainly be worked out with some thought. The FOMAS is not intended to be one fo those ball valve or solenoid guns you mentioned at all, that's why it's the assault SYSTEM. I completely agree with what you're saying VACC, and maybe in the future if these become more popular, it'll be sort of assumed that they're ok for wars. We'll see what sort of modifications people make to the basic design...
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#21 Draconis

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Posted 07 March 2011 - 06:11 PM

Should I line everyone up at Apoc and count off: "Douchebag, Douchebag, Douchebag, Good Dude, Douchebag, Good Dude..."? It's just not feasable.


Sounds like the best game of Duck, Duck, Goose! ever!
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[15:51] <+Noodle> titties
[15:51] <+Rhadamanthys> titties
[15:51] <+jakejagan> titties
[15:51] <+Lucian> boobs
[15:51] <+Gears> titties
[15:51] <@Draconis> Titties.
[15:52] <+Noodle> why is this so hard?


#22 Daniel Beaver

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Posted 07 March 2011 - 08:09 PM

When Klaviel brought a chronograph to whatever Chicago war was the first week of October last fall, Ryan's Rainbowpump managed 212 fps, his AT3K 275 fps, and my 4B (after frantic pumping to equalize the OPRV a bit) 320 fps. The difference in ranges between these three guns with slug darts is not very large.


I think Klaviel's chrono may have been off-calibration that day; one of the east coast wars (Grid Core, I think?) also tested blasters with a paintball field's official chronograph, and got fps readings that were about 3/2 times what we got.

In any case, the point holds it's ground: lighter and/or less aerodynamic darts can act has limiter on....
....christ, no I'm not going to comment on that subject in a writeup thread. That would be bad form.
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#23 Nerf Gra

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Posted 07 March 2011 - 08:17 PM

Back on topic. I really like this blaster in its simplicity and effectiveness. I especaily like the stock you made it just looks so clean and well made. What sizes did you use and what did you use to blend the joints like that? It may just be the slight blur in the pictures but it looks like you used something to blend around the pipes at the joints almost like it was welded. Either way it looks awesome and hella functional.
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QUOTE(VelveetaAvenger @ Dec 6 2010, 12:14 AM) View Post

Maybe there's no Mcmaster, but you could make the first coconut airtank.


#24 PVC Arsenal 17

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Posted 07 March 2011 - 11:39 PM

@PVC: But eliminating the shell would take the fun out of it! it's true; it's not strictly necessary, but then it wouldn't be a L+LPVAT, or FOMAS. PLus, the shell is purty. I think I take your hint about discouraing new builders, but I speak from experience when I say that it's good to take challenges, just not unreasonable ones. If a new nerfer tries to make this as thier first homemamde, chances are slim, not impossible, but slim that it will come out how they want it to. They might get frustrated and drop nerfing altogether which would be a shame. I was just saying that this is probabaly a good homemade to work up to.


All fair points. The utility (and fun) of the shell is something I hadn't considered. Configuring the gun in the manner I suggested can be awkward and problematic as I've experienced on similar projects. That said, please allow me to clarify that I didn't mean to insult your work in any way. In fact I think it's a neat blend of the two main homemade gun traditions.

I'd also like to ask if you can quantify or offer comparison for the force required to retract the bolt, both with and without the mechanical advantage provided by the trigger.
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#25 NerfGeek416

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Posted 08 March 2011 - 08:03 AM

It probably wouldn't be too hard to fabricate a lever trigger, if you haven't already done so.
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