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Why pyrodex should be ok with the batfe for use in spud guns

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Why pyrodex should be ok with the batfe for use in spud guns

Unread postAuthor: Joe470 » Sun Oct 02, 2011 7:01 pm

Spud guns aren't intended to be weapons.
One could argue that flare guns, model rockets, rope throwers, and powder primed nail guns, even decoy throwers for retriever training that use 22 blanks like nail guns fall into the same category.

[removed by moderator]

Of course if you make a cannon out of plastic you CANT expect velocities over a couple, maybe a few, hundred feet per second. and I WOULDN'T use ANY kind of metal projectile.

[removed by moderator]. Thats a no-no. However, a spud gun is not a fire arm. Not where I live at least.


[removed by moderator]

Have you seen a lot of plastic rifles lately? I doubt anyone can or would argue that a potato flying at 300 fps is a good weapon. Its a toy, like a BB gun, that could cause harm or even, in rare instances, death if used inappropriately.

Yeah, you could pretty easily make a bad ass cannon out of steel that would shoot ball bearings... bla bla bla. If you do that you're going to jail, not because you broke the law, but because you're probably up to no good.

So I don't want to hear alot of crap like "you're a criminal" or "youre going to hurt someone" or "why would you want a repeating spud gun that shoots accurately, and predictably every time you cycle the action and pull the trigger"


I've posted here before and was yelled at and ousted like some kind of heretic in the 1700s. Basically, because people thought I was advocating illegal or dangerous activity.
From what I understand, [removed by moderator] From experience I can tell you with confidence that it is SAFER than propane guns for alot of reasons. Here are a few;

1, very little risk of burns. primitive spud guns have burned me before.
2, they are more dependable. While I WOULDN'T be the guy on youtube that looked down the barrel and about blew his head off...... there is a guy on youtube that looked down the barrel and about blew his head off.
3, more accurate. I doubt you'll shoot when there is a possibility of hitting a person. More accurate fire is safer for property, and its not as messy.
4 can be ignited via electric current from a safe distance
5 [removed by moderator] What is a half load of propane? consistent fire depends on the same charge repeatedly. Reducing your propane charge reduces its ability to ignite.



[removed by moderator]

I don't know what you call the fatter part you spray fuel into. I call it the compression chamber.

[removed by moderator] I think its legal. If someone can show me that it isn't, according to the rules published on the ATF website, i wont do it anymore.

Until then, i'm going to keep shooting spuds and golf balls for my dog to chase. Since I could hit a basketball with a golf ball at a hundred yards repeatedly once im on target, im kind of pleased with it.
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Unread postAuthor: ramses » Sun Oct 02, 2011 7:27 pm

The intent of the rule is to completely separate what we do here from firearms. The media and other ignorant people may see black powder and PVC spudguns, and get this site shut down.

What you propose is probably effective, and probably reasonalby safe, but there are two big issues with it (besides the above) that, when combined, can be dangerous

1. it is easy
2. more fuel will produce more power.


This is in contrast with all the spud guns here. To get above a basic combustion, you have to make the whole thing air tight, pressurize the fuel mix, and add a valve/ burst disk. This is called a hybrid, and to be completely honest, they're kind of a bother to build, debug and use. They require an understanding of the mechanism in order to be useful. They're somewhat idiot proof.

Pneumatics are the same way. Most air compressors only go to about 150 PSI. To exceed that, you need to either use a shock pump, build a hand pump, or build a rig to use bulk gas cylinders. It's not as trivial as simply adding more pyrodex.

With the powder, someone could use 75 grains, and shoot a potato 200 yards. This may be perfectly safe. Now they want more power, and use 300 grains. BOOM. More power was produced, but it was too much for the launcher. With a standard combustion, more fuel will reduce performance until the launcher no longer functions. This is sort of a governor for all the people who screw around with their friends (and maybe alcohol or other drugs). If they were using powder, one person could easily say "Lets put all the powder in at once and see what happens." Or they could mix up grains and grams when weighting out charges.


One major accident that can be connected to this site could get PCGuy in trouble, and could get the hobby legally banned.
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Unread postAuthor: Fnord » Sun Oct 02, 2011 7:40 pm

(^ninja'd by ramses. oh well.)

Properly done, yes, you can use a small BP charge in a pvc-pipe gun, provided you really, really know what you're doing.
The reasons why we don't do it are:

People could come here without reading exactly what we're doing, then assume it's safe to go ahead and put half a pound of charge in and kill themselves. It's happened before.
I don't have any problem with natural selection but in this case the idiots get us tons of bad media attention.

Another reason; if you're looking for power and repeatability you can't beat a piston-valved hybrid design. Crowley and SB15's cannons may be capable of muzzle energies in 4-gauge shotgun territory. I'm not sure I would trust a BP cannon made of plumbing pipe used for that type of power.


Lastly, BP is dirty as hell. Right now there is not a gun on this site that has to be cleaned out regularly (maybe with the exception of hair-spray cannons and those who shoot excessive amounts of potatoes... starch does accumulate over time).

Its a toy,

No, it's not. And I'm pretty sure BB guns all say THIS IS NOT A TOY on the side.

edit... also, just to add, it's fairly easy to get something like a golfball traveling over a few hundred fps. I had a very modest advanced combustion that did about 430 fps reliably with not much variation. This could easily kill you.
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Unread postAuthor: saefroch » Sun Oct 02, 2011 8:07 pm

You agreed to the rules before posting. You clearly don't agree with them.

WHY ARE YOU POSTING?????

Joe470 wrote:1, very little risk of burns. primitive spud guns have burned me before. 2, they are more dependable. While I WOULDN'T be the guy on youtube that looked down the barrel and about blew his head off...... there is a guy on youtube that looked down the barrel and about blew his head off.
3, more accurate. I doubt you'll shoot when there is a possibility of hitting a person. More accurate fire is safer for property, and its not as messy.
4 can be ignited via electric current from a safe distance
5 the charge can be adjusted precisely to allow for the slowest shots while remaining effective. If you want to let your friends shoot it, put in half loads. What is a half load of propane? consistent fire depends on the same charge repeatedly. Reducing your propane charge reduces its ability to ignite.


1) If you want to argue based on anecdotal evidence, it must be true that there is far more risk for burns from a black powder-like substance than there is from a combustion. I've never burned myself on a combustion spudgun, but solid propellants are another matter altogether.

2)They are no more dependable. Just as you measure out your propellant in this case, use of a fuel metering system results in a highly dependable launcher.

3)The accuracy of a projectile is not affected by what produced the force behind it.

4)All gas-powered combustion cannons can use an electric ignition system, many kinds have been discussed and used, nearly every type imaginable is mentioned on the forums.

5)False. A heavy or light mix results in less power, anyone who's ever experimented with different mixes is fully aware that it's not very difficult at all to produce a mix barely capable of expelling a 10g projectile from a 3' barrel.
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Unread postAuthor: DYI » Sun Oct 02, 2011 8:07 pm

I don't think any sane member here will argue that what you propose is illegal, objectionable, or even dangerous in the hands of someone who is sober, safety minded, and has a basic understanding of what he's doing. We don't hate solid propellants guns, and I'd be willing to wager that a pretty good chunk of us make things similar to what you describe, or even full-fledged BP guns. I'll also add that I find your assumption about people who make "badass" solid propellant guns to fire metal projectiles offensive. Several respected, longtime members of this forum do just that, and not one of them has ever harmed or intended to harm anyone with them (they haven't gone to jail for them either :wink: )

I feel a short discussion of your numbered points in favour of combustion spudguns converted to BP is in order.

1) BP has a *much* higher energy content per unit volume and produces solid combustion products. Propane doesn't even begin to compare in terms of burn hazards. Put your hand on a small heap and light it to see for yourself.

2) A simple metered propane combustion with a fan will, inside its operational temperature range, have a lower rate of misfires than a modern firearm, and those will be caused by lack of preventative maintenance on the gauge, regulator, ignition system, and fan power system. If one builds things so half-assed that they often fail to fire, he should not attempt to alleviate his reliability issues by moving to solid propellants.

3) More accurate? They'll be almost totally identical in internal ballistics, apart from the BP gun being somewhat less efficient. Also, the commonly used HV pulse ignition in propane guns (which is relatively difficulty in solid propellant guns) makes ignition timing more consistent. Which, if anything, improves accuracy.

4) So can propane... Or hydrogen, or methane, or RDX...

5) Can't argue with that one. Problem is, as the above posters have identified, it's also possible to ramp up to "much too much" propellant, and give us all a bad name.


What you're doing is perfectly safe to do, it's probably totally legal where you live, and it's a fine idea. However, as ramses and Fnord have already stated, we don't allow discussion of solid propellants here because they're an easy way for idiots to blow themselves up. Typically, by the time you can build a pneumatic or hybrid energetic enough to kill you if it goes wrong, you know an awful lot about how to build them so that they don't go wrong.

We're not calling you an idiot for doing what you do, but there's a very strong argument in favor of continuing to not discuss solid propellants on this forum. If you're itching to discuss solid propellants, you'll often find several knowledgeable folks in the chat room who'll be all too happy to oblige.


Edit: also ninja'd... :lol:
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Last edited by DYI on Mon Oct 03, 2011 6:37 am, edited 1 time in total.
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Unread postAuthor: Mr.Sandman » Sun Oct 02, 2011 10:02 pm

Enjoy your very brief visit with us at spudfiles, I'm sure you're on your way to receive the Darwin Award. If you would have read the rules before you posted, you would have been aware that this topic violates the whole "No solid propellants discussion" rule.
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Unread postAuthor: Crna Legija » Sun Oct 02, 2011 11:50 pm

tl;dr
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Unread postAuthor: Insomniac » Sun Oct 02, 2011 11:50 pm

While I don't agree with you on all points, I can see some of your logic and won't argue them, having nil experience with solid propellants myself.

The primary reason for not discussing them, as other members have pointed out, is the self-limiting nature of gasous propellants. You sound intelligent enough so I'm sure you can see the fundamental difference between the two systems: Gaseous propellents depend on the correct fuel air mix, so at atmospheric pressure you simply can't overfuel a launcher and have the launcher destroy itself. Too much fuel, no ignition. Spudguns are designed to operate exclusively at the ideal, maximum energy fuel/air mixture. If you do the fuelling horribly wrong, the worst thing you get is a failure to ignite.

Solid propellents have an inherent danger in that you CAN use too much, and it will ignite and will cause a dangerous explosion. In the right hands this will never happen, but it's too risky to associate spud-guns with solid propellant cannons, at least on a public forum.
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Unread postAuthor: Zeus » Mon Oct 03, 2011 3:36 am

Mods, <b>please</b> allow this fellow to reply to the topic before this is locked and he is banned.

I concur with DYI too.
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Unread postAuthor: jackssmirkingrevenge » Mon Oct 03, 2011 4:54 am

The responses here indicate a common understanding of why discussion of solid propellants is not allowed on this forum, however awesome it might be in terms of power potential, and how safe it might actually be if used responsibly.

Personally, my quest for a small cartridge loaded automatic would be rendered much easier by the use of solid propellants, but there's something about using compressed air and burning propane, something "clean", and I personally enjoy the challenge.
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Re: Why pyrodex should be ok with the batfe for use in spud

Unread postAuthor: Hotwired » Mon Oct 03, 2011 11:22 am

Joe470 wrote: If someone can show me that it isn't, according to the rules published on the ATF website, i wont do it anymore.


Not the issue though is it.

You think you're being harassed unfairly because you don't believe it to be illegal.

The fact is you completely failed to read the rules of the forum, one of which is no solid propellant.

The forum doesn't dictate what you do, just what you're allowed to discuss on it.
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Unread postAuthor: MrCrowley » Mon Oct 03, 2011 1:22 pm

Your post ain't what it used to be.

Sorry, but we have rules on this forum.
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Unread postAuthor: Technician1002 » Mon Oct 03, 2011 1:23 pm

In regards to primers and spudguns the rules prohibit using powder as a Propellant. If you use a muzzle loader black powder primer to set off a propane air combustion it should be OK as the primer is not the propellant. The primer should be small enough that the primer alone can not eject the spud from the barrel to remain within the rules. Anything beyond using a cap primer would be pretty much beyond the scope SF is designed to be.

Along those lines, has anyone tried using cap gun caps for ignition of a combustion spudgun?
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Unread postAuthor: cammyd32 » Mon Oct 03, 2011 2:43 pm

1, very little risk of burns. primitive spud guns have burned me before.
+1 http://www.spudfiles.com/forums/viewtopic.php?p=332355&sid=81bf2070203062f2aaf13a23ba8f8ada#332355 - my big post on this page
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Unread postAuthor: Hotwired » Mon Oct 03, 2011 5:55 pm

cammyd32 wrote:
1, very little risk of burns. primitive spud guns have burned me before.
+1 http://www.spudfiles.com/forums/viewtopic.php?p=332355&sid=81bf2070203062f2aaf13a23ba8f8ada#332355 - my big post on this page


Seriously, what is this I don't even...

It's not the responsibility of the cannon to get your hands out of the way of the blast of flame. If you put together a cannon properly there should be no question at all of being in danger of burns.
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