2.4kpsi helium powered BB gun - build log

[Hotwired]

Besides, do you really want a drunken machinist to make you a very high pressure valve?

[Novacastrian]

We do it all the time at our shop, a customer will ask if we can do a small job or they need a small amount of material and we give them the option of paying in cash or beer. The last bloke wanted 12 polyurethane washers and was quoted 216$ at another place, we were able to supply them the same day at the princely sum of a carton of beer!

The reason why i think it will work is that the bloke that does the job is getting paid to be at work anyway, so a couple of bottles of fire water would be a very nice bonus

I can just imagine when i take control of the workshop, there will be empty beer bottles everywhere and a very upset accountant

[Ragnarok]

I can just imagine when i take control of the workshop, there will be empty beer bottles everywhere and a very upset accountant

Well, maybe the accountant could recycle the empties to make up some of the difference.

Still, I have to worry about what would get machined.

[Skywalker]

Holy smack man! Tell me about your helium supply? What size bottle, what pressure, how many shots might you get, will it cost you an arm+leg?

What made you decide to build this?

[DYI]

The helium supply will be obtained after it has been found to seal perfectly with my existing nitrogen supply (which has a far larger effective particle size, and therefore doesn't leak as readily as helium).
The helium tank will be the same type as my nitrogen tank. The specs won't mean much to you, as they vary by companies. I use AirLiquide for my compressed gas supply, in combination with some Praxair parts.

For what it's worth;
Tank type: Type 16 industrial helium
Capacity: 91 cubic feet @ 1atm
Pressure: 2,492 psi

I pay $56/year to lease the tank, and it remains the property of AirLiquide.

The volume of the tank is around 900 ci, while the volume of the chamber is going to be about 5 ci. The chamber will be filled directly from the tank, so I should get a lot of useful shots before having to refill the tank, as the performance will be respectable even when the pressure drops to 1kpsi.

I decided to build this mainly to have a gun that would be fun to shoot. It should be about as accurate as a musket, if not slightly moreso (that is, accurate up to about 80 yards or so), and it will have fairly high power for it's caliber.

Due to Canadian airgun laws, I'm going to have to get this thing certified by a gunsmith, and then get a license for it, which shouldn't be too difficult, as it classifies as a muzzle loader. I don't anticipate any problems in that aspect; the safety margins in the design are huge, leaks with nitrogen will be non-existent, it has a built in trigger lock, and can't be charged or fired without understanding its exact operation.

[ALIHISGREAT]

I decided to build this mainly to have a gun that would be fun to shoot. It should be about as accurate as a musket, if not slightly moreso (that is, accurate up to about 80 yards or so), and it will have fairly high power for it's caliber.

Due to Canadian airgun laws, I'm going to have to get this thing certified by a gunsmith, and then get a license for it, which shouldn't be too difficult, as it classifies as a muzzle loader. I don't anticipate any problems in that aspect; the safety margins in the design are huge, leaks with nitrogen will be non-existent, it has a built in trigger lock, and can't be charged or fired without understanding its exact operation.

i think 80yards is a bit of an underestimate with nice consisten ammo i would expect at least 100yards from a beast like that although this could be increased alot by a small amount of hop-up which would give the ammo consisten spin every shot and therefore increase accuracy.

and what happens if the gunsmith won't certify it? you will carry on regardless right? so why get it certifyed? or do the police go round to everyones houses in canada and look for illegal homemade guns and whip out their chrony and scales to test them? i can see advantages of having a liscence for exampe you may be able to take it to a gun range or something and if the police do ever turn up you can just whip out the license but my guess is that it will never happen so in my eyes licensing is a waste of time (and money?)

[Ragnarok]

Due to Canadian airgun laws, I'm going to have to get this thing certified by a gunsmith, and then get a license for it, which shouldn't be too difficult, as it classifies as a muzzle loader. I don't anticipate any problems in that aspect; the safety margins in the design are huge, leaks with nitrogen will be non-existent, it has a built in trigger lock, and can't be charged or fired without understanding its exact operation.

But of course, fools are so creative - foolproof is nearly impossible. Still, best of luck with that.

@ALIHISGREAT: Now that would be fun if I could get a licence for my spudguns - taking them to one of the UK's few gun ranges:
"Right, what are you bringing onto the range today......"

There would be a certain amusement from watching other people load up with conventional ammunition while I was cutting cylinders from potatoes.

[DYI]

I won't really mind if I can't get it certified, I'll just have to be a bit more careful with it. The fact that it isn't going to look anything like a weapon will help me if I can't do it the legal way, but I prefer to keep my hobby as legal as is possible. I'm not interested in giving spudding a worse reputation than it already has.

Due to the lower projectile mass, the barrel which is at least .006" too big, and the fact that the planned setup prevents me from using a hop up, I don't expect accuracy much better than that of a musket, if at all. If you read the figures I quoted though, ammo consistency will be higher than that found in conventional firearms, what with the 1/10,000" tolerances and all.

@Rag: From my limited knowledge of UK gun laws, registering HEAL would be about as likely as the pet pterodactyl I mentioned in the "cloud" thread today.

[VH_man]

.006 inches is like, nothing.

with that kind of tolerance, i seriously beleive that your going to get some serious accuracy.

hell, with an Airgun .177 cal BB i can consistently pop over a soda can from 100 feet away with my air rifle. And if your using Steel BB's, wich are farrrr more consistent than .177 cal airgun BB's, your going to get some riddiculous accuracy.......

i think Mcmaster has .251ID stainless steel pipe and .25" diameter Steel Bearings, wich come in a pack of 500. both have a tolerance of .0001, so youd be safe, and all BB's would fit with such precision that the accuracy youd get would be unimaginable.

but bah, my airsoft gun can put 15 BB's in a one inch circle at 80 feet, i dont see why you wouldnt be able to.

[DYI]

If you didn't read the last page, I will requote: The tungsten carbide ball bearings that I will use are .25", +/- .0001".

I'm not getting new tubing, because this length cost ~$40 to ship McMaster---> Georgia-----> Parry Sound----> My house, which is the most direct route, and because at least half of the bearings wouldn't fit .25" ID tube.

And I expect accuracy at almost 300 feet. Maybe not popcan puncturing accuracy, but decent accuracy.

[Ragnarok]

@Rag: From my limited knowledge of UK gun laws, registering HEAL would be about as likely as the pet pterodactyl I mentioned in the "cloud" thread today.

Well, you obviously don't have a time machine then, but pterodactyls aren't my choice of pet.

VH_man has a point, 0.006" is a pretty tight gap, far closer than muskets of old will have achieved. I reckon you should be able to do quite a bit better than a musket in terms of accuracy, although you are unlikely to put rifled firearms to shame.

[VH_man]

I say someone needs to make a rifling machine........ hey, mabey ill do it (grins.....)

ill post some plans. ive been inspired by my air rifle's ability to pop over something the size of a walnut from nearly 100 yards.................. i just gotta have a rifled barrel that shoots .50 cal/bigger ammo!!!!

[jackssmirkingrevenge]

With those parts and pressure at my disposal, I'd be more inclined to make a the cloud BBMG from hell...

[c19o]

With those parts and pressure at my disposal, I'd be more inclined to make a the cloud BBMG from hell...

Same here.

[TwitchTheAussie]

Like 2 bottles of Whiskey or 2 Cartons of beer for his services, chances are a thirsty bloke that has just finished work will take you up on your offer, saving you about 100bucks in the process.

That might work - but only if you are old enough to acquire such beverages.

I can't recall how old DYI is, nor do I know the Canadian drinking age, but I do know that most people couldn't pull off said trick.

You sir, Have not met enough aussie labourers .

With those parts and pressure at my disposal, I'd be more inclined to make a the cloud BBMG from hell...

Ditto. Though a nice single shooter with tungsten carbide bb's. Hmmm Damage control will have their hands full with cans and bottles.