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Spring Piston Air Rifles

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: Ragnarok » Wed May 06, 2009 3:34 pm

@ maverik94: If you really really insist, but it'll be your loss, not mine.

I don't think you've quite grasped the sturdiness and precision that needs to go into engineering one of these things to actually get anything out of it at all though.
Seriously - my TX 200, at a very modest 11 ft-lbs, has to be built so sturdily that it weighs more than HEAL - which is upwards of 300 ft-lbs.

The precision machined springer with a large company's design budget and multiple engineers working on it for years is heavier, but less than 4% of the power of what a jobless high school student threw together in his backyard over a weekend using parts from the local DIY and absolutely no blueprints whatsoever.

Okay, it was me that built HEAL, and I'm just awesome... but I think that illustrates the serious disjoint between the difficulty of manufacturing a springer and that of manufacturing a pneumatic.

Springers are not a good amateur project.
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Unread postAuthor: maverik94 » Wed May 06, 2009 3:38 pm

yeah, All I want to make is a rifle that will not need to be connected to a pump, pumped up, shot, etc.......... The spring piston is the only kind of rifle that doesEDIT: Wai, what abou SINGLE action air rifles....now THATS an idea. you only have to pump once, then leand and fire and repeat....
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Unread postAuthor: MountainousDew » Wed May 06, 2009 3:48 pm

Go buy a nerf gun...
They are inexpensive, don't need to be pumped to shoot, and you can mod them for more power.
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Unread postAuthor: maverik94 » Wed May 06, 2009 3:57 pm

uhhhhh....no, I'm not into nerf guns, nor am I into not building my stuff.
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Unread postAuthor: Ragnarok » Wed May 06, 2009 4:15 pm

You'd still be better off spending the money on a cheap commercial springer. It'll almost certainly be cheaper, safer, more powerful and more accurate than what you'll be able to come up with - no offence intended, but sometimes it's not a good idea to go DIY.

maverik94 wrote:The spring piston is the only kind of rifle that does this.

Not really. It's perfectly possible for pneumatics to get more than one shot out of a single fill, like Brian the Brain's recent projects - or to have a built in gas bottle. Or like you say, single stroke pneumatics.

Now, I'll admit that I am trying to design something that works on the self contained criteria, but I'm not walking the beaten track for this one...
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Unread postAuthor: jackssmirkingrevenge » Wed May 06, 2009 10:37 pm

maverik94 wrote:But then how do commercial air rifles shoot .177 slugs at 1200 fps?


The high velocities are marketing tools, manufacturers commonly use unfeasibly light pellets to achieve magic fps figures that are irrelevant in the real world. Anyone who knows what he's talking about will want to know the weight of that slug and therefore the muzzle energy.

An airsoft BB at 1500 feet per second for example sounds fantastic, but at only 0.12 grams this not only means a relatively low muzzle energy of around 9 ft/lbs but also very short range as velocity will drop off very quickly.

A typical 1 gram 0.22" lead pellet at just 750 fps, half the above velocity, on the otherhand will have double the energy - around 20 ft/lbs - and retain that energy out to a much longer range.
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Unread postAuthor: Ragnarok » Wed May 06, 2009 11:09 pm

jackssmirkingrevenge wrote:Anyone who knows what he's talking about will want to know the weight of that slug and therefore the muzzle energy.

Generally, you can expect their technique is vaguely equivalent to:
Find the lightest pellet possible (6.5 grains in .177" wouldn't surprise me), fire 10 shots over a chrono, take the highest velocity, add 5% more on top for good measure, look at the claims made of other rifles in the same price range claim, if short of other manufacturers claims then add another 5%.

That's part of the silver lining to the UK's airgun law. Because everything is limited to ~12 ft-lbs at most, nobody gives a crap about velocity, so you don't get these repeated wild claims about "feet per second".

No, instead, they lie to you about how many shots you get out of a PCP fill. :roll:
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Unread postAuthor: jackssmirkingrevenge » Wed May 06, 2009 11:51 pm

Ragnarok wrote:That's part of the silver lining to the UK's airgun law. Because everything is limited to ~12 ft-lbs at most, nobody gives a crap about velocity, so you don't get these repeated wild claims about "feet per second".


True. Another interesting point that no one seems to exploit is that since the limit is on energy, one can legally make a high velocity airgun using a smaller calibre - say 3mm - that would be useless for hunting but when it came to target shooting would give a much flatter trajectory.

No, instead, they lie to you about how many shots you get out of a PCP fill. :roll:


Well, they have to lie about something ;)
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Unread postAuthor: Ragnarok » Thu May 07, 2009 12:19 am

jackssmirkingrevenge wrote:Another interesting point that no one seems to exploit is that since the limit is on energy, one can legally make a high velocity airgun using a smaller calibre

There's quite some good reasons why no-one does.

Aside from the fact that .22" air rifles tend to outsell .177" at something like a 4:1 ratio (at least according to Webley), 0.177" is already hanging around 800 fps in light pellet weights. If you start going past 800-900 fps, you start to lose accuracy.

Also, bear in mind, a 3mm airgun would be rather fiddly to load, and not being able to use it for hunting would put a lot of people off.

The real clincher however is that creating rifled barrels any smaller than 4.5mm is very very tough to do. Basically, .17 calibre is as small as rifled barrels can really get with current technology, although if Ben Garzy's new rifling technique can really come through*, there is the potential for things down to perhaps 3mm bore, but it'd be a while before pellets were manufactured.

*Although there is a lot of BS and hype surrounding them, claiming all kinds of crap that there is no way that the barrels can deliver.
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Unread postAuthor: jackssmirkingrevenge » Thu May 07, 2009 1:42 am

I was thinking 3mm precision bearings in a very tight fitting smoothbore barrel, a springer would easily take them past the speed of sound and accuracy should be reasonable, but as you say it would be a purely academic airgun.
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