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Anti Elephant Airsoft Rifle

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: hyldgaard » Tue Nov 06, 2007 5:03 am

Mitchza89 wrote:I saw a spudder on here make a stabliser out of milk bottle plastic. He said he got the design from someone else. Anyone else know?

If the spudder you refer to is me, then this is were i got the inspiration for my darts.
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Unread postAuthor: Ragnarok » Tue Nov 06, 2007 5:20 am

jackssmirkingrevenge wrote:The effect is noticeable on commercially made airguns, though how much of a difference it would make on a homemade BB gun is debatable.

I find a large effect on accuracy from using the ported muzzle attachment I have, but that is a much larger calibre.
There is less improvement on HEAL than it was on the older Behemoth, but HEAL is more accurate in the first place from the way it passes recoil back along the barrel.

For a smoothbore with far from perfect ammo, the accuracy is far more than I could have hoped for.
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Unread postAuthor: jackssmirkingrevenge » Tue Nov 06, 2007 5:42 am

For a smoothbore with far from perfect ammo, the accuracy is far more than I could have hoped for.


Given the nature of the devices we build, we should be looking to the smoothbore muskets of old as a comparable standard of accuracy as opposed to modern rifled arms.
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Unread postAuthor: Zen/// » Tue Nov 06, 2007 9:05 am

"I can hit a 2" circle at 100 feet. "
Those milk jug darts to me sound pretty accurate.

Probably more accurate then old muskets.
(But some specialized rifled ones could kill commanders at 800yards)

This is a smoothbore http://world.guns.ru/sniper/sn46-e.htm
With fin stabilized ammo it can hit a target at 1000m
(and still penetrate 40mm of armor)

Finned/cone stabilized ammo will probably be our only way of noticably increasing accuracy. And get ever so closer to a true spud sniper's dream.....

Edit: Well if you practiced alot at the same pressure everytime you would get a feel of how far and what kind of bullet drop you will get at certian ranges. Its not like you just point and shoot. You have to be a good shot at least.... 4750fps is just crazy!!!


You aren't allowed to call this a 'sniper' until you hit a 5"x5" target at 500 yards, and even that is being generous.
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Last edited by Zen/// on Tue Nov 06, 2007 9:36 am, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Tue Nov 06, 2007 9:33 am

Zen/// wrote:This is a smoothbore http://world.guns.ru/sniper/sn46-e.htm
With fin stabilized ammo it can hit a target at 1000m
(and still penetrate 40mm of armor)


First of all, note that there are no accuracy figures given - I think this is one of the reasons that the design has not been put into production yet - because find stabilised darts are much harder to fire accurately than spin stabilised full calibre bullets.

Also:

It fires 20 gram (308 grains) tungsten dart (flechette) with muzzle velocity of 1450 meters per second (4750 fps)


At that sort of velocity (far beyond what any spudgun could ever achieve), bullet drop is almost negligible.
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Unread postAuthor: Ragnarok » Tue Nov 06, 2007 1:07 pm

Finned ammo isn't that uncommon.

I could create a finned round that HEAL could just about fire over 500 yards at an elevation of only about 5 degrees (and well over a mile at 30 degrees elevation), but there are not many "ranges" that long I wouldn't be seriously concerned about sending a chunk of pointy high sectional density steel down at half the speed of sound though, in case someone should end up in the line of fire by mistake.
HEAL lies in a quite rare class. Most low bore launchers (and most "sniper" launchers are low bore) would have difficulty in imparting as much brute force and kinetic energy into a round as HEAL can (simply because most don't use 320 psi, or in many cases, as long a barrel), so would have difficulty propelling a round out to 500 yards with a low launch angle.

But sub-MOA accuracy from a homemade launcher (most of them smoothbore) at those ranges is exceptionally unlikely. Even things like the Barrett M82 are expected to shoot not much tighter than about 2 MOA. The HK PSG 1 and the Barrett M99 can achieve 1 MOA or better, but those are high grade military rifles using match grade ammunition. (World guns is useful!)
Our standards are unlikely to ever rise above those of the military, so we have to set our sights a bit lower (there's probably a pun there).

Just because I can, I assessed the chances of hitting a 2" circle at 100 feet. For a 90% chance of a hit on any given shot, the accuracy must be at worst equivalent to 5.4 MOA. For a 95% chance, that falls to 5.2 MOA. 100% chance, no less than 5.1 MOA.
That's impressive for a spudgun, but that represents only 4% of the consistency of a 1 MOA rifle.

A 25 fold increase over that already very good figure, as well as requiring 500 yards is a nigh on impossible challenge.
So, rather than setting a test that would require a very powerful launcher to even reach the range, I suggest using this easy method to find your launchers accuracy in MOA.

The Ragnarok accuracy assessment:

Set up a round diameter target more than 10 yards away, then fire at least 10 rounds at it. The more the better.
Count the number of hits - shots that lightly clip the target are not counted, solid clips are are.

Then use this equation, remembering to use the same units for target diameter and distance to target - inches, centimetres, metres, angstroms - it doesn't matter:
Image

The answer is given in MOA.

It goes without saying that the more shots you take, this figure will become closer to the actual value of your launcher's accuracy.
Use a sensibly sized and positioned target. If you are getting 100% hits, your target is too big or too close - you are shooting better than the test can actually determine a figure for! If you want an accurate figure, use a sensibly sized target at a range where you are getting about 50% hits.
You could use an Archery style target, and count only the hits within enough rings that about half the shots are within them, using the diameter of the widest ring you are counting as your target diameter and number of hits (distance to target and number of shots will be unchanged of course)


However, that's got me interested. If I can find a suitably large range to fire down which no-one will wander across, I'll make 5 or 6 finned rounds, screw on the porting attachment, set up a large paper target and quantify the accuracy.

I used to be able to shoot 2 to 3 MOA at Cadets if they let me key the sights in properly first, almost as good as the rifles could actually do.

If I can find that 500 yard range you mentioned, and HEAL will shoot straight enough, well... we'll just see.

EDIT: Made mistake with equation. Corrected.
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Unread postAuthor: jackssmirkingrevenge » Tue Nov 06, 2007 2:08 pm

Consistency is a big issue when accuracy is concerned, more important than sheer brute force.

In this case, I would say the odds are against you at long range, as formidable as HEAL might be. For starters, IIRC you use a ball valve to trigger the QEV that triggers the piston. This means that valve opening time is potentially influenced by many variables and you'll never get a consistent velocity, even if you fill to exactly the same pressure every time.

Ammunition is a massive factor - you would have to make your rounds of consistent dimensions and weight, with the same friction in the barrel etc. Some modern smoothbored tank cannon firing APFSDS are capable of sub-MOA accuracy out to several kilometres, but the tolerances involved are tighter than the average spudgunner could even dream of.

Velocity is not as critical as consistency, but high speed certainly helps you shoot more accurately. The higher a projectile's speed, the less it will be affected by wind and gravity over a given distance. Long range weapons almost invariably fire bullets at several times the speed of sound. There are suppressed sniper weapons that fire heavy bullets at high subsonic velocities, like the WW2 Delisle carbine in 45 ACP and modern Soviet VSS and VSK-94 in 9x39mm but their effective range is well below 500 yards because of the "loopy" trajectory of slow projectiles.

I must insist on the unrifled musket example, and on those lines a Major George Hanger once put it like so:

"A soldier must be very unfortunate indeed who shall be wounded by a common musket at 150 yards and as to firing at a man at 200 yards with a common musket, you may just as well fire at the moon and have the same hopes of hitting your object."
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Unread postAuthor: Ragnarok » Tue Nov 06, 2007 5:49 pm

HEAL is piloted by a 1/2" QEV in turn triggered by a slide/sleeve valve. Not perfect consistency, but reasonable. The ball valve(s) act as safeties, nothing more. The fill pressure is probably a greater problem over the valve opening time.

Moderate round consistency isn't an issue. I've got a decent set of digital callipers, and I can be patient enough to make a round within some quite favourable tolerances, not of military standard though.

I'd be ecstatic to find that it had 5 MOA accuracy at 100 yards, that would be more than enough for me to be happy with the accuracy.

I know HEAL couldn't be anywhere near MOA accurate at 500 yards (I know 1 MOA is quite hard enough to see, let alone hit). The mere fact it would take the round 2 or 3 seconds (depends on dart size and weight) to get there would give wind or other weather a lot of time to affect it. Being accurate to within 1 degree at that range would be hard - but a 8 metre square target would be too large to set up in the first place.

If I had the opportunity, I wouldn't turn down the chance to try it.
HEAL has got to be somewhere on the list of current spudguns that could stand any chance of ever hitting a 5" x 5" target at 500 yards.
It's got the power to make that range at an acceptable trajectory, and the accuracy isn't too shabby... it wouldn't be repeatable, but it would it be an achievement anyway? Sure it would, even getting close would be impressive.

But I can do little more than just speculate on how efficiently I could get the round those 500 yards - I'd be more likely to be able to pick up a bag of rocking horse manure at the local market than find somewhere to try it out in the end.

Are there any actual approximations to put a number on the accuracy smoothbore muskets had?
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Unread postAuthor: Zen/// » Tue Nov 06, 2007 7:11 pm

"Typical musket calibres ranged from .50 to .80 inches (12.7 to 20.3mm). Depending on the type and calibre, it could hit a man's torso at up to 200 yards, though it was only reliably accurate to about seventy yards. A soldier primarily armed with a musket had the designation musketman or musketeer.

By today's standards, muskets are not very accurate due to the windage (gap) between the projectile and the barrel. A rifle bullet will spin, ensuring greater accuracy. Owing to this inaccuracy, officers did not expect musketmen to aim at specific targets. Rather, they had the objective of delivering a mass of musket balls into the enemy line. This massed-muskets approach has been likened to a "linear shotgun"."

Wikipedia
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Unread postAuthor: Hawkeye » Tue Nov 06, 2007 7:25 pm

I recently found a brass tube that is a perfect fit for arrow field points of 5/16 diameter. They glide smoothly in the barrel. I'm thinking that I can fit a small tuft of deer tail fly tying material in the hollow at the back of the points and make some seriously accurate darts for one of my 300 psi guns.
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Unread postAuthor: jackssmirkingrevenge » Wed Nov 07, 2007 3:03 am

Ragnarok wrote:HEAL is piloted by a 1/2" QEV in turn triggered by a slide/sleeve valve. Not perfect consistency, but reasonable. The ball valve(s) act as safeties, nothing more. The fill pressure is probably a greater problem over the valve opening time.


Right, my bad.

Moderate round consistency isn't an issue. I've got a decent set of digital callipers, and I can be patient enough to make a round within some quite favourable tolerances, not of military standard though.


With the right facilities, it can be done of course, but you'd have to make enough rounds to be able to calibrate your scope, so throw in lots of time and patience too :)

I'd be ecstatic to find that it had 5 MOA accuracy at 100 yards, that would be more than enough for me to be happy with the accuracy.


From here - "A smoothbore "slug gun" with rifle sights will usually shoot groups in the 3" (6 MOA) range at 50 yards/meters" - I'm guessing homemade projects at lower velocity would fare worse.

HEAL has got to be somewhere on the list of current spudguns that could stand any chance of ever hitting a 5" x 5" target at 500 yards.


It's high on the list but at subsonic velocities, you don't need a telescopic sight, rather something like this:

Image

With my 900 fps 28 ft/lbs air rifle I have to aim several feet higher in order to hit a target at 120 yards.

Are there any actual approximations to put a number on the accuracy smoothbore muskets had?


Figures vary - particularly as due to the problems caused by propellant fouling in extended use, musket balls tended to be made slightly smaller than the calibre leading to the "golfball in a drainpipe" effect of the ball leaving the muzzle at an unpredictable angle - but it's safe to say that relibly hitting a man sized target at 100 yards was considered extremely accurate shooting.
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Unread postAuthor: Novacastrian » Wed Nov 07, 2007 3:32 am

What's with the Bayonete on the end of a air rifle?

Edit: oops my bad, is that 7.62?
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Unread postAuthor: jackssmirkingrevenge » Wed Nov 07, 2007 4:16 am

Novacastrian wrote:oops my bad, is that 7.62?


Yep, it's a Yugoslavian produced version of the Russian SKS 7.62x39mm carbine.

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Unread postAuthor: Ragnarok » Wed Nov 07, 2007 9:12 am

5 MOA would be more than I'd expect. Hitting within 10 MOA would still be very good as far as I'm concerned.

I'll experiment at 100 yards if I find the time, as there are enough places to manage that around where I live, but if I ever remember a relative with a very long field, a long range shot or two would be fun.
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Unread postAuthor: jackssmirkingrevenge » Wed Nov 07, 2007 9:30 am

As far as I'm concerned, if you can reliably hit a 45 gallon drum at 100 yards and still put a hole through it (which shouldn't be much of a chore for a nail dart) then you have a spud launcher to be truly proud of :)
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