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300-350 fps mini combustion sniper

Built a combustion 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: THUNDERLORD » Sun Nov 30, 2008 11:28 am

Tsukiten wrote:Yeah I made it because I just had the parts around. But the concept works so I might as well make some high-quality one some day.


Good job!
I'd love to see the next version.
Although as it is there you don't have to worry about looking like a guy with a "real" sniper rifle.
Looks like a lot of fun. :)

I hope to build a butane+ N2O hybrid with a chamber about the same volume. But I'll probably have to find the right mix using some type of constant spark gap and some trial and error. 8)
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Unread postAuthor: Ragnarok » Sun Nov 30, 2008 12:31 pm

I like it. It's semi-ghetto, but it's functional ghetto.

I'd be more than a little surprised if your groups are quite as tight as you claim. How are you measuring them? And how many shots are you firing, and at what exact range? Oh, and I suppose, indoors or outdoors - because that's quite a significant difference, with wind and all that.

I can't exactly say "looks good", because like I said, it's a bit rough and ready - but the damage is impressive enough.
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Unread postAuthor: starman » Sun Nov 30, 2008 12:48 pm

Just a few comments:

I'm not a pill bottle fan, I'm not sure why others are... :roll: That being said, I do like your barrel length...you're extracting a lot of efficiency out of that pill bottle with your barrel alone.

The tie wraps are an improvement over duct tape certainly...if you painted your stock black and used black tie wraps, they wouldn't stand out nearly as much.

Your "slight bend" hop up will cause unnatural barrel wear. I would straighten it.

As others have noted, the stock could use some more finish work.
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Unread postAuthor: that_guy » Tue Dec 02, 2008 9:44 am

combustion or pneumatic
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Unread postAuthor: Ragnarok » Tue Dec 02, 2008 11:29 am

that_guy wrote:combustion or pneumatic

Um, in the Combustion cannon show case and even named as a combustion in the topic title?

You're a shoo in at the world inattentiveness awards, you are.
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Unread postAuthor: starman » Tue Dec 02, 2008 11:41 am

Ragnarok wrote:You're a shoo in at the world inattentiveness awards, you are.


He's been leaving kicked-up post droppings all morning, just like this.
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Unread postAuthor: Tsukiten » Tue Dec 02, 2008 2:56 pm

Oh wow thanks for the replies guys! :D

Ragnarok wrote:I'd be more than a little surprised if your groups are quite as tight as you claim. How are you measuring them? And how many shots are you firing, and at what exact range? Oh, and I suppose, indoors or outdoors - because that's quite a significant difference, with wind and all that.


The shots to check the groups were all done indoors, and I kept shooting on some paper with squares on it. I marked, for example, a square (1 cm x 1 cm) and tried to shoot it. Next I would check how far it was from the marked square. These were done at like 7.5 yards distance and were all placed in like the center of the square, sometimes slightly out of the "lines" of the square. But I preferred writing "0.5 inch groups at 15 yards" than "1/4 inch groups at 7.5 yards". I didn't take alot of shots to test consistency/accuracy. Just about 15-20.
And if I tried to fire outdoors, you could see the bb's fly bloody straight. I tried to shoot some leaves that stood out (up to 10 yards) and some metal chimney on the other side of the street (25 yards away or so, about 4 inches in diameter) and I managed to hit them all (I checked for holes in the leaves with binoculars and I heard the *ping*-sound from the metal chimney.

What really sucks is that, because the scope is fixed with those "plastic strap things", you pretty much have to check if the scope is on aim every shot...so if you do that part wrong shots may be off, alot...
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Unread postAuthor: Ragnarok » Tue Dec 02, 2008 3:40 pm

Tsukiten wrote:Next I would check how far it was from the marked square. These were done at like 7.5 yards distance and were all placed in like the center of the square, sometimes slightly out of the "lines" of the square. But I preferred writing "0.5 inch groups at 15 yards" than "1/4 inch groups at 7.5 yards". I didn't take alot of shots to test consistency/accuracy. Just about 15-20.

Ah... I see.
You're misunderstanding how these things work.

When talking about grouping size, it has to count the total spread of shots from one extreme to the other - not just how far it has hit from where you wanted it to.
This essentially makes your groups twice the size you claim them to be.

It's also not proper to scale the range and group size - 1" groups at 15 yards are not the same thing as 1/2" groups at 7.5 yards, the former is more difficult to achieve, because of instabilities in projectiles.

It's not bad accuracy even so.
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Unread postAuthor: Tsukiten » Tue Dec 02, 2008 3:44 pm

Ragnarok wrote:When talking about grouping size, it has to count the total spread of shots from one extreme to the other - not just how far it has hit from where you wanted it to.
This essentially makes your groups twice the size you claim them to be.

It's also not proper to scale the range and group size - 1" groups at 15 yards are not the same thing as 1/2" groups at 7.5 yards, the former is more difficult to achieve, because of instabilities in projectiles.


Oh yeah crap I forgot that step...the number I get is only the "radius", right?
And yeah changing the '1/2" groups at 7.5' yards to '1" groups at yards' isn't really correct I know...The projectile is likely to go in a curve than in a "slightly-off-center-straight line".
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Unread postAuthor: Ragnarok » Tue Dec 02, 2008 3:52 pm

Tsukiten wrote:Oh yeah crap I forgot that step...the number I get is only the "radius", right?

Essentially, yes.

Really you should shoot about 10 shots, then measure across the extremes for an answer, but you can estimate it as you've done, assuming your sight is properly dialed in.
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Unread postAuthor: that_guy » Wed Dec 03, 2008 9:25 am

no wich is better
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Unread postAuthor: Ragnarok » Wed Dec 03, 2008 9:56 am

that_guy wrote:no wich is better

Why are you asking these things here?!?! How on earth was anyone supposed to guess that question from "combustion or pneumatic" in a showcase thread?

To avoid an argument - they're good for different things. In my opinion:
If you want Big or portable, go combustion
If you want Power or compactness, go pneumatic.
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Unread postAuthor: Cosmic Muffin » Wed Dec 10, 2008 5:19 am

i have one of those telescope things.
they are good if you are planning to shoot it upside down :lol:
it messes with your mind, like you go to move the gun up, but your mind is telling you to move it down :?
nice gun,
the stock is an engineering marvel XD
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Unread postAuthor: Tsukiten » Thu Dec 11, 2008 2:23 pm

Cosmic Muffin wrote:i have one of those telescope things.
they are good if you are planning to shoot it upside down :lol:
it messes with your mind, like you go to move the gun up, but your mind is telling you to move it down :?
nice gun,
the stock is an engineering marvel XD


"engineering marvel"...hell yeah xD
And yea those scopes are something you gotta get used to but after you do, it's not that confusing anymore :D
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Unread postAuthor: dart guy » Thu Jun 13, 2013 5:35 am

i think that of you epoxy the stock together it would look better than with the zipties and i also think you could make a pvc outer barrel but in a half or 5/8 section and put masking tape around the barrel to fit it under the pvc then fasten it with som screw on clamps and i also think you should look into making a break bearel acton for quicker loading
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