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Golf Ball Rifle with Rotating Breech Loader and Bipod

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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Golf Ball Rifle with Rotating Breech Loader and Bipod

Unread postAuthor: williamfeldmann » Mon Aug 11, 2008 2:56 pm

I got this guy built last fall late enough I only had time for a few test shots with it last year. This year I have gotten my ranging down and with a full load of 150 psi I can clear a little more than 400 yards. I am currently working on a sighting apparatus of some sort since I can eyeball aim it to hit a trash can lid at around 100 yards. I am going to be building a smaller and more maneuverable (read as not 7 feet long and heavy as hell) in time for a family get-together this Labor Day, so, I thought I would upload my "new" big gun before posting the smaller guy when I get it built. The barrel is sleeved 1.5 inch class 200 (SDR 21) inside and 2 inch sch 80 electrical conduit outside (conduit is non pressurized and so much much cheaper). The tank is just 2 inch sch 40. They are both 5 feet long. The valve is a 1 inch Rainbird CP-100 valve that is modded to pneumatic activation, you can see how I did that in this thread.

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The rotating breach is from a rough design that I saw on here quite a while ago and can't find anymore. It is a 2 inch tee that is not glued in place but rotates around the barrel which runs through it. The tee rotates quite easily when sanded a bit on the inside and when flipped to the side completely closes the breech for minimal air loss. You could mount a chunk of 2 inch pipe on this tee as a clip and I may do that in the future with a more quickly pressurized gun. :) The pic is a little dark but you are looking all the way down into the bottom of the barrel. The ring forward of the tee is half of a coupler that is glued in place to keep the tee in place

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The bipod is Harris Ultralight rifle bipod. They cost around $65 from Cabelas. There are cheaper brands and models out there and I would suggest those. I had this one available since I use it on both of my hunting rifles. The Bipod mounts to a "swivel stud" You can get these at any sporting goods store or Walmart even. They are for mounting a sling or bipod on. They require a small pilot hole and then the stud just screws in. Only about 2 minutes of work to put in a stud and mount the bipod, and makes a real nice stand for a stand alone gun like this.

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Unread postAuthor: Floyd » Mon Aug 11, 2008 3:07 pm

Looks great! I'm always ready for damage pics.

How is that valve working? I heard somewhere that they don't open fast enough. I think the person may have just done a crappy job modding it.
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Unread postAuthor: MaxuS the 2nd » Mon Aug 11, 2008 3:18 pm

Wow, very nice spudgun. Really well done, especially with the bipod and stock.


Trooperrick, they work quite well when modified. The speed of acuation depends solely on the flow coefficient of the pilot valve. The larger the coefficient, the faster the sprinkler valve will open.
That's why ball valves work better than the solenoids that they come with.
So if it's not opening fast enough - but has been modded, then the pilot valve used did not have a high enough flow.
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Unread postAuthor: williamfeldmann » Mon Aug 11, 2008 3:45 pm

trooperrick wrote:How is that valve working? I heard somewhere that they don't open fast enough. I think the person may have just done a crappy job modding it.


Whats more likely is as Maxus mentioned, too small or slow of a release valve. A blow gun is about at small as I would want to put on a 1 inch valve. In fact I have a blow gun that I used on my first one that I don't use anymore because it has less flow than these that I use now. 1/2 ball valves or something similar are probably a better choice. I have heard of people using 3/4 inch or 1 inch sprinklers valves on 2 inch and bigger pistons and sprinklers.
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Unread postAuthor: starman » Mon Aug 11, 2008 5:35 pm

Really nice setup there! I like the tee breech loader and general layout...I can tell lots of thought went into it. I do also like the stock you've built ...alot. I would just worry about the weight build-up of the gun in total.

You could save a little weight by chopping some of that tank down to 1/2 or 2/3 its present size. Cutting it in half would give you roughly a 1:1 c:b ratio and for a barrel that long and golf ball projectile, that is plenty of power. It would save you a bunch of hand pumping as well.

However, the long tank does certainly look good on there... :wink: Great build!
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Unread postAuthor: blind909 » Mon Aug 11, 2008 5:43 pm

It would look even better if you painted all the PVC black, and stained the stock with some wood stain :lol:. But overall its an awsome rifle.
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Unread postAuthor: FishBoy » Mon Aug 11, 2008 7:35 pm

nice build, can you get that electrical sch 80 at home depot?
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Unread postAuthor: jackssmirkingrevenge » Tue Aug 12, 2008 1:11 am

Nice and "complete", love the Harris :D it deserves a desent sight of some description though, and a paint job.
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Unread postAuthor: williamfeldmann » Tue Aug 12, 2008 7:07 am

I did consider shortening the chamber some when building it but I thought the look was off. The stock is two chunks of 2*6 so it is about 3 inches thick. Overall I would guess it weighs close to 75 pounds, so shortening the chamber won't save me much weight.

Like I mentioned, I am going to build a little sister to this one and will be putting a stock on it also. It will being getting a good paint job and staining.

Yes, electrical conduit should be available at almost any home center. Sometimes sch 80 is not on the shelves but it is a common size so ask for it if you don't see it.

Jack, I always value your opinion. I can eyeball aim it to hit one of those 55 gallon trash can lids at around 100 yards or so. It is a smoothbore so a set of "iron sights" would be wasted but what about a ghost ring type sight? You have any thoughts on a not-scope style site?
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Unread postAuthor: starman » Tue Aug 12, 2008 9:15 pm

williamfeldmann wrote:I did consider shortening the chamber some when building it but I thought the look was off. The stock is two chunks of 2*6 so it is about 3 inches thick. Overall I would guess it weighs close to 75 pounds, so shortening the chamber won't save me much weight.


Yoowwie, 75 lbs. As nice as they look, those 2 x 6s are killing you weight wise. I wonder if you could fashion some foam pieces cast with light coat of fiberglass or carbon fiber.
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Unread postAuthor: Solar » Tue Aug 12, 2008 11:16 pm

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Go to a scuba shop and ask for a bouyancy compensator (BC) fill nipple with a 1/4" NPT male thread. Then just use a regular BC fill hose with the pin valved line that shuts off the flow when disconnected.

Throw the gauge over shoulder through harness straps and read "upside down"
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Unread postAuthor: jackssmirkingrevenge » Wed Aug 13, 2008 4:28 am

williamfeldmann wrote:I can eyeball aim it to hit one of those 55 gallon trash can lids at around 100 yards or so. It is a smoothbore so a set of "iron sights" would be wasted but what about a ghost ring type sight? You have any thoughts on a not-scope style site?


The closest analog to a spudgun in terms of smoothbore accuracy as far as firearms are concerned are shotguns so they make a good starting point in terms of inspiration.

Have you considered buying a cheapo red dot sight? It won't break the bank, can be fitted with the simple expedient of epoxying a metal plate of the appropriate width to the barrel. Also being a "scope" it will suit the "sniper" looks brought about by the long barrel, rifle type stock and bipod.
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Unread postAuthor: williamfeldmann » Wed Aug 13, 2008 8:09 pm

I had considered trying to tap into the barrel and mounting one of my spare weaver rails. That way it can come back off. I have an extra 40 mm red/green laying around. I may try it. Do you think I could make a reasonably accurate ghost ring that can mount on a weaver rail just out of aluminum bar stock?

On a side note, how can I add a preview picture to my main post so it shows up in the forum main page?
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Trying to figure out how to make a SCUBA first stage regulator work for portable charging station. If only that pesky job thing didn't keep eating up all my time...

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