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Unread postAuthor: jackssmirkingrevenge » Mon Apr 20, 2009 3:15 pm

ALIHISGREAT wrote:Gippeto... that muzzle is amazing!


Agreed!

psycix wrote:-BFWB for 6mm BB's
-BFWB for marbles
-Some other funky fullauto system in combination with a BFWB or else replacing it


I was thinking, since this valve clearly has power to spare, maybe it's worth revisiting the cartridge fed breech... Low shot count isn't a huge worry, there's only so many cartridges I can make :roll:
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Unread postAuthor: sputnick » Mon Apr 20, 2009 3:27 pm

Gippeto, I love the crosman backpacker, a shame it is discontinued, Me being a poor-as-heck teenager, and being in supreme debt I have to hope that the local store doesn't sell out until I save up the money.

Do you know of any other .22 multi-pump gun that could act as replacement if they do run out?

And as everyone knows, my project is a marshmallow gun, just like a tiny HEAL, but the damned piston will not work, probably because it's so small it's hard to get a nice piston, If it just lies flat against the piston, it doesn't seal. If I put it in front of a foam backing, the rubber explodes out the barrel. I will put more work into it once I decide on the approach I will take.

Now, some pictures to tide you over :wink: :D
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Unread postAuthor: THUNDERLORD » Mon Apr 20, 2009 4:57 pm

I mentioned it in a few other replies but I figured it's time to build a version of JSR's blow forward bolt and the rest to go with it.

I was looking at brass fittings for a high pressure burst disc design but also thinking of unregged co2 since dry ice is available nearby.
So I started designing a BFB instead.

My design is different (than link above) because I cut two or four grooves into the back of the BFB casing and add a "+" or just "-" and attach the blocker pin "-" to the center.
That way the pressure flows into the entire BFB (constricted only by the narrow side of "+" and blocker pin).
Hopefully it will use a homemade piston valve, (although a qev threaded onto the BFB would probably be more simple).

Today I checked into it (again) and looks like A 3/4" brass "T" ,3/4" close nipple, and 3/4-1/2" reducer coupling will contain the 1/2" brass nipple BFB casing that will thread from the inside of the "T" into the inside of the reducer coupling. (sleek design)
That way the piston seat and piston can be larger.
Also a 1/2-3/8" reducer bushing threaded into the coupling for barrel mount and front of BFB.

Still haven't plugged into D_Hall's GGDT to check reasonable volume for the hopeful pressure range.
Some parts will require drilling slightly too.
I plan to grind some of the threads (slightly) to get everything flush and keep the threads non-exposed. Also to polish and darken the brass eventually.

I like this project because it fits in a small box and my new place is small.
BTW I forgot it to mention it will be 3/8"(.375) bore and hopefully use conical or round shot. And maybe have a .25 barrel also.
Pain I'm working between two places now. Gotta go for today :( :) 8)
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Unread postAuthor: Technician1002 » Mon Apr 20, 2009 6:24 pm

sputnick wrote:
but the damned piston will not work, probably because it's so small it's hard to get a nice piston, If it just lies flat against the piston, it doesn't seal.


In one of my home built QEV cannons, I had the same problem. Even if the barrel is perfectly flat, sometimes the T isn't perfectly straight so the piston hits the seat at an angle. My solution was a dowel with stick on sandpaper on the end that could fit the same diameter as the piston. With the dowel aligned in the valve cylinder, it is rotated to sand the valve seat perfectly true to the valve cylinder. To tell when you are finished, I paint the valve seat with sharpies. When the painting wears off evenly all the way around, you are done.

Attached is a photo of the breech of a tennis ball cannon with a 2.5 inch barrel that I built. The piston o ring is in the cylinder wall to keep piston mass down. Note the black marks on the valve seat. They are now evenly worn down from sanding the seat true.
The o ring in the valve seat is to reduce the piston mass. The groove is filled with caulk and the o ring is squished into place. A greased piston holds it in place while the caulk sets for a true seat.


Cannon spec TB cannon.
6 inch chamber coaxial 28 inches long
2.5 inch barrel 8 feet long.
3 inch piston.
Valve seat o ring diameter 2.75 inch
pilot valve 1/4 inch ball valve (this is a quick exhaust main piston)
Weight, too much!

For size comparison, that is a full size spray paint can in the barrel.
:D
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Breech of 2.5 inch QEV tennis ball cannon.
Last edited by Technician1002 on Sat Sep 26, 2009 11:11 am, edited 2 times in total.
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Unread postAuthor: Moonbogg » Mon Apr 20, 2009 7:19 pm

YES! Thw back packer pelet pistol kit FTW!! I used to love that thing. Nice cannon. Impressive muzzle!
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Unread postAuthor: mark.f » Mon Apr 20, 2009 9:20 pm

sputnick wrote:Gippeto, I love the crosman backpacker, a shame it is discontinued, Me being a poor-as-heck teenager, and being in supreme debt I have to hope that the local store doesn't sell out until I save up the money.


For mine, I didn't get a backpacker, but I got a multi-pump 1377 air pistol, which I then added a longer barrel to and a stock, along with a steel breech and bolt.

You could get a 1322 pistol and do something similar.
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Unread postAuthor: sputnick » Mon Apr 20, 2009 9:39 pm

Well quite frankly mark, I am not really set on the crosman, All that I really want is a .22 (for, dare I say hunting?) and an air powered one, like multi-pump so that I can silence it, so I can make late night shots in and out of the house. My spring gun, always produces a loud twang, which in the dead of night can be heard blocks away.

that, and I really want a real silencing challenge, so I can work on building one that looks pro, and that really works.

I am looking to go all the way, and save up for a benjamin Discovery, since they can go a long time without recharging, are very powerful, and are cheap :) not ideal for silencing with the air tank there, but that could be my cross to bear :wink: gunna have to wait till I go get my gun license, since us Canadians cannot own a gun over 500 fps without one.
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Unread postAuthor: jook13 » Mon Apr 20, 2009 9:57 pm

I would love to own that benjamin. I have had the pump action .22 since I was around 10 and it still treats me right. The PCP above looks sweet.
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Unread postAuthor: sputnick » Mon Apr 20, 2009 10:02 pm

@jook, yeah it looks like a fantastic gun, only charges to 2000 psi, so easy to fill with a pump, you get around 50 good shots with one fill, available in .22 and .177, dead accurate, only about 5 pounds, and up to 900 fps (.22)

and best part, only about 300$ (400$ if you're buying it with the pump, I certainly would)


I hope to get my license soon :twisted: :D :wink:
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Unread postAuthor: jook13 » Mon Apr 20, 2009 10:04 pm

It is also compatable with co2, a cool perk for those that dont like to pump.
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Unread postAuthor: inonickname » Mon Apr 20, 2009 11:04 pm

Well my mini hybrid tester was a fail...

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Leaks from the burst disk coupler..
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Unread postAuthor: Gippeto » Tue Apr 21, 2009 12:10 am

Yes Mark, I've got the bug (again) and you're to blame. :D

It's an air stripper, modeled on one used by Steyr.

The Crosman Back packer is still available from mail order sources in Canada.

D&L, or Scopes&Ammo to name two easy ones. I think LeBaron and SIR Cabellas have them as well.

I bought that one at Canadian Tire on clearance for $62.50 and they gave me a $10 gift card and CT money to boot. :D

JSB Predators group really well in this one... now. :twisted:
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Unread postAuthor: jackssmirkingrevenge » Tue Apr 21, 2009 12:13 am

sputnick wrote:not ideal for silencing with the air tank there, but that could be my cross to bear[/img]


You could get creative, either removing the existing muzzle fitting and replacing it with a silencer attachment, or sleeving the entire barrel/chamber from the 8-clamp forward in a larger tube. Still, I'm guessing it's not really that loud to begin with.
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Unread postAuthor: sputnick » Tue Apr 21, 2009 3:18 pm

Gippeto wrote:
The Crosman Back packer is still available from mail order sources in Canada.

D&L, or Scopes&Ammo to name two easy ones. I think LeBaron and SIR Cabellas have them as well.

I bought that one at Canadian Tire on clearance for $62.50


Gippeto, I did not know you were from Canada! Thanks for the tip, I entirely forgot to search SIR, and now I know even more Canadian gun stores, thanks a million! :D

@JSR, I realize now, that that sounded like I was saying it was a bad thing having that obstacle to overcome, But anywho, it is irrelevant now that I can get the backpacker,

My supreme goal was to make the silencer out of an Arizona can, and the internals of paper/card type materials, so it can be easily destroyed or disposed of whenever without wasting a great deal of money should I need to build another, or dispose of the existing one for whatever reason.
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Unread postAuthor: jackssmirkingrevenge » Tue Apr 21, 2009 11:53 pm

sputnick wrote:My supreme goal was to make the silencer out of an Arizona can, and the internals of paper/card type materials, so it can be easily destroyed or disposed of whenever without wasting a great deal of money should I need to build another, or dispose of the existing one for whatever reason.


I like how you think :)
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