Anyone build their air rifles?

I like what this guy did with his old Crosman 760.

Modifications:


Shooting test:


Not sure if I would bother trying to modify a modern Crosman 760. On the upside for the modern 760s, they take the same valve that a 13xx pumper does.

Imo he did some good work on his own to this rifle & he got a nice product for his efforts. From this though you can surmise that spring piston guns are more efficient & simpler machines.
 
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fat tony said:
I like what this guy did with his old Crosman 760.

Modifications:


Shooting test:


Not sure if I would bother trying to modify a modern Crosman 760. On the upside for the modern 760s, they take the same valve that a 13xx pumper does.

Imo he did some good work on his own to this rifle & he got a nice product for his efforts. From this though you can surmise that spring piston guns are more efficient & simpler machines.
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I can tell you moding a 13xx series ain't cheap. You could buy a 500 + FPS for it.

Gun was 89.99

Then my flat top piston was 22$ USD
Flatop valve was 25$ USD
Enlarged transfer port was 18USD
Pin because the stock roll pin sucks was 14$
Seal kits range from 15$
But O rings are 3$ for for the piston.

Longer barrels are around 30$

Then if you want to get into hammer springs, hammer, other work. If your not capable of doing the work. I didnt know so I bought parts to mod mine and then when I saw its hmmm simple turning would do.

You could machine everything your self and would cost less.


One place has a 800 fps for 90$ and another selling a 1200fps for 140$. Canadian.
 
fat tony said:
The only thing I dislike about the 13xx series other than they are pistols is the low profile pump handle. Very uncomfortable while pumping. Otherwise they are a throwback to the early 20th century single shot pneumatics. Great nostalgia.
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Yeah the 2289 pump handle is a improvement ( but $$$, most places want about 30 USD + shipping ) or do what I did and adapt a handle to it. Drill a hole threaded handle from a hammer drill and a nut and washer. Can pump faster w/o pinching my hand in the process..

22711_10153280353686241_3256640277079744267_n.jpg
 
And the 13xx are classed as pistols, so making them over 500fps turns them into restricted firearms. The same goes for the 2289, 2240 and 2250....you need a 2260 tube which is a 'rifle' so you can cross the 500fps threshold.
 
PGW Steve said:
And the 13xx are classed as pistols, so making them over 500fps turns them into restricted firearms. The same goes for the 2289, 2240 and 2250....you need a 2260 tube which is a 'rifle' so you can cross the 500fps threshold.
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Yeah thats the biggest downfall. Other then that the 13XX series is a good source for parts, Everybody makes parts for them. There are 18-24" barrels for them. I never bother to find out if they pass to keep them rifle. so I left it down at a friends in the States.
 
fat tony said:
I guess unless you want to make something from scratch, it is probably a bit more efficient to modify something that is available.
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The top posters in the spudder forums build high power air guns all the time. These aren't your run-of-the-mill plastic pipe potato launchers, we're talking steel barrels, custom lathed aluminum parts, polymer pistons and homemade 2000 psi PCP tanks.

Also Tony, the purpose of the burst disc is to hold onto the initial pressurized air inside the chamber. The way a hybrid works is you "charge" air into your chamber at several times atmospheric pressure, so you can add more fuel to burn into a more compact space, a lot like what happens in the compression cycle on a 4-cycle engine or what the spring in a dieseled airgun does. Since normal valves won't be practical in this sort of system, spudders use a one-use burst disc as the valve. The burst disc is calibrated to break at a certain pressure above the initial charge pressure (its just strong enough to hold the pressurized air inside the chamber), aluminum foil being the cheapest and easiest to make do with, and once the spark is lit, the stoichiometric mixture of compressed air and vapour fuel burns and blows out the burst disc at up to a hundred bars of pressure and sends the projectile in front of the burst disc on its merry way.

I doubt that half the energy is used to break the burst discs in these hybrids, since once the disc breaks, there's nothing holding back the gases but the projectile. Also, the disc helps to hold back the initial combustion event so that the fuel and air inside the chamber has more time to burn completely. Just like how when you seat bullets tighter in a cartridge casing, you get higher pressures since the powder has more time to burn inside the casing.
 
War Song said:
The top posters in the spudder forums build high power air guns all the time. These aren't your run-of-the-mill plastic pipe potato launchers, we're talking steel barrels, custom lathed aluminum parts, polymer pistons and homemade 2000 psi PCP tanks.

Also Tony, the purpose of the burst disc is to hold onto the initial pressurized air inside the chamber. The way a hybrid works is you "charge" air into your chamber at several times atmospheric pressure, so you can add more fuel to burn into a more compact space, a lot like what happens in the compression cycle on a 4-cycle engine or what the spring in a dieseled airgun does. Since normal valves won't be practical in this sort of system, spudders use a one-use burst disc as the valve. The burst disc is calibrated to break at a certain pressure above the initial charge pressure (its just strong enough to hold the pressurized air inside the chamber), aluminum foil being the cheapest and easiest to make do with, and once the spark is lit, the stoichiometric mixture of compressed air and vapour fuel burns and blows out the burst disc at up to a hundred bars of pressure and sends the projectile in front of the burst disc on its merry way.

I doubt that half the energy is used to break the burst discs in these hybrids, since once the disc breaks, there's nothing holding back the gases but the projectile. Also, the disc helps to hold back the initial combustion event so that the fuel and air inside the chamber has more time to burn completely. Just like how when you seat bullets tighter in a cartridge casing, you get higher pressures since the powder has more time to burn inside the casing.
Click to expand...

Thanks for your corrections :). I would like to see more innovation. This forum is the wrong place for this sadly as it is rife with outraged fudds.

An example is when I posted a few vids in the ironically named hobbies & gadgets sub forum. The forum is starting to become a gathering place for trolling fudds. My $.02.
 
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