Working on a new airgun

[theairgunman]

I'm currently working on a new airgun, one that I plan on using for deer hunting in MO for the '09 season. It is a shoulder fired coaxial, 44" overall length. According to GGDT, it should reach velocities of 425 fps, producing 130 fpe at the muzzle. This is using massive .600 lead balls, weighing ~324 grains. Using a ballistic calculator, by sighting it in at 50 yards, trajectory will rise to 6.33" at 25 yards. Combining a range finder and ballistics table, it should prove quite lethal out to 50 yards (108 fpe at that range). I recently watched a video of a buck being downed by a smaller caliber (.45) airgun at 25 yards. This airgun put out more power, and almost penetrated out the opposite side. I've calculated a taylor KO factor of it being 7.00 and a thornily stopping power of 30. My airgun would have a KO factor of 12.50 and a thornily stopping power of 46. The thing I'm most worried about is penetration of the larger bullet, which is key when hunting with airguns. One calculator I found shows the .600 having a better penetration index, but my experiences hunting with a .177 vs a .22 makes me skeptical. Do you all have any thoughts on the ability of this airgun to take down a deer?

[theairgunman]

Got the airgun in working order, it fires fine at 70+ psi. It held air for 1.5 hours with no leaking, so I think it is time to add a trigger system and make it practical for shooting. No chrony numbers yet, hopefully soon.

[theairgunman]

I was able to take some test shots in my garage this afternoon. The results were impressive, even at a "low" pressure of 100 psi. For my first shot I used a 1/2" marble that weighs around 40 grains. Shooting from the 15 feet my garage affords me, the marble passed 3/4 of the way through my backstop. The backstop is a heavy cardboard milk box stuffed with layers of plastic sheeting. Next, I placed a sheet of 5/8" particle board in front of the backstop and loaded a 278 grain .58 caliber muzzleloading ball. It punched right through the particle board and went half way through the backstop. It squished about half way, you could even see the fabric imprint from the wad! Here is a picture of it:

Next, I tried a marble on another sheet of particle board. It too went through the board, but stopped once it got just inside the backstop. These tests show a lot of hunting potential, I'm looking forward to chronographing it soon, weather permitting. In the mean time, I've got a trigger and sighting system to work on... 

[Pellethuntr]

 I don't think you'll be able to kill a deer very humanly with that.

[theairgunman]

Yeah, it would have to be a close up well placed shot to bring one down nicely. After I complete this one, I'm going to build a high pressure one out of copper or seamless stainless steel pipe. Deer season here tends to be colder than PVC is to be used at 

[Pellethuntr]

 I wouldn't use PVC for anything! Go with steel and iron. I don't know if u have seen this but jerks sporting goods has a paintball tank that runs on air instead of co2 and is reged down to co2 level. That would work for the cold weather but It's about $100! It's a little out of my budget right now.

[Pellethuntr]

 Question are U going to cast those massive bullets your self? Because I don't think there is any manufacturer who makes a RB that big!

[theairgunman]

Yeah, I'll use a Lee RB mold for it. I might even make my own mold for a foster slug, I've done that before with pretty good success. The main thing is making sure the inside cavity is perfectly centered.

[Pellethuntr]

 Got ya sound like it will be potent medicine for just about any critter just not a deer yet. Make a new one out of steel and iron, fill it with co2 or something of that pressure and then you'd be brewing a real weapon!

[theairgunman]

Yeah, the final version will be made from copper and probably be filled off of a shock pump or homemade multistage stirrup pump. I'm looking at a pressure between 300 and 850 psi. CO2 would be great except for when the cold weather hits. I'd like to get a barrel liner from track of the wolf so I could enjoy the greater accuracy and ammo choice that a rifled barrel would afford me. The cost of the barrel alone would be several times the cost of the rest of the gun, so I'm not sure I want to take that route We'll see how much overtime I get before I make my final decision. lol

[Pellethuntr]

 I used an old muzzleoader barrel for mine.