.50 caliber or .60 caliber

[HunterT]

Okay, here's the scoop. I'm building a single shot air rifle. I want it to have a big bore, and therein lies the problem. I don't know what caliber to make it. Should it be a .60 cal or a .50 cal? What do you like better?

[jackssmirkingrevenge]

It depends what you want to achieve.

In terms of power, for the same pressure in the barrel, the 0.60 cal theoretically has 144% of the power available to the 0.50 cal, but to achieve this you will need a proportionally larger valve and chamber, so more gas consumption, weight, recoil etc.

Availability of ammunition in your chosen calibre is also a factor, especially if you want to go the whole hog and aquire a commercial rifled barrel and use commercial slugs.

[velocity3x]

Hey....welcome Hunter,

Personally, I'd build the 60 cal for more power.

[Ranger]

I would go with 50 cal.

[boyntonstu]

I would go with 50 cal.

75+ caliber using 3/4" copper type L tubing at 600 psi is what I use.

[HunterT]

In terms of power, for the same pressure in the barrel, the 0.60 cal theoretically has 144% of the power available to the 0.50 cal, but to achieve this...

I like that!(144% more power) Nearly twice as much power!

...you will need a proportionally larger valve and chamber, so more gas consumption, weight, recoil etc.

Not too much of a problem there. Gas consumption is not a problem, I use a bike pump. Weight, well I'm not really bringing it anywhere. The recoil doesn't bother me(I shoot 12 gauge) and I'll probably mount it.

Availability of ammunition in your chosen calibre is also a factor, especially if you want to go the whole hog and aquire a commercial rifled barrel and use commercial slugs.

The ammo I make myself. Right now I'm gonna stick to a smooth bore. This is just a plinker cannon.

[Zeus]

So what will you build it from, with a bike pump I guess you won't go
above 100 psi, so if you stay below 100psi you can use PVC.

What type of valve do you intend to use, ball valves work but they
aren't ideal, sprinkler valves are bulky with resonable performance,
piston valves can be hard to build, but they perform very well.

So, any basic design yet?

[HunterT]

I'm using a ball valve. This is my second air gun. I'm still learning. I'm building it out of sch 80 PVC.

Basic design is pretty simple. Chamber, ball valve, barrel. I'll post a pic when I finish.

[jackssmirkingrevenge]

Basic design is pretty simple. Chamber, ball valve, barrel. I'll post a pic when I finish.

Unless you plan on spring loading the ball valve, I would highly recommend that you go for a sprinkler valve. Cheap, easy to mod, much better and consistent performance and easier to aim, you'll know the difference

[HunterT]

I don't know much about sprinkler valves. Any suggestions of valves that work have worked well for you?

[jackssmirkingrevenge]

Everything you need to know here.

[nibbler125]

go 50 cal you can get 50 cal paintballs to fire out of it

[Ranger]

I think you should build a QDV or burst disc @ 50 caliber ( its easy to find 1/2" steel rod to make ammo) .

The QDV is more complicated and harder to make but the end result it give you very high flow and can be a breech loader.

A burst disc is very simple, and effective. Probably the fastest opening "valve" there is. Reload time suffers since you have to change the disc every time.

I'm still learing too but ball valves are simple, I have built 6 ball valve guns and none of them perform very well. I have built 2 burst discs, and they are OK. My QDV is king tho... QDV @ 20 psi can shoot a projectile farther than my ballvalve gun @ 120 psi.

Do some research, find something a little more complicated than a ball valve, but not something that would be too hard for your your second project.

[jor2daje]

I wouldnt recomend a qdv for a starting gun because such good seals and more accurate measuring are needed, I would either go with a sprinkler valve or a homemade piston valve. After I modded my first sprinkler valve the whole concept of differential of pressure became much more obvious and so I was able to easily make my own piston valve.

Do a little reading here then head down to the hardware store, take some stuff apart and start learning

[Hotwired]

I don't follow the dislike of ball valves in here, spring loaded or not.

Accuracy, power, flow are the usual reasons trotted out.

So...

Who primarily uses their cannons for long distance accuracy shooting at steel plate.

And then who uses their cannons for casual plinking at any old rubbish at distances where you don't need a scope to see impacts and it's close enough to find the projectile afterwards.

I've had good experiences with small ball valve launchers - compression fitting types for copper pipe. If I find enough olives, pipe and fittings around I could knock up my favourite layout later today.