SpudFiles

You would think that one could find this sort of info in a simple search, but I have been unable to find anything that has been helpful...

Here is my one inch piston valve, built into a simple over-under.



The chamber is 21" of 2" sch40 PVC.

The barrel is 2 feet of 1/2" sch40 PVC.

Breech load, via the ball valve with a hole in it's side.


Now...

Using one square of toidy paper as wadding/sabot, I load it with a single steel hunting shot. (3/8")

Loaded by wrapping the shot in the paper, then stuffing it into the ball valve, paper first. Packed in pretty solid, using a wooden stick. So the paper not only carries the shot, but ends up being pretty tightly packed behind it as well.

I am using air pressures just over 100 pounds. (My current guage on the filler only goes to 100, and is more than topped out. I'll have a secondary guage prepared soon, that will measure the actual pressures I am getting.)

I don't think it can be over 120 to 125 pounds.


At ~35 feet, I am getting half penetration in a 3/4" piece of old, very solid, and also soaked through and through... Piece of plywood.

I would like to get that pellet all the way through, at that distance.

Any suggestions on how to increase the power ?

I can go to a 4 inch by 2 foot chamber. But I haven't seen anything that would indicate that that would make much difference. Since I am already at a chamber volume much higher than barrel volume.

Looks nice really likes the ball valve reload system

Any suggestions on how to increase the power ?

Slightly larger barrel with a sabot. Force = Pressure times Area.
You can only slightly increase the area due to the flow limitation of your valve. Try a 1.25 inch barrel. Worked for me for launching D cell batteries from my Marshmallow Cannon.

1 inch valve, 1.25 inch barrel.

Or go full metal and increase the pressure MOAR pressure is good

I agree with Tech... A larger barrel diameter will do wonders. For an example compare SB15's old hybrid with a 3/4" copper barrel to what I believe is a 1.5" barrel now, the damage and muzzle energy is greatly increased. you can see this dramatically in GGDT or HGDT as well

I do know with a larger valve, chamber, and barrel, a sabot does wonders in smashing AA batteries. The increase in power even at lower pressure is impressive.

Technician1002 wrote:I do know with a larger valve, chamber, and barrel, a sabot does wonders in smashing AA batteries. The increase in power even at lower pressure is impressive.

With a larger valve, chamber and barrel......

It's a whole different airgun !

I was hoping for a mod of some sort, or something like that, to make more penetrating power with what I already have.

It's probably not a searchable topic, because it is probably not all that do-able, without major changes.

I have the materials to try a 3/4", a 1", and maybe a 1-1/4" barrels. I'll go that route and see what happens.

Thanks all !

I'm surprised you can pilot with a blow gun, pilot volume seems to be on the larger side. Any chance we can get a piston picture?

EDIT:
As far as increasing power goes, most of the time, a larger pilot valve can help opening speed. I don't know how long your barrel is, but I'd go for 1:2 C:B ratio at this pressure

Lockednloaded wrote:I'm surprised you can pilot with a blow gun, pilot volume seems to be on the larger side. Any chance we can get a piston picture?

EDIT:
As far as increasing power goes, most of the time, a larger pilot valve can help opening speed. I don't know how long your barrel is, but I'd go for 1:2 C:B ratio at this pressure

No problem...

Here are the parts.



Here is how they are to be put together.



The piston started into it's bore.



Piston open.



Piston closed.



The piston opens instantly. Using just the blowgun.

The pilot chamber volume is smaller than it looks like. The piston is solid, yet light. A wood dowel epoxied into a 3/4" pipe. The pipe was then turned on a drill press, until it was a tight fit in the 1" pipe. And there are a couple of rubber washers working as a bumper behind it.

But I am willing to consider a larger pilot valve. I'll install the 1" sprinkler valve as a pilot for the piston, and see if that makes any difference.

Throwing my .02 on the table....

You've chamber a plenty...a longer barrel may be in order. 36" at least.

Gippeto wrote:Throwing my .02 on the table....

You've chamber a plenty...a longer barrel may be in order. 36" at least.

Now that is something that I should have thought of, myself.

Probably would have, if I hadn't been so intent on trying to keep it small.

That is what I will try first.

Thank you.

Maybe I should also try to find something to use for a barrel, that has an ID, close to the actual OD of the steel shot.

Selador wrote: Maybe I should also try to find something to use for a barrel, that has an ID, close to the actual OD of the steel shot.

That'll help too. Tighter is better where bore/ammo fit is concerned.




Leave it alone Jack.

Gippeto wrote: That'll help too. Tighter is better where bore/ammo fit is concerned.


Leave it alone Jack.

That was my thinking.

The toidy paper makes good wadding, but I am wondering if some/most of it is being blasted past the steel shot, even while in the barrel.

Hmmm. Maybe a piece of wooden dowel behind the shot. The dowel wrapped in tape until it is a very snug fit in the barrel.

Ok, THAT may be something I can try tonight.

~~~~~~~

In fact... I just did !

Wrapped a piece of dowel with first duct tape for body, and then scotch tape for smooth. Until it was a snug fit.

Muzzle loaded that first. Then wrapped a steel shot in TP, just enough to keep it snug in the barrel. Muzzle loaded that next.


This shot was at about 80 pounds. (I wasn't willing to wait for the compressor to fill up again.)


The steel shot made it a bit further into the plywood, and left the hole packed with toidy paper.

What is funny is that the wooden dowel also made contact and made as deep a hole as the previous steel shots had been making.


I think maybe this is proof that a barrel that is the same ID as the steel shot OD, should make a difference.


Tomorrow, I'll try again with a snug wooden sabot like tonight, and use a longer barrel, as well.

make a better sabot

It works

Trust me.

Here is a sabot I used to launch a AA battery. the sabot is the bottom of a water bottle with a swim pool noodle insert. This gave the AA battery a good seal in a 2.7 inch barrel. When used with a 2 inch piston valve, the battery was completely destroyed.

This was much more effective than using the battery in a 1/2 inch barrel.



The remains of the top of the battery are completely flattened.