Paintball

[nemian lion]

Hi everyone.

I recently restored a rusty POS Sheridan P68 SC and I am wondering what kind of work I can do to get better efficiency? I get about 20 or so good shots on one 12 gram at around 255FPS (was still cold outside). I already have a RVA and thinner piercing stem from Palmers. Are there some easy mods I can do to improve its efficiency? Replace the speed demon bolt velocity adjuster with a screw and teflon tape? What about a new bolt altogether? What are your recommendations?

[chplnstone]

one way is to increase to size of the transfer hole between the valve tube and the barrel. not easily done, usually have to send it out to palmers unless you're handy with either a drill and tap or torch...is it a cartridge-valve type? another method is 'turbo valve'-ing it, which is just boring out the holes in the valve itself, or in the case of a cartridge valve, the transfer hole out the top...i doubt the bolt will affect it much, but the condition of the barrel will (a little) by causing drag if not polished and having a good paint/barrel match...

[nemian lion]

i have the non-cartridge valve, what about increasing the four holes in this piece? (cant remember the name) Is that what you are talking about?


I think my barrel is pretty good, I removed the over-sprayed paint and brasso-ed the crap out of it.

I guess I am asking what I can do short of sending it away to Palmers? Is my velocity and shots per 12 gram ok (~255 and 20 shots per 12 gram) or can it be better?

Also I sheared the rod locking pin in the bolt knob but luckily it is long enough so I can still grab it with pliers to remove the cocking rod. Will a PGP bolt knob fit or some other stock part fit or will I have to pay Home Depot a visit?

[chplnstone]

yup, that's the one...boring out the holes will help a little, i usually use a #3 bit...that, cleaning, and maybe using a palmer's dyna cupseal are about all i know of that you can do before either sending it off or opening up the transfer hole yourself...i know of 2 ways to accomplish it, either drill up through the bottom of the valve tube into it, then tap and plug the exterior hole, or sweat the tubes apart, drill it out, then re-solder...

the pump rod release pin is a fairly common problem, i could use a couple myself, try here: Products or good luck at a good hardware store...i just haven't found the time to look myself

[nemian lion]

what is the size and threads for the speed demon velocity adjuster? I think i will replace it with a solid screw instead of the machine grooved screw and bearing combo. My velocity adjuster screw fit a 8mm X 12mm test nut but the same type screw doesnt fit my bolt.

[nemian lion]

anyone?

it isn't a 8mm X 12mm. what is it?

[Surestick]

Originally Posted by nemian lion

i have the non-cartridge valve, what about increasing the four holes in this piece? (cant remember the name) Is that what you are talking about?


I think my barrel is pretty good, I removed the over-sprayed paint and brasso-ed the crap out of it.

I guess I am asking what I can do short of sending it away to Palmers? Is my velocity and shots per 12 gram ok (~255 and 20 shots per 12 gram) or can it be better?

Also I sheared the rod locking pin in the bolt knob but luckily it is long enough so I can still grab it with pliers to remove the cocking rod. Will a PGP bolt knob fit or some other stock part fit or will I have to pay Home Depot a visit?

What Palmer's does is bore out the top hole only, block the side holes and fill the bottom hole with a set-screw to keep the top hole aligned.
energy from the air coming out the side holes is going to be lost to turbulence, etc.
When you think about it getting the max efficiency really means getting the air you need to fire the ball to the ball as fast as possible. The longer you take to get the air to the ball the more the ball will have moved down the barrel and the more volume behind the ball you will have to fill to get the pressure you need to get the ball up to speed (that's over-simplifying things a bit but you get the idea).

I've seen ~ 40+ shots per 12gr from my Palmer's tuned PGP at 260ish FPS. 20 sounds more like a stock P68, you can definitely get more.

[c6quad]

Originally Posted by Surestick

What Palmer's does is bore out the top hole only, block the side holes and fill the bottom hole with a set-screw to keep the top hole aligned.
.

the top hole isn't the only thing they bore. the inside bore of the exhaust valve body itself is bored to .266".

[nemian lion]

Originally Posted by Surestick

What Palmer's does is bore out the top hole only, block the side holes and fill the bottom hole with a set-screw to keep the top hole aligned.
energy from the air coming out the side holes is going to be lost to turbulence, etc.

makes sense to me... instantaneous pressure behind the ball will be most efficient. how would you align the valve so the bored out hole is facing up though?

[russc]

You have to make a hole in the bottom like on an autococker.