Valve work on P68SC

[Raven911]

Ok I have a recently rebuilt P68SC. It only gets 15 usable shots from a 12 gram. The Palmer stock gun I have years ago got double that and is a similar design. Has anyone modded their valves in these older sheridans to be more efficient?

[BrickHaus]

Your over bored barrel is likely the biggest issue. Swell some paint up and see how efficient she is just for grins.

But the initial thing can think of is, re spriging with a stiffer valve spring to achieve less dwell, AND pierce the 12ie less. (Ideally you barely want to poke that hole to get a trickle effect off of your 12ie. Another idea for the pierce is carefully sharpen/ shorten the pierce pin. You also want to reduce dump chamber volume. You can tap the valve and plug one of the exhaust holes to help with this.

[Jordan]

First question is - what 12grams are you using? Crosman chronically underfills their 12 grams - I've seen them vary by as much as 3 grams, with lows of under 10 grams and highs of 13.

Second - velocity? 260fps will net you more shots than 280fps, without a noticeable loss of distance (you're using a SC gun, why are you longballing anyways? 🙂).

Third - as BrickHaus mentioned, paint to bore match is important.

Fourth - enlarging the transfer port between the valve chamber and barrel will help, as will some light valve work, but that makes some people nervous to do on their own.

[Raven911]

Hard to paint bore match the barrel when all of the paint currently made is small as hell. I just rebuilt it with a palmers kit which has their valve stem and pierce pin. So I should try plugging one of the hole in the side of the valve? Sounds easy enough. Any idea where to get a stronger valve spring?

[BrickHaus]

Show us a pierced 12ie. I've seen pps pins be 1/8" too long before. Over piercing will hurt efficiency.

[JeeperCreeper]

Easy to bore match paint with a Freak mod...

[capitalpaintball]

After doing all kinds of mods to my p68sc, I only get 10 shots. Literally vents on 10. I molded the valve, added rear velocity adjuster, put a vert asa for the 12grams. Makes no sense cuz my pgp gets 25.

[JeeperCreeper]

Check your valve stem, could be bent. I had this problem with one of my builds. The stem where the hammer hits was dragging and not letting the valve close fast enough.

[JeeperCreeper]

The valve mod is a good place to start. Theres 4 holes in the valve body. You want to plug the 2 side holes, then drill the lower tube on body to where you can use a set screw to plug the bottom valve hole, and to line up the remaining hole on top with the transfer port. That should bump up your FPS, so then you can back the hammer spring tension off to get back to velocity. Should put you close to 20 good shots per 12 gram. After that, check your pierce, if its too big of a hole, refer to BrickHaus post above.

I also try to stay around 260 fps to pick up more shots.

[capitalpaintball]

my 68SC has the cart valve.

[chplnstone]

for cartridge valves i typically just open up the transfer hole a bit & smooth out the area between the cupseal seat & transfer hole for better hydrodynamic flow. I've also opened up the cupseal seat hole a bit before

[Chuck E Ducky]

I just send mine to ☝🏻 that guy above ☝🏻 and he makes magic happen with all my brass bits. I highly recommend his freak boring service you can even have it XL freak bored.

[JeeperCreeper]

Thanks Chuck 😁

[AnarchicArctic]

Sheridan efficiency is a mad science. Lots of variables at play. Small paint and no wedgits causes havoc at the chrono, usually burying your rva in pursuit of field speeds. Plugging the valve as mentioned will increase your base fps, letting you back off the rva. But, this also makes valve positioning a PIA on reassembly. It’s crucial you get that opening to the transfer hole or you’ll bury that rva even further wondering why your shots are pitiful. Too much main spring strength causes the hammer to bounce on the pin, hurting efficiency and creating a kind of burp sound to clue you in that it’s happening. Too soft of a valve spring will add to this problem. Palmers valve stems in my experience are all over the place length wise. I’ve had to respring many of my valves with dyna stems just to get them pushing far enough to pierce. To this end, I’ve had good luck with Spyder valve springs in a Sheridan valve. Put the skinny end on the stem and the fat end at the base. Play around till you find the one that works for you. This is the mad science. What works for one, doesn’t work in others. I’ve tried straight spring swaps before with different results. Ideally you get a pierce that is larger than a pin prick, but smaller than the diameter of the pin itself. The right balance will add to your shot count. If you want to get really crazy you can lighten your hammer…

[JeeperCreeper]

You want your pin hole more like the top one, the bottom is way too much

[Raven911]

So how do I go about getting the smaller hole? I’m off tomorrow and I’ll pop a 12 gram for you and show you the picture. Anyone remember what size tap I need to use on the valve to cap the holes? Thanks for the help and sorry for the late replies. Been busy

[Raven911]

Wish there was an option for the valve seal that Pierces the 12 gram without even using the balance stem like on the phantom 12 gram changers. Anyone ever swap one out?

[Jordan]

Wish there was an option for the valve seal that Pierces the 12 gram without even using the balance stem like on the phantom 12 gram changers. Anyone ever swap one out?

You're looking for an Instapierce setup, which exist but require a Fastchanger as well in order to seal up the 12 gram fast enough as it pierces.

I never liked the one I had, to be honest... you're better off running some sort of vertical ASA with a Phantom bucket changer.

[Raven911]

Man I would love to run a bucket changed like I had on my super stocker. Here is the 12 gram after I fired 15 rds through it.

[BrickHaus]

That honestly liiks like a good hole efficiency wise.

Personally I think a bucket changer would make life easier, but the added volume is going to further hurt efficiency.

It does like of look like the pin isn't sharp enough as your hole is more smashed than poked. Maybe chuck the valve stem in a drill and carefully sharpen the point?

I'm sure a much smarter person will have better input.

[capitalpaintball]

Put a Vert hanger on mine for a bucket changer. love the way it feels, but as i posted earlier it gets 10 shot shots to a 12gram, so 3oz tank it is.

[Spider!]

I was wondering if you had tried to add a restriction to that vasa. That can help with gulping. I have used set screws with a tiny groove into the threaded port of the vasa or the bucket changer. That or a flat piece of steel with a pinhole between the changer and the vasa. A bottle cap with elastomer liner works for that.

[JeeperCreeper]

I wouldn't mind taking a look at it next time we are at the same event. My little PG8 I made to run on 8 grams gets more than 10 shots with a 5" barrel, so something isn't right

[Raven911]

Looks great but where do you even find one of those vert asa these days? God I miss Cooper T.