I have spent the better part of a decade modding and working on sl68ii's.
the age old question was how do I get the velocity up on it? Ive found the procedure for doing so. Mind you I'm doing this with hand tools and have no special equipment. So you can update the procedure to whatever tooling you have. Here goes.
Step 1. Use a carbide burr bit for a Dremel and file down the hump on the plug on top of the body above the valve chamber so it's flat to accurately center punch on the pin.
Step 2. Use a 3/32 drill bit and go extra slow and drill down the center of the plug. let the weight of the drill take it down or if you go too fast the bit will go off course. You're going to need some good steel drill bits to make it through. Once that's piloted out proceed to step up one size at a time to a 13/64 drill bit. When drilling down into the grip go a little at a time. There's no hurry in connecting the two holes. You can't take it back. I had to braze a hole shut due to rushing. Make sure to keep clearing the shavings. I noticed while drilling this aluminum it plugs up the bits really easy and throws the bits off course.
Step 3. Begin drilling the hole through the grip towards the valve chamber. Start with a 1/8th inch drill bit and move up every step to 13/64, same procedure. Drill a little at a time and clear the shavings. Eventually you'll reach your hole through the top. If you go too far too fast you'll drill right through the grip. I use a curved diamond file to clean up the holes inside the valve chamber so it doesn't cut o-rings
Step 4. Tap the upper valve chamber hole with a 1/4-20 tap and go a little at a time clearing the chips out of the hole. It keeps from chewing up the threads. When tapping the hole stop just before the bottom of the hole. Install a 1/4-20 set screw and use red loctite (the devil's anus) to seal the threads. It never needs to come back out. I've also used a 2 part high psi epoxy.
Step 5. use a pointed carbide burr to port out the holes on the valve stem. Don't go too far or the valve stem will snap from the hammer hitting it. It can be done with the valve cup seals left on being careful. I just tried finding cup seals and they are out of stock everywhere.
Step 6. I use a 1/4 inch lock washer the daimeter of the valve stem and twist it flat so it's not offset. install it on the side the hammer hits to open up the valve more and increase output. The most I've ever needed was one. But you can play around for different results. Also if you have a 3d printer you could make different size shims to increase of decrease airflow.
no shims or anything required behind any of the springs.
I polish up all of the internals with 6000 grit sand paper with oil on it. After cleaning the internals I polish inside of the gun and all of the internals with a hoppes wax polish rag and that really smoothes out all of the little scratches and makes everything real buttery. Those wax rags work wonders on everything inside and out and makes things shine.
Yesterday I modded eight of them and was able to achieve between 300- 345 with multiple shots on every one of them with a normal output tank.
I had a couple that chronoed low and figured out depending on the barrel you have on there the stock front bolt o-ring will be too small and you'll lose 20-30 fps with that o-ring not fitting tight in the barrel. Once i found one that was tight it went up over 300.
i haven't shared this cause at one point in life I wanted to be the guy to do it for people. I'm older and run my own business now and have decided to share this so everyone that likes sl68's can enjoy what me and everyone on my team has had for years. Here you go guys. I hope the instructions are clear enough. If you have any questions ask. I don't quite know how to navigate this site yet and do captions with pictures so bear with me. But I will upload pics as well.
the age old question was how do I get the velocity up on it? Ive found the procedure for doing so. Mind you I'm doing this with hand tools and have no special equipment. So you can update the procedure to whatever tooling you have. Here goes.
Step 1. Use a carbide burr bit for a Dremel and file down the hump on the plug on top of the body above the valve chamber so it's flat to accurately center punch on the pin.
Step 2. Use a 3/32 drill bit and go extra slow and drill down the center of the plug. let the weight of the drill take it down or if you go too fast the bit will go off course. You're going to need some good steel drill bits to make it through. Once that's piloted out proceed to step up one size at a time to a 13/64 drill bit. When drilling down into the grip go a little at a time. There's no hurry in connecting the two holes. You can't take it back. I had to braze a hole shut due to rushing. Make sure to keep clearing the shavings. I noticed while drilling this aluminum it plugs up the bits really easy and throws the bits off course.
Step 3. Begin drilling the hole through the grip towards the valve chamber. Start with a 1/8th inch drill bit and move up every step to 13/64, same procedure. Drill a little at a time and clear the shavings. Eventually you'll reach your hole through the top. If you go too far too fast you'll drill right through the grip. I use a curved diamond file to clean up the holes inside the valve chamber so it doesn't cut o-rings
Step 4. Tap the upper valve chamber hole with a 1/4-20 tap and go a little at a time clearing the chips out of the hole. It keeps from chewing up the threads. When tapping the hole stop just before the bottom of the hole. Install a 1/4-20 set screw and use red loctite (the devil's anus) to seal the threads. It never needs to come back out. I've also used a 2 part high psi epoxy.
Step 5. use a pointed carbide burr to port out the holes on the valve stem. Don't go too far or the valve stem will snap from the hammer hitting it. It can be done with the valve cup seals left on being careful. I just tried finding cup seals and they are out of stock everywhere.
Step 6. I use a 1/4 inch lock washer the daimeter of the valve stem and twist it flat so it's not offset. install it on the side the hammer hits to open up the valve more and increase output. The most I've ever needed was one. But you can play around for different results. Also if you have a 3d printer you could make different size shims to increase of decrease airflow.
no shims or anything required behind any of the springs.
I polish up all of the internals with 6000 grit sand paper with oil on it. After cleaning the internals I polish inside of the gun and all of the internals with a hoppes wax polish rag and that really smoothes out all of the little scratches and makes everything real buttery. Those wax rags work wonders on everything inside and out and makes things shine.
Yesterday I modded eight of them and was able to achieve between 300- 345 with multiple shots on every one of them with a normal output tank.
I had a couple that chronoed low and figured out depending on the barrel you have on there the stock front bolt o-ring will be too small and you'll lose 20-30 fps with that o-ring not fitting tight in the barrel. Once i found one that was tight it went up over 300.
i haven't shared this cause at one point in life I wanted to be the guy to do it for people. I'm older and run my own business now and have decided to share this so everyone that likes sl68's can enjoy what me and everyone on my team has had for years. Here you go guys. I hope the instructions are clear enough. If you have any questions ask. I don't quite know how to navigate this site yet and do captions with pictures so bear with me. But I will upload pics as well.
I have five SLs on the table right now, as soon as I start the machining, I'll take a look at the seals. Material's easy enough, and I could pop 'em out by the bushel in the turning center.
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