Tippmann 68 Carbine Velocity Issues

[glaman5266]

I personally like the foregrips. I think the ones with the cut off foregrips look janky with all the squared off metal. Simpler & smaller? Yes. Aesthetically pleasing? Nope.

Can't speak for the .68 Carbine, but I like the feed on my Pro Carb. Doesn't rock around much & if it ever does I can pad it with a little felt like people do with their 98 elbows.

[Myrkul]

I have not yet had a problem with the feed neck on the 68-Carbine, (I also haven't used it) but in my initial digging while waiting for this one to arrive I heard nothing but complaints about the feed neck. Apparently people were super good at knocking them off. I'm honestly not sure how, it seems sturdy and robust and sometimes I need to pry the latch on mine with a screwdriver to get it open, but the stock feed neck was apparently the big complaint back in the day.

[Cunha]

Hey, Cool!

I still can't decide what tippmann to go for. I like the cleaner look of the old 68 carbines vs the pro carbine, but I do like that all pro carbines have cvx valve, and if you chop the shroud off the pro carb can look pretty clean.

Anyone with more experience have their thoughts on the pro carbine feed design vs a metal (or even plastic) 68 carbine feed design? Which one is more solid or functional?

[Myrkul]

How is the front bolt oring? Any drag? If it’s swollen it will cause low FPS, though usually bolt stick as well. I generally take them off as they make no difference.

ps when I drilled out my power tube I got about a 30fps jump so I’m feeling like there is something else going on here

Front bolt "o" ring was replaced with the others, I tried pulling it as per your recommendation, and noticed it liked to catch on the front detent on the return causing some inconsistent recocking. I threw it back on since there was no noticeable velocity improvement with it off and it moved freely and easily anyway and won't chew through my detents this way.


During the disassembly I finally shredded the seal at the top of the adapter fitting, it was fishing line thin and probably original, so I'm not terribly surprised. Figuring I had nothing else to loose at this point I grabbed a spare clippard rubber grommet that looked around the right size, slapped it in the valve, and then drilled out the adapter fitting to increase valve volume. I had to screw it in extra tight to get the rubber grommet and now drilled out adapter fitting to seal, but its the first thing that worked! I "think" I have the velocity issue fixed, at least it looked that way when test firing in the back yard. I'll have to make it to a chrono to tell for sure, (hopefully in the next few days) but it was noticeably hotter and much louder so I'm very optimistic.

[Chappy]

How is the front bolt oring? Any drag? If it’s swollen it will cause low FPS, though usually bolt stick as well. I generally take them off as they make no difference.

ps when I drilled out my power tube I got about a 30fps jump so I’m feeling like there is something else going on here

[Myrkul]

What about a pro carbine CVX valve since all pro carbs have em?

That sounds like it would work to me, does anyone who has both care to chime in?

Another interesting thought, Jordan here is running modified Prolite powertubes in his 68- Carbines, and he said he had trouble getting them to shoot low enough to be field legal. Following his advice is what caused me to drill out the cross section in the powertube for mine, sadly for marginal to no improvement. I wonder if deliberately switching to a Prolite powertube would yield better results? Anyone know where to find one of those? Alternatively, maybe I could wrap the 68 carbine power tube in Teflon tape at the base to create a better seal against the body? Do we think that would help or just have the same impact everything else I've done has?

[Myrkul]

I sadly only have the one carbine.

If anyone wants to send me a second one so I can do this strategy I'm game though!

[Cunha]

What about a pro carbine CVX valve since all pro carbs have em?

[Myrkul]

Everything was torn apart to remove 20 year old nasty ass Teflon tape, and resealed with blue locktite. When I pull the expansion chamber tonight I'll double check for clogged filters, but I don't think anything is there.

[Myrkul]

Didn’t know any of that. Good info. Thank you.

On that thought- how different are these CVX valves from the newer ones? Would a valve swap work?

Unfortunately a valve swap with a newer CVX won't work. I'd have to keep the body the same. It's the valve internals that are interchangeable.

I actually have a spare (albeit beat to death and dirty as sin) 68-Carbine valve I&I recently sent me by mistake. Took me a while to figure out what it was till I matched them, but I luckily didn't even have to tear anything apart for these pictures. You can see how much smaller the Carbine valve is, I think this decreased volume is what is primarily responsible for the low velocity, and since I can't think of an easy way to add valve chamber volume because of that adapter fitting, I'm thinking the SHP Reg is looking like a better and better option.

Right: Tippmann 98 CVX valve (1/8" NPT version)
Left: 68-Carbine CVX valve

[BrickHaus]

You look for a brass filter in every fitting? Could still have one hidden thats clogged up.

[Cunha]

Dang now I can't decide if I should just use a tippmann 98 as my tippy of choice. Sorry I can't be of help. the only thing I can think of is to swap everything from a different gun that confirmed works, or part by part swap till you find what works (like a real science guy)

[glaman5266]

Didn’t know any of that. Good info. Thank you.

On that thought- how different are these CVX valves from the newer ones? Would a valve swap work?

[Myrkul]

Just a shot in the dark here- maybe try running the bottomline straight to the valve w/no x-chamber? If that doesn't work, maybe a siphon bottle? Not sure how durable the valves are in the 68 Carbines are though... And I thought the CVX valve didn't come out 'til the Pro Carbine. Hmm.

The CVX valve came out early into the production of the 68 Carbine, eventually they came stock and for a time older ones could be sent to Tippmann and converted to CVX. I called Tippmann and they confirmed that this one had the CVX valve because of the specialty brass fitting (pictured below) that screws into the body and has a crazy tiny "o" ring on the top that is pinched against the CVX valve body to create a seal. I suspect this fitting is a choke point for the valve, since the air passage is TINY, but Tippmann also made it pretty clear to me that the specific fitting was the reason they would no longer be able to do any "more" conversions, because they were out of the fitting and would never be able to get more, so I'm reluctant to drill it out and see if the extra volume helps (I am sure it would). I'm not overly concerned with the durability of the valve at higher pressures, it takes all standard CVX parts except the valve body itself and the external "o" ring.

I've built and used siphon tanks before for a Sheridan P-68 that was doing the exact same thing, it did "work" but co2 fills at my local field are hit or miss and the continual pain in the ass of finding someone who could correctly fill a siphon tank made sure the gun and tank didn't stay in my collection for more then a few months. So the SHP is definitely a more attractive solution to me then a siphon tank.

I'll try pulling the expansion chamber later today and report back.

Specialty CVX adapter fitting:

[glaman5266]

Just a shot in the dark here- maybe try running the bottomline straight to the valve w/no x-chamber? If that doesn't work, maybe a siphon bottle? Not sure how durable the valves are in the 68 Carbines are though... And I thought the CVX valve didn't come out 'til the Pro Carbine. Hmm.