Tippmann 68 Carbine Velocity Issues

[Myrkul]

I kept the expansion chamber since it didn't seem to effect things. I used both HPA & Co2. HPA was about 15-20 FPS faster so I used that to play.

When I REALLY hammered the trigger one round the hammer failed to catch once, but that's probably the heavy as hell drive spring I have in it.

I managed to find a blue aluminum front bolt on ebay. I figured since it's a known wear point I might as well replace it with something more durable. If that doesn't work I'm going to swap valve bodies with the spare beat to death one I have.

I had zero issues with the feed neck.

[glaman5266]

What gas were you using? Did you remove the x-chamber or keep it on? Just curious.

[Myrkul]

Update:

After getting to the field and chronoing, I still had to use the red spring to get it up to 285, but it did get there! I played most of the day with it and it rocked! I'm not quite satisfied using the red spring so I'll keep tinkering with it and will report back if I figure out why this one is so stubborn.

[Axel]

A little judicious electrical tape fixes this all up

[Gradyfest]

So the only way you can really play and not worry about your loader falling off is with a 68 Carbine is the metal feedneck. Well, there was one day I played all day with the plastic one, but I had to be conscious of it and could not tilt the gun to the left at all until the loader was like 1/4 full. But then another problem with the metal one besides the weight, (HEAVY) is you have to have just the right hopper. The metal ones do not compress what so ever. The tightening screw on it is almost literally there for looks. You really have to have that little metal “sawtooth“ piece on it to work.

Not all my Pro Carbines are loose at the forward grip and feedneck. Some more than others. But it’s not a big deal at all. It reminds me of M16s and M4s in the Marine Corps. The lower and upper receivers in the military are loose just like that, lol. You don’t notice it after a while, and it doesn’t affect function.

[Chappy]

Procarb all day long. Some of them have a bit of wobble as mentioned but I have never thought of it while playing a game. And if it really does bother you it can be mitigated.

[Meleager7]

The biggest advantage I see in the 98 + is that the triggers got better. The 98 and 98 custom had really good trigger pulls for out of the box sear trippers. The carbine series were a bit more crunchy and not just because they were mostly single triggers.

People that have spent more time with them, how do you like the pro carbine feed system with the shroud integrated vs the 68 carbine system?

The 68 Carbine feedneck was more solid on the gun. the Shroud Feedneck from the pro am / pro lite / pro carb can tend to have wobble, which you really notice with a loader on the gun. But it can be fixed by building up the gap between shroud and body with extra material. I used metal foil duct tape on my pro carb to get rid of any wobbling.

One other difference I noticed now that these many years have passed is that 68-Carbine Feednecks either were prone to breaking, or were easily lost...because i have seen countless examples of 68 Carbines being sold, and missing that feedneck! i'm not entirely sure of the story here, but my feedneck was absolutely solid the couple years I had my 68-carbine, it held up fine.

[Cunha]

The biggest advantage I see in the 98 + is that the triggers got better. The 98 and 98 custom had really good trigger pulls for out of the box sear trippers. The carbine series were a bit more crunchy and not just because they were mostly single triggers.

People that have spent more time with them, how do you like the pro carbine feed system with the shroud integrated vs the 68 carbine system?

[Meleager7]

Oh and my vote is Carbines over 98s all day. They are the last real quality gun Tippmann made. You get the same CVX in the 98s and A5s but in a quality machined aluminum alloy receiver over cheap pot metal cast receivers.

Agreed (although i have a soft spot for the shark gill Model 98) ! ......and the 68-Carbine/Pro-Carbine detent change is so much easier, as is replacing hammer seals, main springs, rear bumpers, etc.

Imagine if Tippmann decided not to switch to castings and stuck with machining parts, and then improved upon the Pro-Am /Carbine design? Would we have seen Vert Feed carbines? Electro Sear Tripper carbines? Low pressure, high volume carbines? It could have been pretty cool !

[Myrkul]

This....is most likely what happened. The adapter was only slightly tapered, but directly on the "top" there was a significant lip that was designed to pinch an "o" ring between the top of the adapter and the bottom of the valve. I don't think it is possible to screw it on tightly enough to pinch the valve spring without destroying the valve, but I think it was definitely screwed on tight enough to malign the lip on the adapter piece and restrict airflow. Once I drilled that lip off is when the velocity improved.

Either way, I should hopefully get a chance to chrono it this weekend and will report back!

[Myrkul]

I checked the front bolt, it certainly looks used but not really more so then expected. I did check the linkage arm hole and it has not yet worn though. Power tube was round and smooth. I borrowed a buddies 16" A-5 barrel and the velocity was no different. So I really don't suspect that the barrel is causing any issues. (That and I love these 8" lapcos on my tippmanns)

[Rolling Thunder 67]

Quick ?, is the hole in the CVX valve tapered,if i remember correctly it is, along with the adapter fitting. At one point someone may have over tightened the fitting in the valve to stop a leak and pinched the spring with point of the adapter fitting in the valve body. I mention this as you mentioned when you enlarged the hole in the adapter fitting and replace the seal you had a noticeable increase in velocity. You may have inadvertently corrected the velocity issue with replacement of the seal . i mention this as i had a 98 that i was asked to tech and found that someone had drove the airline so far into the valve that it pinched the spring and wouldn't allow it to move freely in the valve body. i know the hole for a 98 is straight which allows you to over tighten the airline very easily, causing the binding of the spring. Might be worth keeping in mind if you continue to have velocity issues.

[Gradyfest]

The metal 68 Carbine feed is really heavy and you will feel it on the gun. It also wears its mark on the receiver with use as the steel moves against the aluminum. The plastic one is just way soft and falls off literally by slightly angling the gun to one side with a full hopper.

The Pro Carbine solves all this and also you gain the ability to slide the front grip including feed forward. You now have fast access to the breech to run a pull thru squeegee without taking the barrel off. Slide the handle back again aligning the feed and your back in the game.

68 if you’re running a exp chamber or vertical and don’t need the front grip though. Pro Carbines with the front grip and a exp chamber grip look funny to me.

[Gradyfest]

Oh and my vote is Carbines over 98s all day. They are the last real quality gun Tippmann made. You get the same CVX in the 98s and A5s but in a quality machined aluminum alloy receiver over cheap pot metal cast receivers.

[Gradyfest]

Nice Carbine! I have almost a couple dozen 68 and Pro Carbines now, love them! The 68 Carbine CVX is the Pro Carbine CVX, one in the same. It’s pretty rare to find a 68 Carbine with the old floating rope valve, and only on early serial numbers, fun FYI. Anyways, there are only two parts in the Carbine CVX valves that are the same and interchangeable with the 98s CVXs. Those parts being the valve stem and the front valve seat.

One thing that can happen and they fixed the design with the 98s is that the front bolt can get a hole worn in it from the linkage arm causing drag on the power tube and velocity issues. I’ve seen a couple rental power tubes with a actual notch in them from the linkage arm passing thru the bolt. You shouldn’t have to crazy modify these or open up the valve like you did to get velocity. Did you try other barrels, don’t know if that short barrel is helping?