Carbine RT - How To Guide

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   So i got bored and put an old 98 Custom RT into my pro/carbine. I had
the foresight to take lots of pictures, so im writing a guide on how
you can fit a RT into your carbine. Its great fun to shock people when
the "newb gun" starts ripping.

Before you begin, be aware that this WILL void your warranty. This will
void your warranty so hard that Jesus himself wouldnt work on it for
free. This mod involves grinding and drilling on your guns reciever. It
also involves modifying the RT itself to the point that it will not
function correctly in the gun it is made for. If your not comfortable
with that, and with the use of a hand drill or drill press, a dremel
tool, and thread taps, DO NOT DO IT! Im not responsible if you cant
read a ruler and mess up your gun trying this, so dont cry if you fail.

This mod requires that you own a Pro/Carbine, or a 68-Carbine with the
CVX valve. If you do not have a CVX valve gun THIS WILL NOT WORK SO
DONT TRY IT. This mod also requires that you own a 98 Custom RT kit
complete with the cylinder, fat hose and barb, fat hose 90 degree,
limiter valve, 1/8 hose, and 1/8 hose banjo fitting. Basically
everything that you get with the 98 Custom kit.

Things you need:

-Pro/Carbine or 68-Carbine with CVX valve

-98 Custom RT Kit

-A dremel tool or equivalent

-A drill press or hand electric drill

-A 5/32" drill bit

-A 10-32 thread tap

-Safety glasses

-A breathing mask or bandana or towel

Maybe/Optional:

-X-Acto or pocket knife

-Carbine valve reduction fitting o-ring

-A cold beverage

To start with, completely strip your gun down to the bare reciever.
Remove the valve reduction fitting and the velocity screw then use a
pencil or dowel rod to push out the powertube and valve out the back of
the gun. You can leave the ball detent in, it doesnt get in the way.
Also completely open your grip and strip it down to the bare plastic
frame. Use some pliars to remove the pivot and spring pins inside,
remove the bottomline nuts. The grip nuts can stay in, as they seem to
be held in by nuclear glue.

My gun completely stripped to the bones.

Now for a list of things we will need, and what will be modified beyond repair.

Pictured is the 98 Custom RT kit, and a carbine valve reduction fitting
o-ring. The o-ring MIGHT not be needed. When you removed the valve
fitting from the underside of the reciever above, if the tiny o-ring in
there came out chewed up and nasty looking, you WILL need to replace
it. Sometimes it comes out in decent condition and you can just flip it
over.

These are the parts that we will modify. The reciever will be possible
to be changed back to stock with the addition of a modified bolt that i
will explain later. The grip panels will lose the trigger spring pin,
and will NOT be capable of being used stock without some special
modifying. The RT cylinder will be modified to the point that it wont
fire correctly in a 98, and the fat host and its fittings will be cut
to size.

Now begins the actual mod. The first part is the worst part in the
entire job. It sucks, you will hate it, and it will drive you nuts. But
patience is required, because if you mess up youll have to buy new
gripframe halves.

I used a dremel sanding bit and a dremel grinding wheel for small areas
to grind out the cylinder shaped groove for the RT cylinder. The
plastic will melt very fast, which isnt too big of a problem as long as
you keep stopping to peel away the melted crud, if you leave it in it
obscures the work and makes it harder to see what your doing. Go slow,
make sure you cut the groove in straight and evenly between the hole
for the grip half bolt, and the grip panel nut. Theres BARELY enough
room, and for this to fit correctly, it will be very thin. This is
where patience comes in, if you get annoyed and go fast, youll melt a
hole straight through the side of the grip. Im a very impatient person,
so if i can do it, anyone can.

I strongly advise that you use safety goggles and some sort of breath
mask, even if its just a towel tied over your mouth and nose. Cutting
this out throws hot plastic fragments and dust all over, you do not
want that in your eye, or in your lungs.

Here is the right half in progress. Its getting close.

Note that you will have to thin out the ends because the cylinder is a
bit longer then there is room in there. If the grip starts getting hot,
switch to the other half and work on it for a bit. Make sure that you
cut both grooves in the same place! You can cut up or down a bit, as
long as it fits, but both sides must be the same or they wont fit
together around the cylinder.

The cylinder sitting in the right side groove

You can guage your progress by the little machining bump left in the
center of the back end on the cylinder. Lay it in and look and see if
that bump is getting close to even with the grip half inside edge. The
front is a bit of guesswork, as the shaft from the cylinder will fit
with a bit of space around it, so dont cut your groove to where the
shaft is against the grip edge, thats too deep.

Now another somewhat annoying part. You need to make the fat hose that
rises up from the cylinder fit. Im sure you noticed its WAY too long,
we can fix that. Pull on the fittings and the hose should pull off. Use
some needle-nose pliars or something to pull the hose off the other
fitting. Now, look at the hose barbs. You will see they have a long
tube shaped section, a flare, then another tube shaped section. Theres
no need for the extra length, so were going to modify the barbs. Use a
grinding bit in your dremel to grind the barbs down so they end right
at the end of the flare. All we need is for them to hold the hose on.
Do this for both, then cut the hose to fit so the barbs are touching.
This should result in a very short hose with a fitting on one end, and
a 90 degree fitting on the other.

We also need to modify the grip more to fit this hose. Lay the cylinder
in the slot and mark where the hole in the top is in relation to the
grip. Put a couple of the pins back in and stick the grips together.
Now, clamp the grip in a vise and drill a hole down from the top on
your mark, so the hose has a slot. Now using a small bit, drill a pilot
hole for the 90 degree fitting to stick out through. This should end up
right around the ledge area on the outside of the grip. Heres a picture
of mine

Notice the large hole i drilled for the fitting. The fitting sticks out
through this hole a bit and the limiter valve screws into the 90 degree
fitting. It should be pretty secure, and look like this from the other
side

Test fit the 2 grip halves with the cylinder in place. Make any
adjustments you need in the groove you cut so the cylinder is held
securely in place, but the grips still fit together good. Once youre
done with that, the grip section is complete!

Now for the part that takes guts. Drilling a hole in the side of your
gun. The reason RT and the cyclone feed work is a property of the way
the CVX valve functions. 

The CVX valve. From Matt's Procarbine Page.

Notice the cut area on the left of the valve, just to the right of the
o-ring. If a tap is installed in the gun right there, a strong burst of
air will come out. If you tap the valve anywhere else, this will not
work. So we have to be VERY careful where we put our air tap. If you
want to see how you figure it out, keep reading, if you just want to
know where to drill, skip ahead a bit.

To figure out where to drill, put the valve back in the gun, stick a
ruler inside the gun, until it hits the back of the valve. Write down
that measurement. Now remove the valve and look at it. Measure from the
back of the valve, to a point centered on that cut in the back of the
valve. Add that to your previous measurement.

You should have gotten 4 9/32" as your measurement. If you skipped the
previous paragraph like a lazy bum, we will be drilling our hole
exactly 4 inches and 9/32 of an inch in from the rear of the gun body.
This is centered right on the channel in the back of the valve when it
is installed in the gun.

Measure out that distance. Measure it again. Measure it once more to be sure, and mark it with a sharpie or a pencil.

If your using a hand drill i strongly suggest you use a small bit and
drill a pilot hole. This needs to be precise. Once you have a pilot
hole in, drill it with the 5/32" bit. Now get your 10-32 thread tap and
tap threads into the hole. Be careful doing this. Make straight clean
threads, i advise you use a tap wrench to do it up right. Make sure you
clean the reciever out, dont leave any metal dust and other crap in
there, itll gum up your gun later. The banjo fitting from the RT kit
will screw right into the hole you just made.

Now it says "Safety instructions free fro". Cool!

Only a couple other things need to be done to get this working. If you
tried to put the grip on the gun, you noticed that it doesnt fit in the
back. Thats because that 90 degree fitting sticks up above the frame.
We need to grind down a bit of the reciever to fit. This doesnt hinder
anything at all.

Clamp the reciever in a vise and grind down this corner edge about
1/8". The grip should fit now. Put it on and bolt it on, make sure
everything fits and looks good. Trim your hose if needed, it should
look like this:

One last thing needs to be done, thats modifying the trigger to give
the RT room to work. Clamp the trigger into your vise and go to town on
the back of it with a grinding bit. We just need to flatten it off to
give a spot for the RT shaft to push. 

Once you have that done, the mod is complete! Reassemble your gun, gas
it up, and use the limiter valve on the grip to sweet-spot the RT where
you want it.

As for reverting the gun to stock, you will need new gripframe halves,
since we destroyed the hole that the trigger spring pin fit in. I
assume if you wanted you could easily drill a new hole and install a
longer pin, and be possible to revert the gun to stock. We also need to
plug the hole in the gun. To do this, purchase a 10-32 machine screw
from a hardware store, and cut it to about 1/8" of threads. The o-ring
on the threaded area of the banjo fitting can come off and be put on
this short bolt, which will function as a plug.

Hope it helps, happy modding!