I'm trying to re-barrle a 25 year old M16, and I'm having trouble punching out the roll pin that retains the gas tube.  I imagine it's thuroughly caked up with carbon.  Is there something in particular I should soak it with?  I was thinking kerosene or tranny fluid would probably break up the carbon.  By the way, I was tapping it with a punch and a 32oz. mechanics ball peen.  I thought that would have knocked it out for sure.

I don't have an answer for you but I truely do feel bad for you.  If the roll pin is that tough, the gas tube itself could be a real bear!

Liquid wrench, a 1/16" roll pin punch and a bigger hammer!   Maybe some heat from a propane torch.

+1 on the torch been there ! ! !

Use liquid wrench, and make sure to let it soak so when it's time to get the gas tube out, it won't be so hard.  I had to use a cleaning rag and a set of pliers to 'gently' get my last tube out.

If you were to go out to your driveway and attempt to move your car without starting the engine, would it be easier to move if you:

a)  Hit it on the bumper with repeated blows from a 16# sledgehammer...

or

b)  Pushed it?

(Go on and soak the pin a day or so with some Kroil or other high quality penetrating oil.)

Ok, why beat it out when you can PRESS it out?  Here is how, shade tree mechanicing... make a pin from the shank of a drill bit the right size to go through the hole.  Set this aside.

With your needle nose Vise Grips, hold the pin positioned on the gas tube pin, and with your drill press press it out.  

Ain't THAT easy?

Quoted: If you were to go out to your driveway and attempt to move your car without starting the engine, would it be easier to move if you: a)  Hit it on the bumper with repeated blows from a 16# sledgehammer... or b)  Pushed it? (Go on and soak the pin a day or so with some Kroil or other high quality penetrating oil.) Ok, why beat it out when you can PRESS it out?  Here is how, shade tree mechanicing... make a pin from the shank of a drill bit the right size to go through the hole.  Set this aside. With your needle nose Vise Grips, hold the pin positioned on the gas tube pin, and with your drill press press it out.   Ain't THAT easy?

Well, I didn't press it out because the punch started to bend when using a vise.  Then I thought I would use something I could sacrifice....a drill bit.  When it snapped, it missed my face by about an inch.  This was actually done before the 32oz ball peen, which is why I implemented a hammer that heavy.  Sorry for not giving the enitre story.  This is one tough little sob.  I think I'm gonna go with some heat for round two.....round three will be the drill.