Yesterday my stainless steel M4 barrel arrived from PK Firearms.  May I just say that the barrel and service from PK was outstanding.  So I DuraCoated the barrel this morning and attempted to finish the installation of the barrel.  Installing the barrel went perfectly.  The barrel lined up in the receiver without any play and the barrel nut snugged up perfectly for the gas tube installation.  That's where everything went to shit.  I put the tube in and I must has tapped it in too far initially.  I remember looking into the roll pin hole on the FSB and I could see the part of the tube that has a small band cut into it.  I couldn't remember whether that can before or after the roll pin hole.  I tried to remove the tube by all conventional means, but the damn thing wouldn't budge.  So, after fighting with it for about 2 hours I cut the tube in half with a file.  The part in the receiver fell right out.  The only way I could get the front part out was by clamping it to a railing out side of  my apartment, bending the tube, and finally twisting the bastard out.  That damned tube is a lot tougher than it looks.  In the end, the only damage done was to my beautiful new finish.  I've since repaired it, but I think my spirit is broken.  Anyone have any pointers on installing a gas tube?  

Gas tube tool.  Brownells.  And a taper pin punch to align the holes.

go slowly for the install, u shouldn't need to force too much. Also use some CLP to make it easier to slide.
another gas tube is only 8 bux anyway..

Oh yeah, the cost isn't the big thing.  The bad part is that I can't buy a gas tube anywhere locally.  That means I have to wait for the parts to come from Midway.  Just another delay in the project.

The only barrels I ever had trouble getting the tubes in were 2 Rock River barrels. The hole in the sight base was tight and I ruuined a tube or 2 getting them in.
The last 4 DPMS gas tubes I got had the offset bent incorrectly. Not sure if they started out that way or got bent somewhere between them and me winding up with them. They did not have enough bend and the bend was not even. If you held them against a straight edge they were looking down a good bit. I got one from Bushmaster and it was ok.