I'm fairly new to the AR-15, and working on upgrading my weapon.

I have a Bushmaster carbine w/ a 16" barrel and intend to put a Troy 13.5" MRF-RX rail system on it.
My question is can I go to a mid-length gas tube just by switching tubes and having my gas block mounted in the
appropriate spot? And will I notice a real difference in handling or reliability?

Thanks for your help!

Here's a pic of my carbine for the heck of it...
http://i341.photobucket.com/albums/o364/chasemonson/Rifle001.jpg

Short answer to the ? asked.  No.

In order to do what you suggest the old gas port in the barrel would have to be welded and a new one of the right size drilled at the new location.

You'd do better to get a barrel set up for mid gas and sell the old one.

You would likely notice a huge difference in reliablity by converting your exisiting barrel because odds are the gas system would not be set up correctly and you'd have an unreliable weapon.

By converting to a new barrel, you likely would notice very little difference although some as the recoil impulse is milder.

Just mount a lo-pro gas block on that barrel.  Install the rail over it and add a rail mounted front sight if that's the look your going for.

There is a hole in your barrel underneath the angled leg of your front sight base.  If you move the FSB forward, you would have to plug the carbine length hole in the barrel.  You could shave down the FSB, just above the gas tube so a rail could go over it.  Then install another FSB at the mid length distance.  That might take some fancy machine work.  The barrel steps down slightly forward of the FSB.  Also there would be an issue mounting the front leg of the mid-length FSB on the M203 step down.  It would be far easier unless you have access to and the knowledge to use, a full machine shop, to just buy a mid-length upper.

Scott

Awesome. Thanks for the help!