New rail receiver for AR-15

[FatalMove]

I have an AR-15 with a2 suitcase sights and i want to change the receiver to the rail type. How involved is replacing the barrel on the new receiver? i have looked for a gunsmith to do it for me but i have been unsuccessful in finding one.
Anyone know of a gunsmith that can do it in the Nashville TN area? I can generally repair stuff. So... can anyone walk me thru it? I understand i must remove the gas tube. But it seems very tight. i removed the pin how careful should you be or how much abuse will it take with pliers and the like? After its off i must turn the sprocket looking nut with the proper tool. I got the general idea but what about headspacing? Anybody got any ideas?


FataL][V][ove

 

[Bruce333]

All your questions have been answered here. Build it yourself on AR15.com (doesn't make sense to me to try to repost it all when it's been covered already )

If you don't want to do it yourself, you might find someone that knows a smith here: http://www.ar15.com/forums/forum.html?b=8&f=38

 

[Spreadfire Arms]

i think you are asking how to change the upper receiver from A2 to A3. im assuming you purchased an A3 upper receiver with the forward assist and ejection port cover already installed?

first remove the handguards.

you'd have to put the upper receiver in some sort of padded vise or block. you have to use a punch and hammer to remove the roll pin that holds the gas tube to the front sight post, right to left. then pull the gas tube towards the upper receiver until it leaves the front sight, rotate it 90 degrees so the bend in the gas tube clears the front signt post, and then remove it. then use an AR15 armorer's wrench to remove the barrel nut which is located under the delta ring. remove the A2 upper receiver from the block or vise and put in your A3 upper receiver. insert the barrel and make sure the feed ramps on the upper receiver (if it has M4 cuts) line up with those on the barrel. tighten the barrel nut and make sure it lines up with the gas tube hole in the upper receiver (and spring in the delta ring). re-insert the gas tube into the upper receiver. rotate it back 90 degrees and make sure the gas orifice is pointed down. slide it back into the front sight post and re-align the retaining hole in the gas tube with the hole in the front sight post. re-insert the roll pin right to left. re-attach handguards.

that's the basic gist of how to do it. if it sounds too complicated seek an AR15 armorer.