Just wanted to +1 the threads below, which just saved me a bundle (thanks A_Free_Man and Prebandanna !):

http://www.ar15.com/forums/topic.html?b=3&f=4&t=554970
http://www.ar15.com/archive/topic.html?b=3&f=4&t=147940

I was replacing my handguards/delta ring/gas block/barrel nut on my RRA mid-length with a Troy TRX standard last night. I had received my rail from cheaper t d, but had not yet received my upper vice block (arrived today). Thinking myself smarter than conventional wisdom, I clamped my upper to the workbench using wood blocks. Upside down, with the top rail on the bench (wooden bench), 1x2's on top of the upper, and all clamped down. Please don't laugh. Or better yet, laugh to yourself, I was overeager, and now know it was plainly a bad idea. Anyway, during the loosening process of the factory barrel nut, I must have bent the thin piece of aluminum under the ejection port. I found out once I dropped the bcg down the upper, and found it binding.

Anyway, the article above got me straightened out (lul), and the bcg now slides up and down without binding, nor newfound play. I thought it worthile as a cautionary tale to others who would try the same thing. Don't. Get a proper block for the job.

Specifically how I did it was to clamp the upper, upside down in my vice, cushined by the same 1x2's. I wrapped two 14-15mm wrenches in duct tape, and stuck a screwdriver in the front lug hole. By slowly and repeatedly:
- Sliding the bcg down to see where it binds
- Marking with a crayon
- Flexing the bent rail
I was able to bring it back in line. The only thing I did differently was to flex more diaganally than laterally, to bring the spring ejector rail up (up in the vice, becuase the upper was upside-down in the vice) as well as out. I did this by inserting the wrench through the ejector port, and leveraging against the top of the vice.

It would have been really easy not to post this, but I wanted to thank those who came before, and hopefully caution others.

"it would have been really easy not to post this, but I wanted to thank those who came before, and hopefully caution others".

Very cool

You're very welcome.

You haven't really "repaired" it, you just bent it so the carrier doesn't bind.