I have been using a Grizzly G0709 14 x 40 for many years now. No complaints. Does everything needed for Chambering.
I'm sure that the other Lathes mentioned are just as good or maybe better, but I am only speaking from a one Lathe experience.
My Lathe will plug into 110V outlet- many others require 220V. This was a huge deciding factor for me.
As said before- the tooling is going to be more expensive than the Lathe.
To me this has been the fun part of the process.
All I wanted to do when I started out was to control the amount of time and choices in a rifle build..... I got tired of waiting on others to complete a custom for me. So I took the dive.
I currently chamber for a firearms manufacturer in my spare time, and I have a new trade/skill for my retirement!
Start off slow, procure your basic tools like, calipers, depth mics, dial indicators, mag tool holders- the list goes on and on. Make sure you spend the money on the good stuff. Browne & Sharpe, Starrett, just to name a couple.
Depending on the set up you will be using- will directly affect your choice of tooling.
I use the Viper set up in my 4 jaw to indicate the barrels so I don't have to use the out board spider. Awesome for chambering.
The Marine Corps armorers use this set up, as well as some of the operator armorers.
You can see his videos on You tube- he takes you through the entire process of chambering, and he sells the video from his website so you can review it for reference.
Just look up on the YouTube website- Chambering video part 1. wmv
His name is Bob Pastor- I highly recommend watching this if you are just starting out!!!
I also highly recommend John L Hinnant's book: THE COMPLETE ILLUSTRATED GUIDE TO PRECISION RIFLE BARREL FITTING.
You can get a copy of this book from Brownells. He is old school. But, the old ways are sometimes the best!
In my opinion, this is THE book you should ABSOLUTELY own for reference and all things chambering PERIOD.
Factually speaking: Before you buy your Lathe, you should purchase this book! Watch Bob's video's as well!!!
REMEMBER ONE OF THE CARDINAL RULES: THERE IS NEVER A HURRY IN A MACHINE SHOP!!