Originally Posted by dkf
You are not going to get a fully supported barrel for a Glock, well at least not one that will function. There is going to be an area at the feed ramp that is not going to have full support, just the way it is. The later .40 glock barrels like in your Gen 4 have more support than the older .40 barrels. If it were me I would shoot them one a time and examine the brass. A small convex portion near the unsupported part of the chamber is normal.
If you get something that looks like the pic below you do not want to shoot any more.
I disagree. There are aftermarket that are fully supported and will function fine. It cause cause feeding problems. But it can be done. Most venders now just offer better support. Tig weld the ramp and recut it. U can get fully supported that way.