I have never heard that Glock barrels are NOT heat treated. Could be true but I doubt it. The primary problem with Glock barrels is the feed ramp undercuts the chamber significantly causing what is called an unsupported chamber. When accidents happen, the brass lets go at the bottom back of the case and blows down. I have seen photos of catastrophic failures of Glock barrels that peel open upward. This is most likely due to leading in the polygon rifling causing pressures to spike. Some have reported such failures even though lead ammo was never fired through the gun.
Aftermarket barrels are a very good idea, especially if you want to shoot inexpensive cast bullets through your Glock. Reloading for the 10mm is pretty straight forward. I load for a Smith & Wesson 1006 and get some very good groups. I shoot IPSC with this gun with handloads to 175 power factor (175gr bullet @ 1000 fps).
Reloading glock fired brass is somewhat problematic. Many cases will have a bulge at the base where the feed ramp was in relation to the case. This bulge can be slight (in low pressure rounds) to pronounced (in higher pressure rounds). It must be corrected to insure proper feeding/chambering. There are two machines that will correct this condition. The Case Pro and the Case Master. I happen to have a Case Master and it does a wonderful job of returning the brass to factory new specs. I can process 9mm, .40, .357 SIG, 10mm, .45 ACP and .400 Cor-Bon.