I am new to shooting and just recently purchased a Glock 19. I was curious to know if there is such thing as breaking in the barrel. Is there any procedure for selecting ammo or cleaning that I should follow when shooting my gun for the first few times? Any advice would be appreciated.
As far as I know there is no break-in for a barrel. One thing that is recommended by Glock is to us a copper cutter such as Kleenbore No. 10 Copper Cutter to counter the effects of jacketed rounds leaving copper residue in the barrel. Also Glock recommends factory loads and that is all I shoot (just because I do not reload).
With respect: Please read the manual first, before doing anything.
Glockamania brings up a good point. For example, the Glock manual is littered with jargon instructing NOT to use lead cast bullets because of the polygonal rifling. Use copper jacket ammo only. This is contrary to hundreds of thousands of grooved rifled barrels out there which can handle 100% lead cast bullets just fine, but polygonal rifling just doesn't like lead on its walls (if I had to guess, I'd say there's too much friction against the lead bullet, and being lead is relatively soft, the bullet deforms before it exists the barrel). I've actually seen people complain in their ammo reviews saying "my Glock shot these XXX brand semi-wadcutters like crap! I will never buy again!!!" Uh....
The Glock is a tool, but nonetheless a lethal one. Definitely read the manual for a tool of this caliber (har har har, see what I did there??? )