Congratz on the Glock 21! She's a fine weapon.
I agree with DrumJunkie on your ammo question. Try different brands until you find one that works best with your pistol.
"Blessed be the Lord my strength, which teacheth my hands to war, and my fingers to fight." -Psalms 144:1
That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved. - Romans 10:9