Lead ?

[Kurt]

Your not going to hurt that barrel shooting lead bullets unless you don't do a thorough job cleaning it. If you leave lead smears in the bore that covers up the powder fouling and if you leave the rifle set for a spell that fouling will start etching the bore.
As far as the lead rings. You will find them using a GG bullet with the 45 degree chamber end after just about every shot. Some say they don't get lead rings because my brass fits the chamber. If you take a cleaning rod with a gore guide and carefully push it from the muzzle with a snug fitting patch chances are you will have a ring on the patch when it clears the chamber.
You can avoid the lead ring if you seat your bullet with the lube groove just in front of the case mouth so it is over the gap of the chamber end and when that bullet gets bumped when the charge goes off the lube will fill that void between the case mouth and the lead.
You can check this out pretty easy using a bore scope or a cleaning patch from the muzzle as mentioned above.
Clean the rifle good after your done shooting and it will last as long as you have it.
You can check a clean barrel by pushing a couple snug dry white patches through and if you have gray streaks on that patch you still have lead in the bore. It the bore is clean that patch will come out just as clean as it went in.

Kurt