leshiy price question! suggest me price

The main reason not to buy a used gun, is because a lot of people don’t know you’re not supposed to clean them with a metal cleaning rod, so they jack up the barrels. And equal number don’t know that you’re supposed to clean them at all when you get them so they shoot their guns with all that grease packing stuff in there and ruin the barrels accuracy. I only buy a used gun if I ask certain questions and find out how they cleaned it...without leading them, I try and find out if they used a safe pull through patch system. When I find someone that did, I can tell they know what they’re doing. You can get some great deals on used guns. I just got a red wolf , only shot once, with a $500 Aztec scope and 8000 pallets JSB for $2000. Super deal. 
 
And equal number don’t know that you’re supposed to clean them at all when you get them so they shoot their guns with all that grease packing stuff in there and ruin the barrels accuracy.

Please explain how grease damages steel and if you think the barrel is ruined forever.

Do manufacturers include a warning not to fire the gun without pull through cleaning first?