Depending on condition, between $175-$275.
50-200
stainless w/scope 650.00
100-225 USD depending on condition, box, accessories, manual, etc..
Depends on model, barrel/sights, and condition. Anywhere from $100 for a well used Mk1 to $400 for a NIB stainless heavy barreled Mk II with target sights.
gatlin
Depends on the exact model finish, type barrel and sights, atc. AVerage from a low of $100 for a well worn but shootable to about $350-$450 for slab barreled target model in stainless.
$250-$500, depending on the EXACT model and condition.
A barrel is the part that holds the shot shell or casing that the bullet or BBs go down towards the target. In a Center fire rifle or pistol the barrel has rifling to help stabilize the bullet after it has left the muzzle
Depending on condition, type of barrel, sights, etc, anywhere for $150-$300.
$150-$250, depending on condition, barrel, etc.
Read the manual and follow the instructions. For the bore of the barrel, I would recommend using a BoreSnake.
300-700 USD