how much are they
A utility bolt action 12 gauge will bring from $50 to $125, depending on condition, at most auctions.
There were several different MAKES of bolt action shotguns, and the magazines do not interchange. If you repost your question with the make and model, we can give you a much better answer. IF the shotgun is a Mossberg (one of the more common bolt actions) you can check the website for Havlin Sales.
How much what? Weight, value, use?
50-100 USD
Up to $125.
25 USD
50-100 or so
Value seldom goes much beyond 100 USD
The asking price online for a used Revelation 16-gauge bolt action R316BKB is $100 to $140. The price partly depends on the condition of the gun and if anything, such as magazines, come with it.
From $25 to $125 depending on condition.
Moseberg. Not of very much value around 80-125 $.