About $500 and up.
Depends on which model and condition, condition, and condition....
Depends a lot on which one and original condition, condition, and condition!
Depends greatly on which model and more importantly ORIGINAL condition, condition, and condition.
In order to determine the exact value of a Remington Rolling Block rifle, a few different factors would need to be taken into consideration. Some of these things would be the age and condition of the rifle.
Civil War was 1861-65; obviously, the Remington rolling block came out later. Is it a military rifle? What caliber? What condition? All these things affect value. Ranges of rolling blocks are from $550-$4000.
Hexagon barrel what? Model? pump, rolling block, ?? Condition?
The Rolling block was made in 1907
In the year 1890,as a model No.4 rolling block rifle.
My research indicates about $300.00 in good condition, and that is for a model 4 in .32 long caliber.
Octagonal barrel could be a plethora of different guns anywhere from a rolling block to a pump. Need to identify what it is first and condition, condition, condition for values.
You will have to contact Remington.
Not enough information to even hazard a guess.