Well there's not a lot of information here to understand what exactly your asking but if it's E. Remington and sons it has to be prior to 1888 when it then became Remington Arms Co.
I have a octagonal barrel .32 caliber Remington Patent date May 3, 1864 - What would it be worth?
Which model, what condition?
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.
I too have a rifle matching this description. Any information would be of interest.
about two hundred and seventy five depending on condition
Just the barrel?
No
Go to http://www.remingtonsociety.com/forums/ and ask. Describe all the markings and provide pictures if possible.
A 243 calibre rifle is Just that. The bore (internal measurement of the barrel) is 0.243 of an inch in diameter.
No
Weight is the main factor
Depends greatly on which rolling block, there's to many to specify them all serial/date.