LouM:
The action should be a good one to work with. The rifle was an attempt to bring the Roller in to the new century with a modern cartridge and imitation gun powder. The steel is of better quality. The extractor is good, but the Swedish and Danish actions had a better one. The firing pin is of an adequately small diameter, saving you from making that modification.
The smokeless actions had a larger barrel shank diameter than the earlier actions, which make it a little touch and go for the octagon top. You really should add metal to the receiver ring rather than cut it away for the octagon.
The action certainly would be up to either chambering you are considering.
Howsomever, you are going to have a tough time building the rifle you desire at the price you suggest without doing some of the work yourself. One thing you might consider, if you have the inclination and some basic skills, is to look into the summer gunsmithing courses offered at many of the schools. There are classes at Trinidad State Junior College in Colorado on single shot metalsmithing, stockmaking and a number of related subjects. They are generally two week courses and are set up to allow the student to work on his or her own project under adult supervision. All things considered this may not be the cheapest route to a new rifle, but for many being able to build their own rifle is, like, way cool.
Glenn
