There is no point in cutting BLOwith turpentine, it will dry too fast. Since RLO is slow (very slow) drying it allows you time to work the dirt and grime out of the stock. I would not use BLO
cut with turpentine to clean a rifle stock; it would be good as a base on a new stock because it would allow the oil to penetrate deeper into the wood, but not as a cleaning agent. BLO has driers and hardeners, some pretty toxic, its not what was used on the stock from the armory, and if it has it on it already it was done after the fact. The BLO is also going to make it shine more than RLO. It's really a personal preference. Just a warning though, if you don't get the gunk and dirt out first before using BLO you are going to play heck after it dries getting it out.
You will not find in any US Military handbooks where BLO was used on service rifles; All of them will reference the use of RLO every month or after getting wet or in the rain rubbed in by hand (If anyone has a US Miltary reference that indicates BLO, I would ask if you could tell me which manual because I have been looking for a reference for years). Using RLO by itself is a cleaner if applied and then wiped off with a rag.
But like I said, it's all a personal preference and it only going to be the collector who is going to pay attention to that detail.