One may consider it counter intuitive but moving right for the right barrel projectile and left for left barrel projectile is caused because the time the projectile spent in the barrels was too long (too long a time period in barrels allowing right barrel to be moved under recoil to the right and movement to left for the left barrel while the projectiles are traveling down the barrel); therefore the projectile speed needs to be increased to have the projectiles exit the barrel sooner during the time the barrels are moving away from each other under recoil---then the projectiles will be nearer the center of the target.
Graeme Wright in his book SHOOTING THE BRITISH DOUBLE RIFLE goes into significant detail in the explanation of developing loads that will work in the original setting of the barrels by the maker to the makers load for the rifle. Black power as well as nitro powder.
My experience in regulating (moving the barrels right/left and up/down and soldering them in place) as well as developing a load after a DR has been regulated has shown to me that all sorts of issues with the projectiles will cause the shots to be off target--not just the changes in velocity as a result of more or less propellant in the cartridge. In one double rifle I built it shoots flat nose projectiles with great accuracy--at 100 years the right and left touch each other right to left, but with round nose projectiles the shots are all over the board. My take is that the round nose projectile surface area that contacts the bore is different than the surface area of the flat nose one and that is where the difference is not the shape of the nose. If the barrel had a different rifling twist rate the flat nose projectile may be all over the target.
CJF is approaching the task with thought and diligence which is prudent and he will get the desired results.
Kind Regards;
Stephen Howell
Last edited by bushveld; 12/31/24 08:53 PM.
