27 May 2015, 10:09
Todd Williamsquote:Originally posted by MacD37:quote:Originally posted by Bill73:
Todd,
so did the increase in barrel weight result in increased velocity for the regulating load or decreased velocity?
Bill I understand your question was to Todd, and he did have a real time getting his rifle to shoot properly after mounting the scope.
The reason was the addition of a scope and mounts will not effect the speed of the load you are using.
The reason it changes the point of impact is because the weight of the scope and mounts is above the barrels and depending on the weight of the scope and mounts and how high it is mounted, this tends to retard the natural muzzle FLIP.
When a side by side double rifle is fired the barrel being fired tends to move away from the other barrel and up at a different amount than it did when fired without the weight.
When a properly regulated double rifle with the iron sights pointed at the aiming point on the target, the right barrels line of sight will actually be pointed at a place on the target that is low, and on the left. As the recoil flips the muzzles that barrel will move up and to the right, and when the bullet exits the muzzle it will be pointed at where the sight was pointed when the trigger was pulled, and vice-versa for the left barrel.
When weight is added to the top of the barrel set depending on how heavy the scope and mounts are and how high they are above the barrels the more or less the muzzle flip will be retarded so that the bullets hits the target differently than it did from the barrels without the extra weight. The velocity of the load will not be changed, but the muzzle flip will!
When mounting a scope on a s/s double rifle it should be as light and as low as it can be and still line up with eye, and as strong as it can be to take the punishment of the recoil of the rifle being used!
Todd put in a lot of time, powder and bullets to find a load speed that would overcome the adding of his scope. In his case he found a good load that let him shoot a wart hog right between the eyes at some distance with that rifle!
I'm about to get into the same situation because I now must mount glass sights on all my doubles because of an eye problem.
Good luck Bill!
Mac stated it about as well as can be said.
Just one more point of clarification however and that is that the actual velocity of the load is not what had to be modified in my "scope load" but rather I had to find a combination of powder speed / bullet weight and design, i.e. acceleration rate up to that design velocity, that caused my bullet to remain in the barrel for the necessary time to exit at the appropriate point in the recoil arc. In other words, as Mac described, adding the scope added weight which slowed the recoil arc, so I had to find a bullet / powder combination that accelerated to design velocity at a slower rate allowing the bullet to remain in the barrel longer.
I used this analogy a few times in the past but I'll do so again now. Think of two drag race cars racing each other. They may both cross the finish line at the same exact speed but one may get there quicker than the other does. That's a difference in accelerate rate.