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You might need to investigate if you think the sights have been modified over the years. At first blush it would say you front sight is to low, however that does not rule out load like bullet weight speed, etc. I personally would wait until you could try the rifle at 100 yards. I say this because the math to correct is easier if done on 100 yard results. (Just my way of mentally calculating solutions. smile ) Generally thinking load and speed are not the major contributor to the results. Physical sight heights being that major contributor.
Shoot the rifle a few more time as it is and get a better understanding of what is really happening here and then make corrections as needed.
As you may see I also am working with one of these great 2 barrel rifles. So much fun. Can't hardly wait till winter breaks and I and my good friend can shoot mine. Maybe if it shoots really well he will take it on his Elephant hunt he is going on this spring. LOL smile just for you Rick.

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Or maybe your bullet is too heavy or it is spending too much time in the barrel and recoil is raising the muzzle before the bullet exits. If you want to check the sights use the original 136 grains of black powder as a test. You might also try the other standard bullet of 340 grains.

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I'll try the other bullet but I'm not using black powder. I hate it.

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Originally Posted by Mike Harrell
I'll try the other bullet but I'm not using black powder. I hate it.
A couple thoughts, does the rifle's front sight look original or may have been changed at some point in it's life?
And I suggest you do a little measuring of the height of both the front and rear blade sights above the bore centerline. Then the distance between the two sights. With a little math you can calculate whether the sights are reasonable or something is wrong. (If you want any help with this PM me and I can help)

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top of front bead to best guess center of bore is .522, from top of rear blade to center bore is .590, top of blade to bottom of V is .045. Distance from rear of front bead to rear blade is 22 3/8" Front sight is original.

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Basically, with the top of the front sight even with the top of the rear blade there is a difference of .068". With 50yds (1800") / 23.375" * .068 = ~5.2". That means when your sighted on the target the barrels are pointing 5.2" above the target center. That seems quite reasonable. But as you know your bullet impacts are quite a bit higher which would indicate the muzzles must be recoiling up due to recoil before the bullets leave the barrel muzzles.
I would try the lighter bullet and get the velocity up a bit higher. And experiment with the sight hold relationship between front and rear.

Last edited by LRF; 03/18/22 03:38 PM.
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will do. I have a mold coming for the 340 grain bullets. And the 57 grains of 4198 is in the middle of the low to max range of load. When it's warmer I'll break out the chrono.

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Mike you got me thinking so I decided to measure my sights on my 450 3 1/4" BPE. The sight difference front to rear is .064" and they are 21" apart. Which means at 50 yds the barrels are pointing ~5.5" above the aim point.
When the weather breaks here and warms up I will go shoot it. However, for reference, my first loads will be 120 grains of black pushing a 270 gr hollow point copper tubed paper patch bullet.

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measured to top of rib there is .056 difference in height.

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Typically I measure from the underside of the barrel to the top of the sight then subtract half the barrel diameter at that location. Then subtracting the front sight height from the rear establishes the angle of cant between the line of sight and line of bore. Just the way I do it. smile

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