I know bending smoothbore barrels has been a common practice for adjusting POI (point of impact) ever since people first started shooting smoothies,... but I ran across some information that I wasn't aware of, that was also used to change a smoothbore's POI to a lesser degree.
quote:..... "First, I am all in favor of bending barrels to correct larger errors in POINT OF IMPACT(POI).
Filing the muzzle is to make the changes:
a. If you can't bend the barrel for some reason( as in DBL shotguns- where you are concerned with breaking the solder between the barrels, or where one barrel is more off- or off in a different direction than the other); and
b. For small deviations for the POI from the POA (point of aim).
For my purpose, I am treating this subject as if we are using a DB shotgun, so that the bead is held at the 12 o'clock( clock dial) position to the target.
Now, lets assume the LEFT barrel( Your left as you look down the barrels from the butt stock) is shooting LEFT- to 9 o'clock, and the center of the pattern is 12+ inches off from the POA.
You want to move that shot so that it more closely impacts the center of the pattern at the POA.
WHAT TO DO:
FILE THE LEFT BARREL MUZZLE AT 9 o'CLOCK. It sounds counter intuitive, until you think about what is going to push that shot one way or another. Its the Gases pushing the shot, and wads or cards behind the gas out of the muzzle that will move the shot in one direction or another. By filing the muzzle at 9 O'clock, GAS will Escape out the muzzle at 9 o'clock FIRST, and push the wad and shot towards 3 o'clock, moving it in that direction to get closer to the POA. The more you file the muzzle, the more the load of shot will move in the OPPOSITE direction.
Some DBL shotguns are constructed so that their patterns actually cross( we see this also in Dbl. rifles).
IN those cases, sometimes it simply makes more sense to break or cut the solder between the barrels and use wedges near the muzzle to push the barrels away from each other. When you have the barrels shooting patterns to a similar POA, THEN re-solder the barrels and ribs.
However, I have seen many OLD barrels on DBL shotguns that have been filed in the middle of the two barrels, so that the shot patterns move away from crossing over each other, and shoot to a similar POA. The muzzles of those barrels have a half-moon, or "half-round" profile , under that front sight. Some old guns that were big, 10 gauge duck and geese guns- way too heavy to use on upland game--- had extremely pronounced filing marks on that work- leaving no doubt how the arc was made.
Lets assume your left barrel is shooting to 9 O'clock, as above, but the Right barrel is shooting Low Right- at 4:30 O'clock. You would file the left barrel's muzzle to move the pattern to the right, as described above. Then, on the right barrel, you would file the muzzle at 4:30 O'clock to move the pattern UP and LEFT to your POA."
Topic: Adjusting smoothbore POI (Read 407 times)