Kodiak Barrel Regulation

[Bearbait2]

Filing the muzzle to move point of impact: IT DIDN'T WORK FOR US.

Kodiak .72cal
Used two different PRB sizes. Used different patch thickness.
Tried Goex 2F, 3F and Pyrodex Select. Tried powder charges in increasing increments of 5 grains, from 90gr to 125gr; 5 shot groups.
Burned over 1 1/2 lbs of powder.
Test was conducted over a period of several days.

All groups shot to same point of impact, left barrel relative to the right barrel.
The PRBs cross at 15 yards and the left barrel also shoots several inches higher than the right, with the same sight setting.

After establishing POI (point of impact) with both barrels, single sight, commenced to remove a small amount of metal from the muzzle of the left barrel; in an attempt to move the POI to the left and down. After each removal, would fire a 5 shot group. You can see in the photo how much material was removed by the end of the test.
IT DID NOT MAKE ANY DIFFERENCE in POI, left barrel relative to the right barrel.

Perhaps this is due to the lower pressures developed by BP as compared to smokeless?

Interesting thing, group size from the left barrel gradually shrunk from 5" to 3" at 75 yards, as metal was removed. Go figure.

Anyway, we now have the left barrel sighted in for 100 yards and the right for 50 yards, using the factory sights. Muzzle doesn't look pretty but it shoots fine!
Best Wishes

 

[paulvallandigham]

The only way you would change the POI of Both Barrels( where they meet- you said at 15 yds.) would be to free the barrels from each other, and then wedge the barrels further apart. That would extend the range where the two barrels shoot to the same POA.

This is one of the serious headaches involved in regulating DBL rifles or smoothbores to put two balls or bullets to the same POA. A lot of people who have tried to do this, and finally succeeded, have sworn they will never do it again! :shocked2:

We now have laser bore sighting equipment that doesn't cost an arm and a leg, and I can't imagine trying to regulate 2 barrels, for either shot patterns, or for PRBs, without using this.
But, no matter what the bore alignment gauges can tell you, only actually test firing can tell you where the POI will actually be.

In your situation, I suppose you might try coning the mouth of the barrels on the INSIDE edge of both barrels, where they are joined, in hopes that the escaping gas at the crown would force the two balls to fly away from each other.

I saw a DBL shotgun at Friendship in a "used gun" rack, that had the bridge between the two barrels filed down SUBSTANTIALLY, done years before, based on the amount of patina and rust on the barrels. That could only have been done by someone who was trying to regulate the POI of the two barrels, After the rib had been solder in place, And he found that the patterns either crossed, or hit together at too close a range. This was a heavy gun, with 10 gauge barrels, that were 34-36 inches long. It would have been used for hunting waterfowl from a blind, rather than dragged out into the field to shoot flushing upland game birds. If you looked down at the muzzles from above the front sight, the mouth of the two barrels formed a substantial " U " shape. I have never seen another DBL shotgun with the muzzles filed down to that extent.

 

[Zonie]

Your experiment seems to bare out what I have always believed.

The axis of the bore in the last several inches before the muzzle determines where the projectile will fly, not the angle of the face of the muzzle.

I'm speaking of fairly moderate angles on the face of the muzzle here.

Taken to the extreme, if the muzzle was cut at something like 30-50 degrees to the bore, perhaps the gas pressures differential across the bore could deflect a roundball as it leaves the barrel but slight changes shouldn't have a great effect.

 

[CoyoteJoe]

I'm probably mistaken but from the photo it appears you are doing two contradictory things here. It looks like you've removed material from inside the muzzle at about 7:00 O'clock and from the whole muzzle end at about 2:00 O'clock. Correct me if I'm wrong but it seems those two actions would offset each other.

 

[Bearbait2]

Mr. CoyoteJoe,
Unfortunate optical illusion due to lighting. Metal has actually been removed from 9 o'clock and 12 o'clock. Additionally, at the start of the experiment, metal was only removed from the 9 o'clock position.
Sorry for the confusion.
Best Wishes

 

[Joel/Calgary]

Mr. WindWalker, did you try filing on the face of the muzzle before you filed on the inside? For those unfamiliar with this, when you do it, you file on the side OPPOSITE the direction you want to move the POI. This is supposed to work for both shot and ball. One often sees old shotguns with distinct angles to the muzzles from this form of regulation.

Regards,
Joel

 

[Bearbait2]

Mr. Joel/Calgary,
Yes.
Didn't work for us.