Double Barrel Muzzle Question

[KLMoors]

Hi Folks.

I am finishing up a double barrel flintlock shotgun. The barrels for this gun were New Old Stock barrels and had never been cleaned up or chambered. They are not Damascus. The muzzles are both a little out of square, in multiple directions, but I figured I would pattern the gun before doing any filing.

I took it out and patterned it last weekend.  I noticed that the left barrel is shooting about 3 or 4 inches to the left at 20 yards.    The left hand barrel (the one shooting to the left), is a little longer on the outboard side, maybe 1/32 of an inch or so.  As I understand it, this should move the pattern to the right. I would like to get it shooting to point of aim.

Now, since these barrels had never been chambered, is it possible that they were tested for regulation somehow and filed this way on purpose? I have no idea how they could have done that with unchambered barrels.  Again, both muzzles are a little crooked, so if they were filed, they weren't done very carefully.

My inclination is to file them square, and then go from there, depending on the results.

By the way, the gun shoulders real well for me and I am looking straight down the center of the rib, so I don't think it is a stock fitting problem.

Any thoughts on how to proceed?

[kutter]

I'd square them up and start from there.
Uneven muzzle ends isn't going to reflect well on craftsmanship and you'll be chasing the patterns around and around trying to center them if you attempt to use them as a directional deflector.

Assuming there are factory chokes in the new-old-stock (cartridge) bbls,,you can better deflect the patterns by altering the choke to one side or the other than the uneven mouth of the bbl.

Careful honing a few .000" at a time from one side will deflect the pattern to that side. It's slow work and you need to test often. Different loads will pattern differently too just as with any shotgun but it can be done.

Most all cartidge bbls are/were simply put together on a jig after the breech end was brazed together. The muzzles were leveled and brought together to touch (in most instances) and 3 or 4 spacers are soft soldered inbtw the tubes.
Then the ribs are soft soldered in place.
The jig set up was built to bring the bbl's to a converging pattern after some experimentation, but there wasn't any hand wringing and worrying over it beyond that. Once together, that was it unless a set was shown to really throw wild pattern centers in a test firing.

Most do not shoot both bbls to POAim at 30yrds. If they print within 6in+ of that, they are doing good.
It is a shotgun afterall.
Double Rifles are another story and that's where the hard regulation comes into play. Individual loads are also part of the equation  here just as they can be with a shotgun pattern.

[D. Taylor Sapergia]

I have seen muzzle loading shotguns with muzzles apparently filed out of square.  But if you want the pattern to move to the right from the left barrel, I'd suggest you file more from the left side.  As the shot column is exiting the bore, the powder gases will blow out of the left side first relatively speaking, and tip the shot column to the right.  But start with the muzzles square to begin with, and then experiment.

[KLMoors]

Thanks guys. That was my inclination too. But I figured I'd better ask, since I'd never worked on this issue before.  Thanks again.

[Captchee]

I have seen muzzle loading shotguns with muzzles apparently filed out of square.  But if you want the pattern to move to the right from the left barrel, I'd suggest you file more from the left side.  As the shot column is exiting the bore, the powder gases will blow out of the left side first relatively speaking, and tip the shot column to the rifle. 

  yep i seem to recall reading that as well . the other was  small dent on the crown  of  the afflicting barrel  the muzzle .

[Dphariss]

John Baird wrote that it was likely to keep round balls from crossing. The degree he saw on old shotguns would likely have blown the pattern. But I don't think anyone knows the REAL reason. But Baird's idea is as good as any.

Dan

[kutter]

I have seen muzzle loading shotguns with muzzles apparently filed out of square.  But if you want the pattern to move to the right from the left barrel, I'd suggest you file more from the left side.  As the shot column is exiting the bore, the powder gases will blow out of the left side first relatively speaking, and tip the shot column to the rifle. 

  yep i seem to recall reading that as well . the other was  small dent on the crown  of  the afflicting barrel  the muzzle .

If you're going with the uneven muzzles,,do as above.
I was relating how to alter the shot pattern POImpact by working on the inside of the bore at the muzzle.
It's quite like putting a jug choke into the bbl but you just put it in a portion of the bbl wall and feather it out to the original wall around it. The alteration goes in the position you want the shot pattern direction to move.  .002/3" is generally deep enough.
Yes it's more work.

[Daryl]

John Baird wrote that it was likely to keep round balls from crossing. The degree he saw on old shotguns would likely have blown the pattern. But I don't think anyone knows the REAL reason. But Baird's idea is as good as any.

Dan

Many of the side by side or 'double" rifles (round ball guns) made in the States, it seems, Colt, for instance, had the muzzles filed, seemingly to direct a round ball or bullet's flight, as Dan noted J. Baird's opinion above. This was much more easily accomplished and was very much cheaper than the normal higher quality English method' of painstakingly 'regulating' the barrels to a given load, by soldering, shooting, separating, wedging re-soldering, shooting, etc until the barrels shot with perfect regulation.

There is a modern double rifle maker - Sabata, I think (sounds right), who was also doing this - filing the muzzles to direct the bullets to regulation for a given load. They have stopped this practice and have gone to the English method noted above for their regulation due somewhat to the negative press they received from the double-gun forums.

The company was severely chastised for this cost cutting, and ugly method of regulation. Not only were the muzzles filed off 'square' but they also had the muzzle's crowned crookedly in an attempt to further direct the powder gasses effect on the bullet's base. They were quite effectively the most ugly muzzles ever, appearing to be sloppy workmanship - even though they achieved the goal of reasonable regulation.

Pretty sure John had this theory nailed in fact.  It was not merely idle speculation.  That the modern double gun maker also used this method, lends truth to John's idea, if not Colt's methods.

[kutter]

The Sabbati DR (Model 92 IIRC) is a production rifle that has it's bbls set up for convergence and POI on a jig and are assembled in a factory.
 Sabbati calls it a state of the art assembly method that does away with the time consuming and expensive method of regulating a DR that has been the norm in the industry in the past.
They had to come up with something to be able to sell the rifle in the price range they are offered in.

Muzzles are not filed at an angle to further regulate the shots to target. They are square to the bore.
Most perform within reasonable expectations of their owners. Not being target rifles or long range pieces, being able to dump 4 shots, 2 from each bbl into a dinner plate at 50m seems to satisfy most fair-weather weekend safari shooters.

What Sabbati did do on a more than few of the rifles to further regulate some of the 'problem children' of the group was to grind the lands off of the bore just inside the muzzle for a depth of about 1/2 to 3/4 inch.
This was done free hand it looks like with a small bit on a flex shaft most likely.
The goal was to allow the escaping gases to coax the bullet to fly to the direction needed to tighten up the group.

Owners/buyers were furious a the sloppy craftsmanship and immediately demanded replacement bbls, complete rifles, or their $$ back on the purchase all together,

Ground off rifling, oval and crooked muzzles aren't popular with customers

[T*O*F]

I don't know why they can't put lasers in each barrel during regulation.  At least that would get them pointing where they want at some predetermined distance.  Not unlike the method used for bore sighting a scope.

[kutter]

It's not as simple as a bore sighting on a DR as it is on a single bbl. The twisting effect of the recoil & off center bbl  from the line of sight and all that happening before the bullet exits the bore makes for quite an art to get one regulated to shoot small groups  w/a desired load,,each bbl on top of the other.

A laser bore site on an already regulated  DR may show the bores printing way low & out to the left and right ,,,by the right and left bbls respectively .
But a heavy caliber may require that as the recoil and twisting of the gun during firing brings the rifle up to the desired POI at the moment the bullet(s) exit the bore. 
Change the load, bullet weight, ect and most often the impact changes again for no other reason than recoil and load velocity (time in bbl).

That can be useful in regulation sometimes if a load within the accepted range is found to work with the bullet weight the customer wants to use.
Each is a law by itself. Some will regulate very easily and print various loads with acceptable results. Others will resist most everything & trick you try.

When regulating by the standard method of loosening the solder joint and moving the bbls up/down or spreading them apart at the muzzle to group the shots,,the adjustments made are on the order of  a few .000" movement to move POI at 50m

[Daryl]

I stand corrected - NP - the picture I saw looked like the muzzles were crooked, but perhaps it was the crowns only - they were really wonky.

[jerrywh]

 This proves the point that if you think something is simple you just don't know much about it.

[SuperCracker]

I believe Sabatti has since apologized for the grinding of the lands and now actually regulates the rifles in the conventional manner, but perhaps not to the finicky degree of high en DR builders. There were some who got good deals on the ground muzzle guns, trimmed and recrowned barrels and the regulated them properly and ended up with decent rifles.

[KLMoors]

Interesting stuff you guys. I was wondering the same as TOF. Too bad that idea won't do it. It seems like a laser would be the perfect tool for something like this. No wonder those double guns cost so much.