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I disagre the convergence should be a factor of recoil, elapsed barrel time and weight of the gun.
But you are right that its for the initial assembly. The finetuning could only be made on the range with a torch. But it wouldt take many rifles to see a pattern of convergence.
And if i was used to build doubles and had done so for 150 years i wouldnt need the use for a convergence table either.

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450_366, and Gentlemen, all regulators at all factories make a primary convergence, by educated guess. This, however, only a starting point, and will most times require several adjustments before the rifle is regulated.

When locking a set of double rifle barrels ( that are already regulated)into a vice with the sights lined up on a target at the distance engraved on the rear sight, what you will see is this!

The right barrel will be pointing to a point that is LOW, and on the LEFT of the POA of the sights, and the LEFT barrel will be looking at a point that is LOW, and on the RIGHT, of POA of the sights. To do this best is to chamber two empty cases, with no primers, and look through the primer hole down the barrel at the target but I suppose you could use a laser bore sighter, but it isn't needed for demonstration. This is because when the right barrel is fired, it rises UP and to the RIGHT. Also when the rifle's LEFT barrel is fired that barrel rises UP, and LEFT. When the convergence is right, the barrel being fired, will be pointing at the same place where the sights were pointing when the trigger was pulled. This is called barrel time. The barrels must be converging, because if they were parallel they would shoot high and wide.

Most folks are confused by this because there are two things that are called regulation, by the makers! ONE is the barrel's needed convergence, and the sights to point to the middle of the composite group of both barrels, and is simply the final adjustment of the iron sights.

Because the sights are REGULATED to a certain distance, it is assumed, by the un-schooled, that the shots cross at that distance, and this is not true. When a rifle is properly regulated, the center of each barrel's individual group is on it's own side of that composite group, and the sights are set half way between these two centers. The right side of the left barrel group, and the left side of the right barrel's group over lap giving you a slightly egg shaped composite group of both barrels, at the elevation marked on the iron sight being used.

The shots in a properly regulated barrel set, and with a proper load, do not cross at any distance, but shoot parallel regardless of distance.

If you tie a double rifle down so it cannot move, with the sights on the point of aim on a target at the distance engraved on the sight, the bullet from the right barrel will hit low, and left, and the left barrel will hit low, and right. This is because the recoil arch has been locked down so the rifle cannot move as the bullet travels down the bore to let the barrels point at the target on the POA when the bullet exits!

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..........Mac >>>===(x)===>
DUGABOY1, and MacD37 founding member of DRSS www.doublerifleshooterssociety.com
"If I die today, I have had a life well spent, for I've been to see the Elephant, and smelled the smoke of Africa!"

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