doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Double Gun Convergence question.

Franchi:

While I have had no issues with the generals with whom I have served, having found them to a man to be bright, honorable and conscientious, MG Hatcher's rank is completely irrelevant. He was a competent ballistician and engineer. I think Miller said it pretty succinctly , but there is an even better reason - the basic laws of physics require it to be so.

We have discussed this at length recently on the thread about calculating recoil on a 16g.

A gun recoils according to Newtons laws of motion. "For every action there is an equal and opposite reaction".

This expressed by the equation M1V1 = M2V2.

Your expert who said "no movement" has forgotten, or perhaps never learned, simple physics, and his whole statement can be carted off and used to encourage the cultivation of roses.

As for Winchester's pictures - the info did NOT come from their engineering department. It likely came from their marketing department.

Regards

GKT

The analogy that comes to mind is the one that Mohammad Ali used to say he was so fast he could flip the light switch off in a room and be tucked in bed before the room got dark.

"Theory"? Unbelievable! Hatcher wasn't espousing a theory, he was simply quoting the laws of physics, and proof abounds!

Chuck's explanation is exactly correct, and the double barreled gun itself is proof of it, although the double rifle is a better example than the shotty, because the regulation must be so much more precise. If Hatcher's "theory" was bunkum, it would be a simple matter to make an accurate double rifle - just set the barrels up perfectly parallel and it would shoot great. It doesn't work. If it did, double rifles would be much more common than they are, and a lot cheaper.

The barrels are in movement the entire time that the bullet is traversing the bore (called "barrel time"), and the recoil arc of the right barrel during barrel time isn't the same as that of the left. Worse, the arcs are not exactly opposite. The result is that the barrels are parallel in neither plane - they converge in the horizontal plane and diverge in the vertical plane - and well regulated DRs are capable of very small composite groups. They're regulated for a given bullet weight and velocity. Generally speaking, at a materially lower velocity, the barrels will shoot wide because barrel time is too long (the bullet is staying in the barrel too long during recoil movement). At a materially higher velocity they cross-fire, because barrel time is too short. It's the same with a double shotgun, but the degree of "regulation" tweaking required isn't as great.

It's just basic physics. Just get yourself a large bore double rifle, a handloading set up, and a chronograph and you can prove it to yourself.