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Old November 28, 2012, 10:58 AM   #10
Slamfire
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Join Date: May 27, 2007
Posts: 4,133
Quote:
Got to thinking this out a day or so ago. I dawned on me that while I've often stated that an out of square receiver face relative to the chamber axis makes a high point on it the hard spot on the barrel's tenon shoulder. Pressure builds there as the barrel heats up and expands.

But what if the bore's not perfectly centered on a barrel that's perfectly fitted to a squared up receiver face? The heated up metal on its thick side's gonna expand more than the thin side. It'll bow around its thin side. And that'll make the muzzle axis move away from where it was when the barrel was at ambient temperature.

There are ways to find out if a barrel's thicker on one side of the bore than the other; spin it on perfect centers in a lathe and put a dial indicator on its mid point. Any wobble on the dial might be indicating out of balance.

Thoughts, comments and things I might not think about are welcomed.
I found from gunsmiths and barrel makers that the gun drilled hole wanders inside the tube. Also, the exit hole and entrance hole are always offset. I was told by a barrel maker how he sorts barrels in categories of “hunters” and “target” by spinning drilled blanks between centers and observing the wobble.

A gunsmith told me of a mutual acquaintance who had bought a Krieger barrel. The barrel was installed correctly but shot so far left that it ate up all the windage on the gentleman’s sight. Another barrel was installed. The gunsmith marked the take off barrel, rethreaded and rechambered it so the left offset was pointed 90 degrees up. That barrel was installed on a palma rifle and shot great at 1000 yards. I think it was shooting high but at that distance, it just took less elevation.

Maybe someone with a CAD model could see how vibrations and frequency modes change based on bore alignment, but given the variation in barrels, barrel stresses, manufacturing, I don’t believe that we can give a definitive answer in the real world.
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