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Old September 4, 2012, 07:25 AM   #26
Picher
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The exception to the rule that a little copper is good for a bore is when shooting Barnes all-copper bullets. Sometimes they foul barrels in 10-20 shots, not all barrels, but my .270 Win accumulated so much that pressure was raised and primers flattened, bolt opened harder, and velocity changed. (Coated TSXs may not foul, but I haven't tried them.)

It was also difficult to clean the bore. I could feel the roughness as I cleaned it and was concerned that it wouldn't come out, but it took many bronze brush strokes with solvent to get it clean. I now use Hornady GMX (Gilding Metal) bullets that work just as well as the Barnes TSX on game, but don't foul the bore.
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Old September 6, 2012, 06:43 PM   #27
ltc444
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Kraigway can probably correct me but, my recollection is that the old M-60 barrels could withstand 5minutes of sustained Continuous firing before the barrel started to droop.
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Old September 7, 2012, 12:40 PM   #28
Bart B.
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Barrel droop?

Reminds me of the old mechanical computers used on battleships and heavy cruisers that had compensating cams in them to correct for 8", 12" and 16" barrel "droop." Their muzzle axis was actually below the breech axis which is used in the primary elevation calculations for where to point the gun to hit the target. Barrel droop was greatest at zero elevation; got less as the gun elevation angle went up. Which is what the droop cam corrected for in changing the elevation gun orders just a smidge to correct for it.

Shoulder fired rifle barrels also droop from their own weight even while at ambient temperature. Put an optical collimator in the muzzle, zero the sights on the collimator with the barrel in the vertical, then lower it to the horizontal and watch the collimator reference go below the sight axis.
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Old September 7, 2012, 02:20 PM   #29
ltc444
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probably need to clarify. The barrel droop was caused by over heating the barrel to the point the metal lost its strength. In the "test" I saw the muzzle literally moved down about 2 inches.

My point is that I do not believe a bolt action rifle can be fired fast enough for a long enough time to damage the barrel do to overheating.

Last edited by ltc444; September 7, 2012 at 02:20 PM. Reason: admend
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Old September 7, 2012, 02:24 PM   #30
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I am more concerned with throat erosion than the barrel looking like a boiled noodle. A bold gun could not reach the heat that the M60 does, but I would be curious as to how many shots it would take till the throat is gone in the M60.
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Old September 7, 2012, 10:36 PM   #31
Bart B.
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Quote:
My point is that I do not believe a bolt action rifle can be fired fast enough for a long enough time to damage the barrel do to overheating.
I know of at least two instances when a new barrel was fit to a 30 caliber magnum 1000-yard match rifle and the owners thought they ought to be "broken in" with several shots. Both had several dozen shots fired 5 to 6 seconds apart.

Sighting them in at the range with scopes installed, neither shot under 2 MOA at 300 yards. Normal for such barrels and ammo was about 1/3 MOA. Bore erosion gauge inserted in their throats showed the same amount of wear as a .30-06 after about 6000 rounds. They were now not fit for competition.
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