17-04-2014, 06:27 PM
[quote=Drew Phipps]
Do you have any figures for the weight loss that occurs when the Carcano bullet with the thicker jacket is fired thru the MC 91/38? (Harold Wiesberg estimated that weight at half a grain.) You would suspect that a rifle with deep grooves would inflict a higher weight loss on the bullet as it carves out the rifling marks on the bullet than a rifle with shallower grooves. I don't recall anyone but Howard Wiesberg (a fair bit of time ago) adding in this "end-of-barrel" weight loss with the bullet fragments recovered from Connally to determine if CE 399, the magic bullet, was of the proper weight to have left all those fragments. Half a grain seems pretty significant to me. [END QUOTE]
I'm not really sure, outside of microscopic traces, if bullets jacketed in copper alloys actually leave much in the way of metal depositions in the rifling grooves of a barrel. Bullet jackets were first developed, after all, to solve the problem of unjacketed lead bullets depositing great amounts of lead in the riflings. Half of a grain certainly sounds like an excessive amount, although Weisberg is a scientist and he may know more than I do. However, if each shot deposited half of a grain of metal, it would not take many shots to completely throw the accuracy of the rifle off.
At the throat of a rifle barrel, where the bullet begins its journey, the raised "lands" that actually make the impression seen in a spent bullet do not begin with an abrupt shoulder but, rather, begin gradually; allowing the lands to slowly work their way into the malleable copper alloy without tearing metal away. The tapered nose of a pointed (or round) bullet assists in getting the bullet started, too. If this were not true, each bullet would leave a great deposit of metal at the throat of the barrel. Once the bullet is fully engaged in the riflings, the land impressions are formed on the bullet, and the bullet then travels through the lands like a bolt being threaded through a nut.
P.S. The only exception to the above analogy are the other Carcanos with their "progressive" twist rifling, where the rate of twist begins at a gentle 1:20 or so, and eventually tightens to around 1:8. One would think that such a dramatic change in rate of twist would tend to tear the jacket up, yet the bullets fired from these rifles really don't look different from other spent bullets. Perhaps the copper alloy is malleable enough to allow it change shape as the rate of twist changes.
Do you have any figures for the weight loss that occurs when the Carcano bullet with the thicker jacket is fired thru the MC 91/38? (Harold Wiesberg estimated that weight at half a grain.) You would suspect that a rifle with deep grooves would inflict a higher weight loss on the bullet as it carves out the rifling marks on the bullet than a rifle with shallower grooves. I don't recall anyone but Howard Wiesberg (a fair bit of time ago) adding in this "end-of-barrel" weight loss with the bullet fragments recovered from Connally to determine if CE 399, the magic bullet, was of the proper weight to have left all those fragments. Half a grain seems pretty significant to me. [END QUOTE]
I'm not really sure, outside of microscopic traces, if bullets jacketed in copper alloys actually leave much in the way of metal depositions in the rifling grooves of a barrel. Bullet jackets were first developed, after all, to solve the problem of unjacketed lead bullets depositing great amounts of lead in the riflings. Half of a grain certainly sounds like an excessive amount, although Weisberg is a scientist and he may know more than I do. However, if each shot deposited half of a grain of metal, it would not take many shots to completely throw the accuracy of the rifle off.
At the throat of a rifle barrel, where the bullet begins its journey, the raised "lands" that actually make the impression seen in a spent bullet do not begin with an abrupt shoulder but, rather, begin gradually; allowing the lands to slowly work their way into the malleable copper alloy without tearing metal away. The tapered nose of a pointed (or round) bullet assists in getting the bullet started, too. If this were not true, each bullet would leave a great deposit of metal at the throat of the barrel. Once the bullet is fully engaged in the riflings, the land impressions are formed on the bullet, and the bullet then travels through the lands like a bolt being threaded through a nut.
P.S. The only exception to the above analogy are the other Carcanos with their "progressive" twist rifling, where the rate of twist begins at a gentle 1:20 or so, and eventually tightens to around 1:8. One would think that such a dramatic change in rate of twist would tend to tear the jacket up, yet the bullets fired from these rifles really don't look different from other spent bullets. Perhaps the copper alloy is malleable enough to allow it change shape as the rate of twist changes.
Mr. HILL. The right rear portion of his head was missing. It was lying in the rear seat of the car. His brain was exposed. There was blood and bits of brain all over the entire rear portion of the car. Mrs. Kennedy was completely covered with blood. There was so much blood you could not tell if there had been any other wound or not, except for the one large gaping wound in the right rear portion of the head.
Warren Commission testimony of Secret Service Agent Clinton J. Hill, 1964
Warren Commission testimony of Secret Service Agent Clinton J. Hill, 1964