11-09-2014, 05:47 PM
Bob Prudhomme Wrote:John Lewis Wrote:Bob Prudhomme Wrote:John Lewis Wrote:Yes, it was mentioned further up the thread before I got involved.
This is not 'proof' that the particular rifle is behaving like it is purely due to the size of the bullet. The bullet design used by PPU is very different to the one used in Italian service ammo and it is a different weight. The bearing surface of their 139grn bullet is much shorter than that of the 160grn bullet which was alleged to have been fired from Oswalds rifle. The 6.5x52 (Carcano round) and 6.5x54 (Mannlicher-Schoenauer round) rounds use a very long, blunt nosed bullet, a type which PPU do not make. They simply use the same bullet they put in their 6.5x55 Swedish ammo as it's what they have on hand.
The Carcano rifle utilises a very fast rifling twist, as does the 6.5x54 M/S round, which is needed to stabilise the very long 160grn bullets. PPU 139grn ammo has a muzzle velocity of 2,500fps, that is at least 300fps faster than the ammo it was intended for with it's heavier bullet. The PPU bullet has a much smaller bearing surface (the bit which engages the rifling) so has a much greater chance of not engaging it at all. In addition, that bullet is small even by modern standards.
What I think is happening is probably this; the bullet has further to travel before it hits the rifling because it is shorter and its bearing surface is significantly further away from the throat. By the time it comes into contact with the rifling it is already traveling at a significant velocity because of its further travel. Because of its velocity, the fact that it is small even by modern standards (.2635") and that it has a small bearing surface it cannot grip the rifling and the rifling simply shaves off jacket material rather than allowing the jacket to be engraved. This means that the bullet is not being spun and so cannot be accurate.
I would put fair money on that particular bullet being perfectly accurate in that rifle if it were loaded into ammo with a lower muzzle velocity. That way it is exposed to far less stress when it engages the rifling and would have a much better chance of engraving it properly.
It would be interesting to see whther their load using a heavier bullet of 156grn, which I'm sure will be the same diameter, is accurate in this chaps rifle.
JL.
And yet, Prvi Partizan bullets are recovered, after being fired from a Carcano rifle, that show nicely engraved rifling marks on the bullet. According to you, that is evidence the bullet was spun and the jacket not just "shaved off" (what a silly notion).
What is your source for that information? The chap who wrote the article makes no mention of that.
Have you ordered any Hornady bullets yet so that you can measure them?
Have you accepted the fact, the legally mandated fact, that 6.5x54mm MS rifles do indeed have a groove diameter well in excess of .264"? You did, after call, call me a liar when I said (repeatedly) that my rifle had a .268" groove diameter.
JL.
Walks like a troll, talks like a troll, must be a.........
This exchange is over. I do not wish to give disinformation a platform to work from.
So that's your answer? You refuse to address any point I put to you, other than with some pitiable sarcasm and calling me a liar, and inventing some juvenile and barely rational retort about me being here to in some way attack you and spread 'disinformation'.
You speak of 'disinformation', by which I assume you mean that I'm here to undermine what you are saying by spreading lies? Well, have you bothered to have a look at your self and consider how you come over to anyone else reading this thread?
Consider this. I came here to post a simple critique and discuss some of the points you had made about a relatively obscure area of ballistics. To add to the mix my practical experience of having played around with firearms personally and professionally for thirty odd years, if you will. Almost every post you have made in response to mine has been, dismissive, sarcastic, down right offensive or a mixture of all of the above. I have even provided an independent, internationally legally binding set of specifications in response to your explicit allegations that I was lying which you still refuse to accept prove you wrong.
So, who has done you and whatever cause you seek to promote the most harm? Me and my alleged 'disinfo' or you and your utterly childish and petulant responses and seemingly tenuous grasp of reality? What do you think that any open minded, critically thinking person who had no pervious experience of the theory you are trying to advance would make of the exchange between the two of us? I think that many people would think that you were actually the one who was out to damage the cause, not me. Responses like yours harms everyone who shares your beliefs by association.
JL.