10-09-2014, 12:00 AM
(This post was last modified: 10-09-2014, 12:20 AM by John Lewis.)
Bob Prudhomme Wrote:I have been expecting an attack of this type and, as usual, the qualifications of the author are easily discredited.
To quote "John Lewis":
"I own a Mannlicher-Schoanauer model 1903 carbine which uses an almost identical round. I have not slugged the barrel but it is factory marked as being 6.7mm which is a diameter of .2637". This is the bore diameter, not the grove diameter. As has been correctly pointed out, all current and past 6.5mm bullets, with the exception of the Carcano ones measure .264". Steyr, the maker of my rifle, knew this yet still produced rifles with a a bore diameter of only .003" smaller. I would guess that grove diameter of my rifle is at least .268. The author of the document linked to here has identified one rifle with a groove diameter of .269"! Remember, all the available ammo used .264" bullets."
If one goes to this conversion table site http://www.onlineconversion.com/length_common.htm and converts 6.5 mm to inches, one will get a figure of .2559" or .256". This is the actual bore diameter of a Carcano, Mannlicher-Schoenauer and any other 6.5mm calibre rifle, not .2637" as Mr. Lewis tells us. The figure of .2637" or .264" is the GROOVE diameter of the average 6.5mm rifle, as well as the diameter of the bullet.
The question of whether or not the standard diameter bullet for most 6.5mm calibre rifles, which is .264" in diameter, has been decided long ago. ALL Italian cartridges for the 6.5mm Carcano rifle were loaded with a bullet that was .268" in diameter. There are literally dozens of pages written by persons far more qualified than Mr. Lewis explaining how shooting .264" diameter bullets from a Carcano rifle will produce inaccurate shots. This is thje reason why Hornady, in 2004, finally came out with a .268" diameter specifically for Carcano rifles.
The idea that the Western Cartridge Co. 6.5mm Carcano bullets were loaded with .268" bullets pulled from Italian cartridges is utter nonsense. One only need look at this photo of CE 399, a WCC bullet.
The WCC bullet above has a "cannelure" near the base of the bullet. While some of the Italian military bullets also had cannelures, they were nowhere near as wide or distinctive as the WCC bullet.
Lastly, this is my favorite from Mr. Lewis:
"[size=12]To qualify all of that; yes, a bore which is larger than the bullet diameter, especially significantly so will have an effect on accuracy and can cause gas blow-by which also theoretically can have an effect. These are all very small matters though and the effect on shots taken at short range is insignificant. The problem of gas blow-by isn't really one of accuracy, it is one of barrel wear. Gas which is attempting to get through a very small gap as we are talking about here leads to localised very high pressures and temperatures which causes undue wear to the the bore."
A bore that is larger than the bullet diameter??? The bullet diameter and the groove diameter are the same. Look at this diagram and someone please tell me just what the hell Mr. Lewis is going on about.
P.S. The Hornady bullets for the 6.5mm Carcano are, indeed, .268" in diameter. Do not believe Mr. Lewis. He is spreading disinformation.
[/SIZE]
I have slugged the bore of my rifle and the groove diameter is .268", in fact it may actually be a touch larger. As stated in the link I posted - which was to an old issue of a Mannlicher collectors magazine - these rifles have been encountered with groove diameters of up to .269" and the larger sizes are quite usual. As we know, all 6.5mm bullets (bar the Italian military ones) are .264" diameter. Why then did Steyr-Mannlicher make rifles with such large groove diemeters if the result would be that they could not hit a target the width of the shoulders of a man at well under 100 yards.
My rifle is most certainly marked 6.7. Believe that or not if you so choose - I know it as a fact. Look here the first rifle (in 6.5x54) is marked 6.5. Your assertion that these marks relate to groove diameter cannot be correct because if so then this one must have a .256 groove diameter which simply cannot be true. It would have blown up during proof!
The assertion that all Italian 6.5 ammo was loaded with .268" bullets seems not to be true either. See post number 17 here. The chap says he has pulled original military surplus ammo and the bullets measured .266". Also, if you check post 7 on that thread you will see that it is by someone who actually owns some WCC ammo and has pulled one of the bullets. Guess what? They measure .266", not .264! This means that there are other 6.5mm bullets which aren't .264".
You are taking my comment about WCC ammo being loaded with pulled Italian bullets entirely out of context. I didn't state it as a fact. Look at the manner in which I wrote it; I was just putting it up for discussion as being something I had heard or read somewhere many years ago. I never said that it was true.
You are also incorrect about the Hornady bullets measuring .268". They don't and never did. Not even Hornady still call them .268" diameter any more. I have just re-measured the ones I have and they are .2665" as close as I can measure them. This is from an old type Hornady box rather than the new shiny one and the bullets are clearly not new and have been sitting on a shelf a while so it isn't the case that they have recently changed the dimensions.
Your last comment about my referencing bore/grove diameters is to miss the point somewhat. My use of the word 'bore' was nothing more than a touch of brain-fade on my part, it should have been 'groove' instead. Anyone reading the discussion in context can see that. The bottom line being that firing a .264" bullet through a barrel with a .268" groove diameter will not result in a catastrophic loss of accuracy as you are suggesting. It will be, and is, virtually insignificant. The bullet is engaged in the rifling and that is all that required. I know because I have done it and do it all the time. It is fairly easy to knock down man-sized targets at 250'ish yards from a standing position using the rifle's open sights. I was doing just that only a few months ago when I last shot the rifle.
I have to say that your response has somewhat stunned me. All I came here to do was discuss a particular firearms related subject which interested me and which I have a bit of knowledge about. The very first reply I got started out with accusations of me staging an 'attack' on you by simply daring to take issue with something that you had said. You then proceed to set up some straw-man argument when you attempted to undermine and 'discredit' my 'qualifications'. I haven't referred to any 'qualification' I may or may not hold. I'm not pretending to be anyone I'm not and, quite honestly, the whole discussion of how JFK actually met his end and by whom is fairly unimportant to me in the great scheme of things. I don't particularly care one way or another. It's an interesting topic of conversation and not a lot more. The part that interests me is the firearms side and not much else.
You state a lot of things as being fact here. So, to ask:
Have you personally measured the bullets from any WCC 6.5x52mm Carcano ammo?
Have you personally measured any Hornady 6.5mm Carcano bullets code number 2645? This is an easy one to do as any decent gun shop will be able to order them for you.
Have you personally measured the groove diameter of a Mannlicher-Schoenauer 1903 rifle by slugging the bore?
Have you personally tested the accuracy of an Italian 6.5x52mm Carcano rifle with either Italian service ammunition and reloads or modern ammo using .264" bullets?
JL.