Carcano Rifles

[Bob Prudhomme]

From "Shooting the 6.5x52mm, 7.35x51mm Cartridges and the Carcano Rifles" by Dave Emary:

CARCANO RIFLES:
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I will not attempt to make any detailed discussion of the many varieties of Carcano rifles. For those interested in that I will refer them to Richard Hobbs' excellent book "The Carcano, Italy's Military Rifle". I will discuss some specific characteristics of the Carcano design in general and show how out of ignorance some of these have led to much of the bad press this rifle has received.
To begin this discussion the caliber of a rifle refers to the diameter of the bore of the barrel, or the diameter across the lands of the rifling. In the case of the Carcano rifles and for that matter every other 6.50mm caliber rifle this dimension is generally accepted as .257". The CIP minimum specification diameter for the 6.5 mm Carcano barrel is .256 in / 6.50mm. The groove diameter of the barrel is where a considerable amount of ignorance arises in the Carcano rifle. Nearly every other 6.5mm caliber has a groove diameter of .263 - .264". The exceptions to this are the 6.5 X 54 MS with a .266" groove and the Carcano with a CIP minimum specification groove diameter of .2677" / 6.80mm. I do not know what the production tolerances were for the Carcano, but based on my knowledge of current rifle manufacturing practice a tolerance of at least +.001" would be used for these dimensions. I have slugged the barrels of approximately 20 different types of Carcano rifles from 3 different manufacturers and have found barrel diameters in good condition rifles typically running from .2680" to .2690". I have a 91-24 that has a groove diameter of .2710". This rifle still has strong rifling and a somewhat shiny bore, but has seen a lot of use. Until very recently this bit of information has totally escaped the shooting sports industry. No bullets of the correct size were available, with the exception of only a few small bullet makers. This problem almost entirely has resulted in the Carcano being categorically called an inaccurate, poorly manufactured rifle. In fact noting could be further from the truth. 6.5 Carcano owners now have available to them as of the summer of 2002 an excellent .2675" 160 round nose bullet specifically designed for the 6.5 Carcano. This bullet is being offered by Hornady Manufacturing. The bullet is also being offered in ammunition loaded by Hornady for Graf & Sons.

[Bob Prudhomme]

In the late 1800's, European gunmakers began the transition from large bore, low velocity rifles shooting un-jacketed lead bullets with black powder to small bore, high velocity rifles that used smokeless powder. As the un-jacketed lead bullets quickly fouled the riflings of the smaller bores, the copper alloy bullet jacket was introduced to avoid this.

As a hold over from the black powder days, and even further back to the muzzle loaded Minie ball (see diagram),



the groove diameter of rifles was made slightly larger than the bullet itself. As the base of the Minie ball was conical, pressure from burning gases caused the diameter of the bullet to "slug up" to the diameter of the rifling grooves, making a tight fit and guaranteeing greater accuracy.

The original European bullet jackets in the 1890's and 1900's were much lighter than the later bullet jackets, making them pliable enough to allow them to swell under pressure to fill up the rifling grooves of early 20th Century rifles. As a consequence, CIP tolerances for the Mannlicher-Schoenauer groove diameters were, in the early 1900's, a few thousandths of an inch greater than the bullet diameters. I was unaware these tolerances were still on the books, as today's thicker jacketed (and harder) are definitely not likely to swell up to a larger diameter, and no manufacturer is making rifles with over sized rifling grooves.

Just because the CIP tolerances allow a manufacturer to make a groove diameter a great deal larger than the bullet diameter, does not mean they will actually do this. Mr. Emary found the 20 Carcanos he slugged to all be within .2680"and .2690"; just right for a bullet .268" in diameter (.2677" actually). Many gunsmiths have slugged Carcano barrels and found almost identical results as Mr. Emary. This fact alone is amazing, considering the conditions many of these rifles would have been made under during WWII.

The only exception Mr. Emary found was an M91/24 carbine which slugged out at .2710". As the M91/24 was the unfortunate carbine made by cutting down the 31 inch barrel of a worn out M91 long rifle to 17 inches, the large groove diameter is understandable, as the barrel has obviously been heavily worn by the tremendous number of bullets fired through it, as well as the corrosive nature of the early types of smokeless powder employed.

P.S. If you read some of my early threads closely enough, you will find that I pointed out, on several occasions, that the Carcano was not the only 6.5mm calibre rifle to shoot a uniquely oversized bullet. I have pointed out, on several occasions, that a bullet .266" in diameter is often used in the Mannlicher-Schoenauer instead of a standard .264" bullet. I stopped mentioning this fact simply because people were having enough trouble understanding what I was saying about the Carcano, without complicating the issue by adding more numbers. However, the Carcano, with its required .268" bullet, and the M-S, are the only exceptions to the 6.5mm rifles shooting a .264" bullet.

[Bob Prudhomme]

I hope this clears up any misunderstanding about Carcano and Mannlicher-Schoenauer rifles, and I apologize for not telling the forum about the uniqueness of the 6.5 Mannlicher-Schoenauer rifle with its .266" groove diameter; almost as unique as the Carcano with its .268" groove diameter. As I said, I felt there was enough data for you to digest without bringing a third rifle into the discussion.

[Bob Prudhomme]

Before anyone questions the credentials of the person I quoted in the first post, it should be known that the author, Dave Emary, is the chief ballistics scientist at Hornady Mfg.; a major American sporting ammunition manufacturer and the first company to produce the correct .268" diameter bullets post WWII for the Carcano rifles.

Mr. Emary plainly believes the accuracy of Carcano rifles suffered shooting .264" diameter bullets, such as those made by the Western Cartridge Co., and that this situation was not rectified until Hornady began making the correct .268" diameter bullets for the Carcano in 2002.

[Bob Prudhomme]

The argument is being made, of course, that Mr. Emary was only trying to promote .268" diameter bullets for the Carcano, and criticizing all other bullet makers for supplying .264" bullets for the Carcano, merely as part of the Hornady Mfg. sales pitch.

Here is a good question, then. What size of bullets do you think Hornady was making for the 6.5mm Carcano for decades, right up until 2002? If you said .264" diameter bullets, you win a cookie.

[Bob Prudhomme]

Bump

[Albert Doyle]

While visiting a friend he told me of an interesting purchase he had made. I immediately asked to take a picture and handle it. Nice little piece of history. (Side mount model)

[Bob Prudhomme]

Is there an "SA" inside of a little square, stamped on the base of the barrel?

[Albert Doyle]

Is there an "SA" inside of a little square, stamped on the base of the barrel?

I distinctly remember seeing a square with something in it stamped on the barrel. I'll call him and get him to check.


The iron sights gave a good bead. I was impressed how easily I could true the triangle sight with the notch sight.


There's no way in hell Oswald made those shots with that clunky hunk of iron.


Edit: Bob - The Finland SA squares shown on Google images is not what I saw. I saw a sharper, larger square centered on the barrel. More like the above if I recall correctly.



.

[Albert Doyle]

Bob:


Per my friend:


The barrel contains stamps indicating XVIII - Made Italy 1940 - Beretta - Gardon


Serial Number: UC1882

Caliber: 6.5


He says there's an indistinct oval stamp with a crown and something that has been rubbed out.