Mark Knight Posted February 3, 2015 Share Posted February 3, 2015 Perhaps they had "heard" of the .257 Roberts...and wanted to sound educated? Link to comment Share on other sites More sharing options...
Robert Prudhomme Posted February 3, 2015 Author Share Posted February 3, 2015 (edited) Hi Jon A rifle is usually cleaned before a sulphur cast is made, as one of the reasons for making a sulphur cast, beside determining calibre and model, is to determine the condition of the throat and the lands and grooves, and removing any build up will give you a clearer picture. A sulphur cast is easy to make, and is most often made of the chamber end of the barrel. The bolt is removed, the barrel cleaned and a light coat of oil is applied to the inside of the barrel with a patch. The oil facilitates easy removal of the sulphur cast once it cools. The rifle is then clamped in a vertical position with the muzzle down. A plug, made from another patch or even a wad of paper towel, is pushed down the barrel, from the chamber end, to a point about an inch past where the riflings begin. Sulphur is gently melted in a small pot with a spout and, when liquefied, gently poured into the chamber until it has filled up to where the face of the bolt would be when closed. Once the cast has cooled and solidified, it is possible, often, to push it out of the chamber by inserting a long wooden dowel from the muzzle end. At most, a couple of taps on the dowel from a mallet should be enough to dislodge it. Once removed, you will have a perfect 3-D model of your rifle's chamber and the first inch or so of the barrel. Now, it is perfectly possible the barrel of C2766 was corroded, but this does not mean that it had to be rusty, as well. I have seen very clean rifle barrels showing the evidence of severe corrosion. www.youtube.com/watch?v=j8jE2o7ePbo Edited February 3, 2015 by Robert Prudhomme Link to comment Share on other sites More sharing options...
Robert Prudhomme Posted February 3, 2015 Author Share Posted February 3, 2015 LOL Mark. There you go, the typical North American rifle designations that confuse everyone, including our experts at the FBI. It's confusing, for the novice, to understand that the .250 Savage and the .257 Roberts both shoot a bullet .257" in diameter. Same goes for the 30-06 and the .308 Winchester, both shooting a .30 calibre bullet that is .308" in diameter. Link to comment Share on other sites More sharing options...
Ian Lloyd Posted February 3, 2015 Share Posted February 3, 2015 Hi Robert, When removing the cast, if it has set within a portion of the barrel that contains the rifling, would the cast have to be rotated as it's being removed to maintain the profile of the lands & grooves (akin to being threaded back out)? You say that it appears to have been cast at the muzzle end of the barrel - this would therefore include rifling along the entire length of the cast? If there is progressive/gain twist in this particular barrel, it seems to me that it would be difficult to remove maintaining the profile accurately intact. I notice that The WCR states that a micrometer was used to measure the caliber of the rifle which is between opposite lands. When a sulfur cast is made, it will be the equivalent of a photographic negative of the inside of the barrel so the caliber would have to be measured in the grooves of the cast? Link to comment Share on other sites More sharing options...
Robert Prudhomme Posted February 3, 2015 Author Share Posted February 3, 2015 (edited) Hi Ian Very good questions. I have only ever seen sulphur casts made from the chamber end of a barrel, and cannot understand why Frazier would make a sulphur cast from the muzzle end, as the dimensions of the chamber (and thus the cartridge) are very useful in establishing the make of a rifle. Just knowing the rifle is a 6.5mm calibre is not always enough, as there are several European rifles with this calibre. If you watched the Youtube video I posted, you'll see the gunsmith had no trouble removing his cast, with the small amount of riflings on it, and it did not seem to break any part of the brittle sulphur. I think this is accomplished by the sulphur shrinking a tiny bit, allowing the cast to turn in the riflings as it was pushed out. The same problem would be encountered in progressive twist rifling as in standard twist rifling, although it might be simpler to remove from the progressive twist barrel, as the rate of twist would be nowhere near as tight. I am unable to cut & paste on this site again but, Frazier's sulphur cast can be seen at the Mary Ferrel website. It is listed in evidence as CE 540. It is not a very good photo and it is hard to see the riflings very well on it. If you can find a way to enhance the photo, we are looking for a rate of twist of 1:8.47 to establish C2766 as an M91/38 with standard twist rifling. If the rate of twist is closer to 1:12, this could mean the barrel of C2766 is a cut down M91 long rifle barrel with progressive twist rifling. The land impressions on the cast would be too small too get a micrometer into. They would have miked the inside of the barrel to measure the lands. Edited February 3, 2015 by Robert Prudhomme Link to comment Share on other sites More sharing options...
Ian Lloyd Posted February 3, 2015 Share Posted February 3, 2015 Hi Robert, Thanks for that - a few clarifications required and comments: 1. If the sulphur cast was found to be "..shrinking a tiny bit...", given the dimensions we are talking about measuring (thousandths of an inch), a "tiny bit" could actually turn out to be significant? 2. "...although it might be simpler to remove from the progressive twist barrel, as the rate of twist would be nowhere near as tight." I'm not sure about that - I think of it as a thread, if I'm trying to remove the cast through a thread that constantly changes, I suspect that the profile will become damaged since the profile further inside the barrel will never match the profile as it approaches the end of the barrel. 3. Yes, I've seen the photograph - I think it is too poor to really deduce anything from it. 4. If the outermost diameter of the sulphur cast is measured, that would effectively be the barrel "groove diameter"? Link to comment Share on other sites More sharing options...
Ian Lloyd Posted February 3, 2015 Share Posted February 3, 2015 No one is saying an M91 Carcano was found in the TSBD. What I am saying is, after the rifle was identified as a Carcano, a hurried search was likely made for info on Carcano rifles. As the M91 long rifle was the main infantry weapon, and more of them were made than any other model of Carcano, the specs for it were what they probably found first. This source should be seen as suspect, not only because they were way off with the muzzle velocity of an M91, but because they stated, as you pointed out, the calibre as being between .270" and .280", much larger than the Carcano calibre of .256". I hate to say it but, the coincidence of the M91 Carcano and the Japanese Type "I" rifles both having identical barrel and overall lengths has started everyone on a wild goose chase that I do not believe will lead anywhere. Remember, the rifle was also identified early on as a Lee Enfield .303. Interesting stuff from Page 554 of the WCR: The rifle was identified as a 6.5-millimeter Mannlicher-Carcano Italian military rifle, Model 91/38. This identification was initially made by comparing the rifle with standard reference works and by the markings inscribed on the rifle. The caliber was independently determined by chambering a Mannlicher-Carcano 6.5 millimeter cartridge in the rifle for fit, and by making a sulfur cast of the inside of the rifle's barrel which was measured with a micrometer. (The caliber of a weapon is the diameter of the interior of the barrel, measured between opposite lands. The caliber of American weapons is expressed in inches; thus a .30-caliber weapon has a barrel which is thirty one-hundredths or three-tenths of an inch in diameter. The caliber of continental European weapons is measured in millimeters. A 6.5-millimeter caliber weapon corresponds to an American .257-caliber weapon, that is, its barrel diameter is about one-fourth inch.) The identification was later confirmed by a communication from SIFAR, the Italian Armed Forces Intelligence Service. This communication also explained the markings on the rifle, as follows: "CAL. 6.5" refers to the rifle's caliber; "MADE ITALY" refers to its origin, and was inscribed at the request of the American importer prior to shipment; "TERNI" means that the rifle was manufactured and tested by the Terni Army Plant of Terni, Italy; the number "C2766" is the serial number of the rifle, and the rifle in question is the only one of its type bearing that serial number; the numerals "1940" and "40" refer to the year of manufacture; and the other figures, numbers, and letters are principally inspector's, designer's, or manufacturer's marks. Are the measured dimensions of the sulfur cast available anywhere, I wonder? The caliber was independently determined by chambering a Mannlicher-Carcano 6.5 millimeter cartridge in the rifle for fit, and by making a sulfur cast of the inside of the rifle's barrel which was measured with a micrometer. It is not clear here as to what was actually measured, the sulphur cast or the inside of the rifle barrel - I can't imagine being able to get a micrometer inside the rifle barrel, so I suspect the cast was measured. If that is the case, then there is a problem... Link to comment Share on other sites More sharing options...
Mark Knight Posted February 3, 2015 Share Posted February 3, 2015 Traditionally, where a space is too small to measure with a micrometer, the distance/diameter/whatever is being measured is checked with a divider, and the distance transferred to the divider is then measured by micrometer. Margin for error? Some...usually miniscule, depending upon the skills of the person taking the measurement. Link to comment Share on other sites More sharing options...
Malcolm Ward Posted February 3, 2015 Share Posted February 3, 2015 You could use a vernier caliper.I have used them myself in the past when using lathes boring out metal.Example here. http://www.instructables.com/id/How-to-read-a-vernier-caliper/ Link to comment Share on other sites More sharing options...
Ian Lloyd Posted February 3, 2015 Share Posted February 3, 2015 I understand that a vernier calipers could have been used to measure the internal bore, but the point is that the WCR wording indicates to me that the outer diameter of the sulphur cast is what was measured with a micrometer. Link to comment Share on other sites More sharing options...
Chris Davidson Posted February 3, 2015 Share Posted February 3, 2015 LOL Chris, you must have really done some digging, in order to come up with the 6.5x50mm Carcano Type "I" made for the Japanese Navy. This was a fairly limited production model that very few people today have even heard of. As the article you linked to states, It was basically the standard Carcano receiver and bolt, mated to a barrel chambered for the Arisaka 6.5x50mm cartridge. Interestingly, the bullet loaded into this cartridge was almost identical to the Carcano bullet. Both weighed 160-162 grains, both were round nosed and both were virtually identical in length. The main difference was the Arisaka 6.5mm bullet was .264" in diameter, as were most 6.5mm bullets, while the Carcano bullet was .268" in diameter, although there is a great deal of evidence showing the 6.5mm Carcano cartridges made by the Western Cartridge Co. (Oswald's alleged cartridges) were loaded with bullets only .264" in diameter. While there were small differences, even the brass casings were very similar. Robert, Mr. FRAZIER - The overall length is 40.2 inches. It weighs 8 pounds even. Mr. McCLOY - With the scope? Mr. FRAZIER - Yes, with the scope. The CHAIRMAN - And the sling? Mr. FRAZIER - That is with the sling, yes, sir. The sling weighs 4 3/4 ounces. The stock length is 34.8 inches, which is the wooden portion from end to end with the butt plate attached. The barrel and action from the muzzle to the rear of the tang, which is this portion at the rearmost portion of the metal, is 28.9 inches. The barrel only is 21.18 inches. 30.75 inches - 21.18 inches = 9.57inches 40.2 inches + 9.57inches = 49.77inches http://candrsenal.com/rifle-carcano-type-i/ Were there other long rifles that started at 49.75 inches before the barrel was shortened? chris Link to comment Share on other sites More sharing options...
Chris Davidson Posted February 3, 2015 Share Posted February 3, 2015 Also, In regards to CE560: http://www37.zippyshare.com/v/9vl8z1DL/file.html The rest of the article on the Arisaka rifle is here, if interested. http://www.chuckhawks.com/arisaka_sporter.htm chris Link to comment Share on other sites More sharing options...
Robert Prudhomme Posted February 3, 2015 Author Share Posted February 3, 2015 Hi Ian 1. I became curious about this too, so I checked into it. The general consensus seems to be the cast will shrink by .002-.003", which could be a significant amount. It is said that adding powdered graphite to the molten sulphur will stop it from shrinking as it cools. 2. The change in the rate of twist is very gradual, and I doubt you would really notice much of a change in a one inch section of barrel. 3. Yes, it is a poor photo of CE 540. I'm hoping someone has a better photo or can enhance that one. 4. That's right, the outermost diameter of the cast would be the groove diameter of the rifle. Link to comment Share on other sites More sharing options...
Robert Prudhomme Posted February 3, 2015 Author Share Posted February 3, 2015 (edited) As Tom pointed out, a Vernier caliper (or dial caliper for those of us who have trouble reading a Vernier caliper LOL) is just as accurate as a micrometer, and can be used to make inside or outside measurements, although a 6.5mm barrel is likely about the smallest measurement one could make internally. As there are only so many calibres in the world, it is simpler to measure the outside of the cast and match that number up to known bullet diameters. For instance, if Frazier measured the outside of the cast, made from a Carcano barrel with a groove diameter of .268", and the cast shrunk by .003", he would come up with a number of .265". He would then be slightly confused, if he did not know about the shrinkage, as this would not agree with any text he was consulting. However, as most 6.5mm calibre rifles have a groove diameter of only .264", and the Western Cartridge Co. bullets he purchased also had a bullet diameter of only .264", I'm sure it did not take him long to come to the conclusion the texts were mistaken. Edited February 3, 2015 by Robert Prudhomme Link to comment Share on other sites More sharing options...
Robert Prudhomme Posted February 3, 2015 Author Share Posted February 3, 2015 Hi Chris Funny how Chuck Hawks always includes a plug for the Kennedy Carcano in his articles and tells us how it was more than capable of doing the job. Link to comment Share on other sites More sharing options...
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