Carcano shooting
- Thread starter Claven2
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Like for any load development, you should start with entry level load data and work up for your rifle. Hornaday published a very specific load for these and insisted, if I recall, on Winchester magnum primers.
Hatcher ran experiments reaming 6.5 Japanese rifle to accept .30-06 rounds. Upon firing, there were major over pressure signs, but the bullets squeezed down and exited as 6.5mm projectiles.
These would have been lead core, but not clear if they were fmj, soft points, etc. Need to go find my copy.
According to the Textbook of Small Arms 1909; Greece, Italy, Holland and Romainia all used the large 268-269 groove diameter but only the Italians used a bullet larger than 264 and Japan used a 260 bullet. I have no idea if this is all true. On p219 of "Crown Jewels" it says the groove diameter of the 6.5x55 was to pass a gauge of 6.75mm (this is .266) and a bullet of .263" with a max of .264".
The open base bullet is likely for manufacturing reasons.
My guess is that some of the accuracy woes of Carcanos is caused by the short sight radius of the Carbines. The Swedes are known for accuracy and the spec is for .266" with a 263" bullet, but the the long 96 is the most common.
The open base bullet is likely for manufacturing reasons.
My guess is that some of the accuracy woes of Carcanos is caused by the short sight radius of the Carbines. The Swedes are known for accuracy and the spec is for .266" with a 263" bullet, but the the long 96 is the most common.
Case in point - if true, original sources would confirm that. That is not to say that it doesn't cause some obturation - it is said that: non-gas-checked cast lead bullets obturate a lot (the softer the lead the more); followed by gas-checked lead; then open base jacketed; then closed base jacketed with thin jackets; etc. However, I have shot many 218 gr jacketed Open Base Boat Tail 8X63 Swedish bullets and recovered them and their bases remained the same Boat Tail they began with, so I am skeptical....
The problem is that the reason for the open base has grown from expediency in manufacturing, to the need for the bullet to obturate.
We all know the old "Pot Roast Story":
A newly-wed man would watch his wife would cut an inch off from both ends of meat for pot roast before putting it into the oven. When he asked why, she answered, “That’s how you are supposed to cook it.” Not satisfied with this answer he pressed further until she said she learned to do it this way from her mother.
The husband calls up his mother-in-law and asks her why she cuts off an inch from each end of the pot roast. She answers, “That’s how you cook pot roast.” He presses further until his mother-in-law says she learned to do it that way from her mother.
So the man calls up his wife’s grandmother and asks her the same question about why you cut an inch off each end of the pot roast before putting it into the oven. He still can’t figure out why cutting off good meat is a requirement for cooking a pot roast. She says, “My mother did it this way. Let me call her.”
She calls her elderly mother and asks her why she used to cut the ends off the pot roast before cooking it. The great-grandmother laughs and says, “We used to be very poor and didn’t own a lot of cookware. I cut the ends off so the meat would fit into my only pan!”
The husband calls up his mother-in-law and asks her why she cuts off an inch from each end of the pot roast. She answers, “That’s how you cook pot roast.” He presses further until his mother-in-law says she learned to do it that way from her mother.
So the man calls up his wife’s grandmother and asks her the same question about why you cut an inch off each end of the pot roast before putting it into the oven. He still can’t figure out why cutting off good meat is a requirement for cooking a pot roast. She says, “My mother did it this way. Let me call her.”
She calls her elderly mother and asks her why she used to cut the ends off the pot roast before cooking it. The great-grandmother laughs and says, “We used to be very poor and didn’t own a lot of cookware. I cut the ends off so the meat would fit into my only pan!”
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I have Hatcher's Notebook (it's also available free in PDF format and is searchable https://ia601307.us.archive.org/1/items/Hatchers_Notebook/Hatchers_Notebook_text.pdf) and all I could find that was similar to that was 7.7 Jap rechambered to 30-06 and having the unsupported base splitting, and the widely-known story of boys shooting 35 Rem in a 7.7 Jap barrel. Here it is:
The apparent "knowledge" gleaned from this is that Hatcher proved that Arisaka actions are very strong AND that pressure skyrockets when larger projectiles are fired in a gun due to the resistance of the bullet being squeezed down so much. Going back to the original printed source, however, he said only the former. The actual original source (the events as told by the boys) is not quoted, so we don't know if it even happened, and if it did was was there some kind of bore obstruction, i.e. a squeezed down bullet lodged in the barrel and a second fired bullet that followed it?
We just don't know and I pointed this out years ago on another forum, and suggested that if it happened, the bullet would have greatly compressed the powder, and the neck would have been severely pinched, so it might have been that, not the bullet being sized down, and I was savaged as having called out Hatcher - and that's not even what I did, all I did was restate what he did say.
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I've used the 264 (factory) and 268 PPU (reload) in full length carcanos with success, but I've had no luck with either with cavalry carbine. I also got a batch of cast bullets from Jet bullets before he retired but it still keyholed in the carbine. The bore is decent, so I'm trying to figure out what to do next
Which model of Carbine specifically? Some of the earlier ones are made with cut back full size rifle barrels, and due to the gain twist that reduces your effective twist rate at the muzzle. I can't recall exactly which guns suffer from this issue though.
Maybe it is - maybe. That story has many versions, and even includes various people who say they knew the guy, and the story that it's now in the NRA Museum to..................... Not a wild goose chase I'll go on.
IMO that tale is probably a conflation of what Hatcher wrote (already shared) and this piece from P.O. Ackley. The interesting part of this is that Ackley did not believe that even larger reductions in bullet diameter upon firing had much effect on pressure. I've seen recent tests where a bullet about 10 thou oversize actually saw a reduction in pressure. Counter-intuitive, but physics doesn't care about our intuition.
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Andy, the exposed lead base on 8x63 is .145", while the bullet diameter is .323. This is the average of 5 projectiles I just measured. The diameter of the jacketed portion is more than double the exposed lead, and the jacket is shaped inward sharply. A sudden jet of pressure to the base of such a bullet has many times the area of jacket to push on than the exposed lead. If anything, with this bullet design, I'd expect a small reduction in the diameter of the exposed base upon firing.
Some PPU loaded ammo has .264 bullets, some .268 bullets.
Page 7 of this product lineup has their carcano stuff, the * shows which have .268 projectiles as per the foot note on the page.
https://www.prvipartizan.com/download/PPU_2018.pdf
Also, Hornady and their thicker jacket isn’t due to the gain twist rifling, it’s due to the extra deep cut of the rifling. The first Italian smokeless powder was stupid hot burning and was ruining barrel life, so they kept the same land diameter, cut deeper grooves and used the previously mentioned bullet with a ‘driving band’ section to reduce the bearing surface between the bullet and barrel. Bore was .257, .268 grooves according to Hornady manual. They also used grain twist rifling for longer barrel life as well. C&Rsenal on YouTube explains this well in their Carcano video.
Italy eventually switched powders and dropped the gain twist rifling (didn’t actually do much), but didn’t change the bullet design or the deeper cut rifling, as that would be a logistical nightmare.
Page 7 of this product lineup has their carcano stuff, the * shows which have .268 projectiles as per the foot note on the page.
https://www.prvipartizan.com/download/PPU_2018.pdf
Also, Hornady and their thicker jacket isn’t due to the gain twist rifling, it’s due to the extra deep cut of the rifling. The first Italian smokeless powder was stupid hot burning and was ruining barrel life, so they kept the same land diameter, cut deeper grooves and used the previously mentioned bullet with a ‘driving band’ section to reduce the bearing surface between the bullet and barrel. Bore was .257, .268 grooves according to Hornady manual. They also used grain twist rifling for longer barrel life as well. C&Rsenal on YouTube explains this well in their Carcano video.
Italy eventually switched powders and dropped the gain twist rifling (didn’t actually do much), but didn’t change the bullet design or the deeper cut rifling, as that would be a logistical nightmare.
A bullet is made with a piece of jacket material, punched into a test-tube shape, a lead slug then gets inserted into the tube and the combination is hit with a forming die. The open end of the test tube can be formed as the nose or the base, depending on the needs of the bullet.
Military bullets must be solid nose, so the open end of the tube becomes the base.
Obduration does not require an open base. The yield limit of the bullet is around 10 to 20,000 psi. When you hit it with 50,000 psi, it compresses and forms the shape of the barrel.
An undersized bullet can allow gas cutting, which will blow the accuracy.
The final determinant of accuracy is the barrel crown and the bullet base shape. A perfect crown and good barrel can shoot a boattail bullet well. Anything less than perfect (most military rifles) will do best with a flat base bullet (i.e. a soft point or hollow point). The muzzle gasses will not upset the bullet because of irregularities of the bullet base. The least accurate is the open base, because the base is irregular and the muzzle gases upset the bullet.
If you want cheap but accurate bullets for your 30 cal or 303, buy the flat base soft point bullets - not the FMJ.
This last recommendation and explanation came to me from Joyce Hornady. He talked me out of buying his 308 FMJs. He was right. I got almost match bullet performance form his 165 and 150 308 soft point bullets.
Military bullets must be solid nose, so the open end of the tube becomes the base.
Obduration does not require an open base. The yield limit of the bullet is around 10 to 20,000 psi. When you hit it with 50,000 psi, it compresses and forms the shape of the barrel.
An undersized bullet can allow gas cutting, which will blow the accuracy.
The final determinant of accuracy is the barrel crown and the bullet base shape. A perfect crown and good barrel can shoot a boattail bullet well. Anything less than perfect (most military rifles) will do best with a flat base bullet (i.e. a soft point or hollow point). The muzzle gasses will not upset the bullet because of irregularities of the bullet base. The least accurate is the open base, because the base is irregular and the muzzle gases upset the bullet.
If you want cheap but accurate bullets for your 30 cal or 303, buy the flat base soft point bullets - not the FMJ.
This last recommendation and explanation came to me from Joyce Hornady. He talked me out of buying his 308 FMJs. He was right. I got almost match bullet performance form his 165 and 150 308 soft point bullets.
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FWIW, it was American Rifleman, May, 1959, page 52. I haven't found a scan yet, but found the issue info in some of my old notes.
Here's the original text:
One of the things about these rifles is that their bores can be anywhere from .265-.270 diameter.
If you can find exposed lead base bullets, they will usually obturate well enough for 4 inch or less groups at 100yds.
Our present bullet makers now only seem to want to produce bullets for tight tolerance, high precision, modern rifle bores.
I'm quite disappointed that "Berry's Bullets" hasn't come out with several lines of their bullets with exposed lead bases. IMHO there would be a large market for such bullets, once hand loaders realized how well such bullets take up the discrepencies between bores.
If you can find exposed lead base bullets, they will usually obturate well enough for 4 inch or less groups at 100yds.
Our present bullet makers now only seem to want to produce bullets for tight tolerance, high precision, modern rifle bores.
I'm quite disappointed that "Berry's Bullets" hasn't come out with several lines of their bullets with exposed lead bases. IMHO there would be a large market for such bullets, once hand loaders realized how well such bullets take up the discrepencies between bores.
