Someone please school me up. You buy .30 cal bullets to load all .30 cal variations. You buy the same bullet for .308, so what's up with the .008?
Sendit
any .308" bullet is .30 caliber.
any .277" bullet is .270 caliber
any 7mm bullet is .284 caliber
any .429 or .430" bullet is a 44 caliber
any 6.5mm is .264 caliber
any 6mm bullet is .243 caliber
its not hard until you get into cast boolits, but thats another discussion.
any .277" bullet is .270 caliber
any 7mm bullet is .284 caliber
any .429 or .430" bullet is a 44 caliber
any 6.5mm is .264 caliber
any 6mm bullet is .243 caliber
its not hard until you get into cast boolits, but thats another discussion.
.30 caliber is the diameter of the gun/barrel _bore_. Not the groove diameter, the bore (the hole bored prior to any rifling being made) diameter. Same with 6.5 mm, which is 0.256"; that's the bore diameter.
Bullets must be sized to fill the grooves, and .30-cal grooves were standardized a century-ish ago at 0.004", so bullets for a .30 cal (bore diameter of 0.300") measure 0.308" in diameter (there are grooves on each side of the bore, so 0.004" x 2 = 0.008" additional diameter beyond bore diameter).
.303 caliber bores take .311" bullets because their grooves are also 4 thou deep.
Smaller caliber guns tend to use smaller groove depth.
Bullets must be sized to fill the grooves, and .30-cal grooves were standardized a century-ish ago at 0.004", so bullets for a .30 cal (bore diameter of 0.300") measure 0.308" in diameter (there are grooves on each side of the bore, so 0.004" x 2 = 0.008" additional diameter beyond bore diameter).
.303 caliber bores take .311" bullets because their grooves are also 4 thou deep.
Smaller caliber guns tend to use smaller groove depth.
I never got into wondering the "WHY?" Of all this, but it's a good question. I've just always excepted the fact that .30 cal rifles for the most part are .308 diameter bullets. 9mm is .355-.356, .38 and .357 are of course .357, etc... it's all a big mess. You just gotta pay attention.
7.62 mm for Russian cartridges is .311 in most cases while for NATO standards it is just .308 cal such as .308 win or .30-06. 9mm Russian cartridges are also bigger, around .365 I believe and ours are .355-.356. Big big mess but not too hard if you have a good reloading manual. Mine lists actual bullet diameter for each cartridge.
7.62 mm for Russian cartridges is .311 in most cases while for NATO standards it is just .308 cal such as .308 win or .30-06. 9mm Russian cartridges are also bigger, around .365 I believe and ours are .355-.356. Big big mess but not too hard if you have a good reloading manual. Mine lists actual bullet diameter for each cartridge.
Simple, British and Soviet Block/ChiCom and Finish have 30 cal bores that go from .308 to .309 to .311. If you're not sure, ask about the rifle you're dealing with. I do load for some of the odd ball ".30" cal rifles. Lapua and Sierra makes the .30 cal bullets in the non-standard bore sizes.
True, but that's groove diameter, not bore diameter. The variation is from lack of agreement & standardization.
SAAMI in North America, or the CIP in Europe are the keepers of the standards. I don't know what China or Russia or anyone else use at this point.
SAAMI | Sporting Arms and Ammunition Manufacturers' Institute
http://www.cip-bobp.org/
SAAMI in North America, or the CIP in Europe are the keepers of the standards. I don't know what China or Russia or anyone else use at this point.
SAAMI | Sporting Arms and Ammunition Manufacturers' Institute
http://www.cip-bobp.org/
Even with standardization, if you compare CIP and SAAMI drawings, it's not uncommon to find millimeters and inches that don't always match as exactly as the number of decimal places given would allow them to with a precise conversion. Probably historical conversion errors or some such thing. Certainly some bullet diameters are historical artifacts, as well, coming from before standardization when a lot of bullet molds were made to suit a particular gun. This is why there is more than one lead ball diameter that is called ".44" or is called "36".
Speaking of the .36, the reason that same bullet diameter is called .38 is the chamber diameter is about .380". The naming, then, appears to be a holdover from when early rimfire 38's used bullets with rebated bearing surfaces that were the full width of the case, like a .22 Rimfire still is today. Rimfire brass dimensions may have been a starting point for later centerfire designs. The 44 Special case is .456" close to the old .45 bullets (.454") so it was probably taken from something that was once a .45" with a rebated bullet bearing surface and then reduced it to .429" for the non-rebated design, which happened to come out that size. But why then name it a "44" instead of a "43"? Maybe it's just a half-way-inbetween number, or maybe it's pre-standardization marketing based on the bigger-is-better principle. I don't know.
Speaking of the .36, the reason that same bullet diameter is called .38 is the chamber diameter is about .380". The naming, then, appears to be a holdover from when early rimfire 38's used bullets with rebated bearing surfaces that were the full width of the case, like a .22 Rimfire still is today. Rimfire brass dimensions may have been a starting point for later centerfire designs. The 44 Special case is .456" close to the old .45 bullets (.454") so it was probably taken from something that was once a .45" with a rebated bullet bearing surface and then reduced it to .429" for the non-rebated design, which happened to come out that size. But why then name it a "44" instead of a "43"? Maybe it's just a half-way-inbetween number, or maybe it's pre-standardization marketing based on the bigger-is-better principle. I don't know.
Trivia:
the .25 Caliber is either .250" Bore/.257" Groove diameters OR .243" bore/.250" Groove diameters depending on whether you are Talking about Rifle or Handgun.
the .32 Caliber also has Different CASE dimensions (.318" or .337" Diameters) for similar cartridges. and bullets of about .312" diameter.
Best Regards,
Chev. William
the .25 Caliber is either .250" Bore/.257" Groove diameters OR .243" bore/.250" Groove diameters depending on whether you are Talking about Rifle or Handgun.
the .32 Caliber also has Different CASE dimensions (.318" or .337" Diameters) for similar cartridges. and bullets of about .312" diameter.
Best Regards,
Chev. William
Bullets are easy: you look in one of your many manuals or check Google.
caliber designation could be the groove diameter, the bore diameter, or the cartridge case outside diameter. Then there is changing it to sound better to consumers (i.e., why do most .223 Rem rifles use 0.224" bullets? How many even bother to slug their barrel to match a jacketed bullet to actual groove diameter and how many just assume that the normal bullet size is correct?).
If we go by SAAMI specification for industry (which only apples to ammunition makers who have to produce safe ammo for ALL firearms so chambered, the .223 Rem takes bullets from 0.2215-0.2245", while groove diameter can range from 0.224-0.226". So based on a SAAMI chamber, 0.224" bullets would be the minimum most should be using for their own custom ammo.
Then there is cartridge nomenclature that varies from country to country.
Just something to accept and not dwell on.
Don't worry, Big Brother will take over one day and standardize it all. Of course, you won't be shooting ANYTHING when that happens.
caliber designation could be the groove diameter, the bore diameter, or the cartridge case outside diameter. Then there is changing it to sound better to consumers (i.e., why do most .223 Rem rifles use 0.224" bullets? How many even bother to slug their barrel to match a jacketed bullet to actual groove diameter and how many just assume that the normal bullet size is correct?).
If we go by SAAMI specification for industry (which only apples to ammunition makers who have to produce safe ammo for ALL firearms so chambered, the .223 Rem takes bullets from 0.2215-0.2245", while groove diameter can range from 0.224-0.226". So based on a SAAMI chamber, 0.224" bullets would be the minimum most should be using for their own custom ammo.
Then there is cartridge nomenclature that varies from country to country.
Just something to accept and not dwell on.
Don't worry, Big Brother will take over one day and standardize it all. Of course, you won't be shooting ANYTHING when that happens.
There is no consistent naming convention for cartridges and, where rifles are concerned, no hard and fast rules for what "bore" means. Even with shotguns, 2, 4, 8, 10, 12, 16, 20 and 28 bore offerings are so-named because it takes that many lead balls to equal a pound, but the .410 shotgun is a diameter measurement.
Part of the challenge (and the fun?) of becoming a gun nut is learning all these little nuances. It can be intimidating at first, but the acquisition of knowledge usually is.
Part of the challenge (and the fun?) of becoming a gun nut is learning all these little nuances. It can be intimidating at first, but the acquisition of knowledge usually is.
Yeah,not much standardization.Other that Nato designations,it is driven by marketing people. Groove or land measurements,or rounder up to a spiffy name. It does make it less clinical sounding though.
The military specs on 30 cal bores have a 0.003" diameter span, from .2985-.3015", and the groove diameters are .3065-.3095". You could say it is nominal diameter ±0.0015". The SAAMI standard is .300-.302 bore, and .308-.310" groove. Custom barrels are very precise, so you can order anything their tooling can do.
.308 Palma match barrels are made with .3065" grooves. The thinking is that staying supersonic all the way to the target matters, so they want maximum pressure for velocity, but don't want too fast a spin for the short 155 grain bullets, so they go to a slower twist than standard (13-14 turns per inch are common) but a narrower bore and groove diameter.
BigBear,
I hear what you are saying, but the dimensions don't add up very well. The .44 Special is a .44 Russian with lengthened case. The .44 Russian started out as a special order for the Russian army. At the time, S&W produced revolvers in .44 S&W American, which used a heeled bullet, and the Russian general interested in procuring revolvers for that army apparently liked the S&W product, but objected to the heeled bullet as a dirt and debris collector (anyone who's dropped a .22 rimfire round in the dirt knows exactly what he was talking about). So S&W came up with the 44 Russian cartridge to eliminate the heeled bullet for him. The .44 S&W American had a case diameter just ahead of the rim of .440" and it reduced slightly to .438" over the heel of the bullet. The bullet bearing surface was 0.436" diameter. But if you started with the .44 S&W American case and fit it to the common .430" lead bullet, you would have a neck wall only 0.004" thick, which is awfully thin and is less than the minus 0.006" thickness tolerance usually allow for a cartridge diameter. So that number assumes a maximum diameter case. I don't know the diameter of the heel on the .44 S&W American's bullet, but it would likely have been narrow enough that the brass would be thicker than 0.004". If the brass were 0.012", for example, as is common in revolver brass today, the heel would be 0.412" and a bullet that merely reduced to the diameter of the heel would have to be that small, and not .429-430".
The current SAAMI standard for the .44 Special calls for the case of the loaded cartridge to be 0.4505"-0.4565" diameter at the mouth, which is what suggested to me adaptation of a .45. But that's in modern terms. The second half of the 19th century saw some cartridge caliber designations move from bore diameter to groove diameter, probably for marketing reasons, and the old .44's were often .45's in current terminology. They also often cut rifling deeper in those days for the pure lead bullets they often used. IIRC, the Colt Walker .44 had a .440 land diameter (bore diameter) and a .456" groove diameter, and wanted a .457" ball for a snug fit. I may be off a couple thousandths here and there, but the point is that it was a .45 in modern terminology.
Anyway, the .44 Russian, whose brass was later lengthened to create the .44 S&W Special, seems to me to have started with a case diameter that was suited to a heeled bullet of what we would today call a .45 caliber. Possibly drills and chamber reamers for the .46 Rimfire were adapted by narrowing the throat. The .46 Rimfire was a cartridge designed for Remington 1858 revolver cartridge conversions. It had a 0.456" heeled bullet and a case maximum dimension of 0.458", so it comes close to the .44 Russian case.
But I don't actually know what the S&W engineers were thinking at the time. I don't know if a record of their reasoning even exists. It would be interesting to know, though.
.308 Palma match barrels are made with .3065" grooves. The thinking is that staying supersonic all the way to the target matters, so they want maximum pressure for velocity, but don't want too fast a spin for the short 155 grain bullets, so they go to a slower twist than standard (13-14 turns per inch are common) but a narrower bore and groove diameter.
BigBear,
I hear what you are saying, but the dimensions don't add up very well. The .44 Special is a .44 Russian with lengthened case. The .44 Russian started out as a special order for the Russian army. At the time, S&W produced revolvers in .44 S&W American, which used a heeled bullet, and the Russian general interested in procuring revolvers for that army apparently liked the S&W product, but objected to the heeled bullet as a dirt and debris collector (anyone who's dropped a .22 rimfire round in the dirt knows exactly what he was talking about). So S&W came up with the 44 Russian cartridge to eliminate the heeled bullet for him. The .44 S&W American had a case diameter just ahead of the rim of .440" and it reduced slightly to .438" over the heel of the bullet. The bullet bearing surface was 0.436" diameter. But if you started with the .44 S&W American case and fit it to the common .430" lead bullet, you would have a neck wall only 0.004" thick, which is awfully thin and is less than the minus 0.006" thickness tolerance usually allow for a cartridge diameter. So that number assumes a maximum diameter case. I don't know the diameter of the heel on the .44 S&W American's bullet, but it would likely have been narrow enough that the brass would be thicker than 0.004". If the brass were 0.012", for example, as is common in revolver brass today, the heel would be 0.412" and a bullet that merely reduced to the diameter of the heel would have to be that small, and not .429-430".
The current SAAMI standard for the .44 Special calls for the case of the loaded cartridge to be 0.4505"-0.4565" diameter at the mouth, which is what suggested to me adaptation of a .45. But that's in modern terms. The second half of the 19th century saw some cartridge caliber designations move from bore diameter to groove diameter, probably for marketing reasons, and the old .44's were often .45's in current terminology. They also often cut rifling deeper in those days for the pure lead bullets they often used. IIRC, the Colt Walker .44 had a .440 land diameter (bore diameter) and a .456" groove diameter, and wanted a .457" ball for a snug fit. I may be off a couple thousandths here and there, but the point is that it was a .45 in modern terminology.
Anyway, the .44 Russian, whose brass was later lengthened to create the .44 S&W Special, seems to me to have started with a case diameter that was suited to a heeled bullet of what we would today call a .45 caliber. Possibly drills and chamber reamers for the .46 Rimfire were adapted by narrowing the throat. The .46 Rimfire was a cartridge designed for Remington 1858 revolver cartridge conversions. It had a 0.456" heeled bullet and a case maximum dimension of 0.458", so it comes close to the .44 Russian case.
But I don't actually know what the S&W engineers were thinking at the time. I don't know if a record of their reasoning even exists. It would be interesting to know, though.
If the OP isn't confused after 19 "answers" then he's a better man than I. But to add a bit more "mud", much of cartridge/bullet/barrel designations are "historical lore" and not real measurements, hence the 36 cal. black powder revolver used .357" bullets...
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