Question for you reloaders

Why is it that the U.S. 30 cal. guns like the 30-06, 308nato and the 30-30 all of which are called 7.62s use a .308 bullet and the Russian guns like the 7.62X39 and 7.62X54 use a .310 bullet but all of them are called 7.62?? I was told why years ago and want to see if any of you have been told the same thing..

Could be to compensate for bore erosion due to corrosive primers in old Russian ammo, just a guess.

Seems to me that it has been standard practice for our adversaries to use ammunition that we cannot chamber, but that can chamber our ammunition if need be...

Ron..

I think the bullets for the AK-47 are actually .311 (7.90), but hey, whats a few ten thousandths among friends!


.308 is 7.82

I just went out to the truck to grab the .45 Colt dies that I bought this afternoon. $45.00 for a danged set of dies!!!!

Used to get them for $15-20!

Gene

And PS. I dont know the answer to your question.

Why is a .270 called that when it is a necked down .30-06 case, but a .25 caliber version is a .25-06. ?

I have a 4 page paper I picked up at a rifle marksmanship class in college. It is all about cartridge nomenclature. It basically has no rhyme or reason. Drive a guy nuts!!

7.62mm is equal to 30 one hundreths of an inch or .30 caliber. When a .30 cal barrel is made, first a .30 inch hole is drilled through the center, this is where the .30 cal. designation comes from. Then the spiral grooves are cut in the barrel, so naturally the bullet diameter must be equal to the barrel's groove diameter. I would say the Russians made their rifleing slightly deeper than did the US, thus the need for slightly larger bullets.

Gene you need to put your glasses on as per the re-loaders manual the 308 like I said is 7.62 not 7.82 like you said. LOL Yep I have the dies for the 30-06 and 308 an have used the same bullet in each so it has to be 7.62

.30 caliber rifles have a .300 inch bore and the rifling diameter is .308, or 7.62 mm. The bullet size is the same size as the rifling, or.308 inches/7.62 mm.

For the Russian cartridges, 7.62 mm denotes the bore diameter, not the diameter of the bullet or rifling, which are obviously larger than the bore.

Old: actually, Gene's right on the money--the conversion factor from metric to inch is 0.03937. Divide .308 by 0.03937 and it is 7.82, regardless of what the round is actually officially named, which proves his other point--there is no "one" reason why bullet size and caliber don't match up. Yes, there are several common ones, such as measuring land size versus bullet size, but there are plenty of exceptions to any rule you want. A .38 Special and a .357 magnum use the same bullet size, and a .44 magnum's bullet is actually 0.429"! It usually boils down to what they folks in the marketing department figure will sell, rather than being mathematically correct.

I have the same question about .357 and .38 special. What is the bore size on a .357 that it canshoot .38 caliber bullets.

This has nothing to do with your question or reloading,just thought my latest creation from track of the wolf would be interesting to any black powder shooter on here. Took me about 2 weeks of spare time to build it..50 Cal. Percussion in the Hawken style.Brass wing front sight,black v slot for the rear sight,at 50 yards aim high,it will be right on.

if you actually convert those numbers, your reloading manual is wrong. looking at the starrett metric/inch chart right now..

0.300" = 7.62mm

from all I know your 30 cal bullet is actually going to measure .308" as the 30-06 is also specified for a .308" bullet as well as the 30-30.

7.62-39 has the .312" bullet diameter even though we know 7.62 does not equal .312"

basically I think the answer to your question is rifling depth.

I either typed it wrong, or read it wrong, but the 7.82 is a mistake on my part.

Gene

Don't forget 7.5 french MAS it is called 30 caliber 308 etc it is neither and a disaster to reload for.

A 38 has a bore of 357 and is loaded about half as much powder as the 357 and the 357 has a bore of 356.
Now just as a reference using Bullseye powder the 38 you load with 3.4 grain with a 110 grain bullet but in the 357 you use 7 grain with the same size bullet. The 357 is pretty much a heavier 38 and that is why it is called a mag.

Also dont confuse with a 38 S&W (late 1800s to early 1900s)

They were .360 if I remember. You can shoot a 38 spl in a 38 S&W but not the other way around. But the 38 spl is a little more powerful so you want to be careful.

Not to add any confusion, some other things kind of related about .308's, there seems to be 2 specifications for .308's military with thicker brass and civilian/hunting brass are slightly different. I don't know a heck of a lot about the details but have read a little on it, off the internet, at some point in the past, one would have to really look at the information. I recall that each type of brass was specified by different reference standards, like SAAMI or similar to a ASME, for example. I know that military brass being Berdan primed, is not desirable for reloading and I assume that has not changed. I bought some 1x fired brass from a shop one time that I thought was non military but recall that some of the casings that I filled with powder were almost full, with standard loads for a 130grain hollow point,was using an IMR powder maybe a 3031, I would have to look at the can to see. I was reloading for my springfield m1a, which the mfr does not recommend due to headspace issues, I used the correct die, a special RCBS semi auto die, and form fitted my case to my chamber and had no issues at all. Those rounds grouped quite well and were very effective on whitetail deer, from a rifle really designed for other purposes. Kind off the topic here, but it sure was an interesting one to re-load. I think the seemingly thicker wall brass, I was able to load and use, something was a but odd there. I also recall trying to chamber some factory hunting rounds for this rifle and there was a headspace or similar issue, they would not chamber correctly, of course I realized that there was the potential for this due to the type of rifle it is. One last thing I recall was that the old timer who runs the gun shop, a Korean War veteran and someone who helped close our famous Springfield Armory in '68, told me to avoid certain year military ammo, because it could be M60 machine gun ammo, with higher chamber pressures, I thought all that military ammo was the same, 'cept the M60 which I have fired, contains tracer rounds, same of which I have fired out of this rifle, no idea if they came off a M60 ammo belt or not. I don't really know all the facts on any of this, be it true or not, but there seems to be an awful lot to know or learn, it reminds me of welding, so many different things and variables to consider.

It was done entirely by intent of the Soviets, they could fire our 7.62 (.308) with thier weapons whereas we could not use there ammo, the same with the 5.56 (.223).
Lou

Lou, that's an interesting theory, except that the 7.62x54 Russian rimmed cartridge predates not only the 7.62 NATO, but also the venerable .30-06 and even the elderly .30-40 Krag. In 1891, when the 7.62x54 came out, the standard US military cartridge was the blackpowder .45-70!

I have to retract what I said. If I'd bothered to do the math, I would have realized that 7.62 mm equals .300, not .308.

I will say that the 7.62x39 uses the same bullet and bore diameter as the much older 7.62x54R. And the 7.62x54 dates back to a time before there was consensus on what calibers would become more or less standard. By the way, the bullet diameter of the Russian "7.62" cartridges is very close to that of the almost equally old .303 British: .313 for the Russian cartridges, .311 for the British.

Nice work, John.

The .38 Special actually uses a .35 caliber bullet. The cases of the .38 and .357 cartridges are .38 inches in diameter. I believe the designation "38" comes from an older cartridge whose bullet diameter was the same as its cartridge case diameter.

The main dimensional difference between the .38 Special and .357 Magnum cartridges is that the .357 is about an eighth of an inch longer. That is to prevent the use of .357 cartridges in .38 Special revolvers. .357 cases are also a bit thicker. But the REAL difference between the two is that the .357 is loaded to much higher pressures than the .38. The .38 Special was originally a black powder round, and its case capacity is underutilized with modern propellants. The .357 just uses up that extra case capacity.