bullet size conversion question

[bean]

just so everyone understands, im not looking to try to "build" my own bullets or anything like that, i am just asking because its just something i could never get a straight answer on.

what im wanting to know is, obviously my m44 shoots 7.62x54r, which is a metric size. just to see how this bullet stacks up to standard size bullets (such as a .308) how do you convert that over? i am just a little confused on these things, just like a .30-06, what does that even mean?

i am new to guns and i just wanted a better understanding of what different bullet sizes ment and what they actually are. i hope its not a dumb question, i have just been wondering about this.

hopefully you can understand what im saying.

[FINNADDICT]

7.62x54r is typically .310 in size. 30-06 means .30 caliber of the year 1906.

[bcposton]

Wow Finn I just learned something new about the .30-06!

To the OP - If I remember right most of your standard .30 caliber bullets will measure at .308 - this would include .308, .30-06, .30 Carbine etc. The 7.62 is a little more variable depending on when and who made it.

[millman]

7.62 x .03937 = .300
.30 is the bore diameter. The groove diameter is about .312. Hence you use .311 bullets.
.308 and 30/06 also have a .30 bore diameter, but the have a a groove diameter of .308. Hence you use .308 bullets in them.

[Greasemonkey]

All most any round can and generally will have a metric equivalent size, 7.62x63mm =.30-06, 7.62x33mm = .30 Carbine.

The one kink in the European military cartridges, are these off the top of my head that can use a standard .308 bullet is the 7.5 Swiss and 7.5 French.

My understanding is the standard the U.S uses is the bullet groove diameter which uses the inch convention. The European standard uses the bullet land diameter and uses the metric convention.

[FINNADDICT]

All most any round can and generally will have a metric equivalent size, 7.62x63mm =.30-06, 7.62x33mm = .30 Carbine.

The one kink in the European military cartridges, are these off the top of my head that can use a standard .308 bullet is the 7.5 Swiss and 7.5 French.

My understanding is the standard the U.S uses is the bullet groove diameter which uses the inch convention. The European standard uses the bullet land diameter and uses the metric convention.

Don't forget the M/28-30 which has a 0.3082 bore at the least when they were new.

[desdem12]

7.7 Jap is also 310 or so and 7.65 argentine is .312

[Siam]

7.62 x .03937 = .300
.30 is the bore diameter. The groove diameter is about .312. Hence you use .311 bullets.
.308 and 30/06 also have a .30 bore diameter, but the have a a groove diameter of .308. Hence you use .308 bullets in them.

My math seems to be a little different. 7.62 mm divided by 25.4 mm =.30 cal. 2.54 cm = 1". Where does .03937 come from? Probably real simple but it beats me.

[Junk Yard Dog]

If the fate of the world hangs on my ability to solve math problems at this hour ( or any hour ) then we are all gonna die.

[Themosinkid95]

.30-91 I think I just resolved this

[Longcolt44]

This is why I'm friends with Millman. I just call him.

[Flyin Brian]

Definitely not a dumb question, Bean. You've got some good answers above, especially what Millman wrote, although he didn't go into much detail ;)

I always find it helps to think of a barrel as a piece of tubing. Prior to having the rifling cut in the barrel, it really is just a tube. When the rifling is cut, they cut a pattern of grooves... 2, 4, 5, 6 grooves, etc, depending on what kind of rifle and who is making it. The area where the grooves are cut are called... wait for it... grooves!! The area where they did not cut and the original inside diameter of the tubing remains, are called lands. One of the confusing things is some cartridges are designated by the measurement of the lands and some are designated by the measurement of the grooves... and some are just brand names to REALLY confuse things, or they came about because of a very old designation (38 special is a good example, it shoots .358 bullets now, but originally it used heeled bullets that look like a mushroom head and were the same size as the case, which was .38", hence the name original name 38 short).

A 30-06 uses .308 bullets because the grooves measure .308, but the cartridge is designated as a .30 caliber which is the measurement of the bore at the lands - .3 inches (aka 7.62mm). A Mosin shoots a 7.62X54r which is also a .30 caliber (the lands are usually .300 to .303) but the rifling has been cut a little deeper so the grooves measure .310" or .311 or even .314".

The 308 Winchester cartridge is a .30 caliber... but the cartridge designation is the bullet size or the measurement of the grooves... .308"

303 British is a .303 bore (the tube before the rifling was cut) but the grooves measure .311, so you would use .311 bullets.

7.62 mm is .3 inches, period. 7.82mm is .308" and 7.9 is 3.12"

BTW, many times you will hear people talk about bore size when they really mean "groove size", but since I do it all the time myself I don't trip on it too hard ;)

[Junk Yard Dog]

[FINNADDICT]

Excellent early morning lesson.

Very well said Flyin Brian.