Are .30 caliber or .308 caliber diameters different

[10mm Witness]

I am reloading for 7.62x51 for my AR 10 platform. I have been searching the local reload shops and websites for .308 projectiles. When I look up .308 projectiles for Hornady, Berger, Nosler, etc; I only see .30 caliber (.30 diameter) projectiles. I have bought .308/7.62x51 ammunition(Remington, Hornady, Fiocchi, Tulammo. They all measured .30 diameter.
What gives? Whats going on here? Do I need a true .308/7.62 diameter projectile to fit the wider lands in the barrel? (Where does one find them?) Is the .30 caliber diameter projectile still grabbing the narrower lands in the barrel?

[NSB]

The description on EVERY box of bullets spells out the exact diameter. There are several different “30” caliber bullets that aren’t exactly .308”. Example: .303 British is actually .310-.312”. You need a true .308” bullet for your gun.

[Soundguy]

If you are relaoding.. and don't know these basics.. I'm sorry.. but you need to put the gear down and pick the books back up.

Cartridge naming designations are more art than science. For instance.. 5.7 x28, .223 rem, 5.56x45 and .218 bee all use the same diameter projectiles...

[BK7saum]

Any ammunition marked .308 winchester should have a .308 bullet. Did you pull a bullet to measure or just measure the bullet sticking out of the case neck. .308 winchester or 7.62x51 is NOT loaded with 0.300" bullets.

Your 7.62x51 AR10 needs .308" bullets.

[oley55]

I wonder if the OP is misstating his confusion and is actually struggling with caliber versus bullet diameter. Not pushing midway as a source, but filtering for .308 produces many options.

https://www.midwayusa.com/bullets/br?cid=19785&Diameter=0.308+Inches

[Soundguy]

And cast bullet measurements throw in another wrench. ...

[NSB]

Every place I get bullets from (lots of places) sells .308 bullets under the heading .308 bullets, not 30 cal. I’m not sure how you’re ending up being confused about this. It sounds like you need to get a good reloading manual (I’d suggest Lyman 50th as a great place to start) and read the info in the book. It isn’t rocket science, but you DO need to have some good basic understanding before you start or you could damage your gun or yourself….maybe both. Be safe.

[1hole]

.30 caliber barrels are normally bored to .300". Normal rifling is cut .004" deep, therefore the full groove diameter of a .30 caliber barrel is .308". All ".30 caliber" bullets are made .308" so they can fill the barrel.

I know of no manufacturer who makes .300 bullets. If you're measuring .300 bullets in a box of .308/7.62 ammo (or .300 magnum) you're doing something wrong.

[Omega]

Yea, I tend to side with 1hole on this one, I have purchased many commercial 30 caliber bullets and they are all .308. When I need to reload for my 303 Brit, I have to specifically look for those instead of 30 caliber. Most places will give you the full description though, so you should be able to discern it's true measurement even if not .308.

[Baltimoreed]

No wonder my 300blackout sucks, Ive been swaging .308s down to 300. Then why isn’t it called 308blkout? Reloading is so comfusing, next thing you'll tell me that a .38 special isn’t .38. [wink wink, nod nod] More research is required.

[Finster101]

No wonder my 300blackout sucks, Ive been swaging .308s down to 300. Then why isn’t it called 308blkout? Reloading is so comfusing, next thing you'll tell me that a .38 special isn’t .38. [wink wink, nod nod] More research is required.

If you have been doing that you definately need to hit the books some more. All the reloading manuals I have show bullet diameter.

[gwpercle]

No wonder my 300blackout sucks, Ive been swaging .308s down to 300. Then why isn’t it called 308blkout? Reloading is so comfusing, next thing you'll tell me that a .38 special isn’t .38. [wink wink, nod nod] More research is required.

:lol: Please excuse me for laughing ... not at your confusion but I never thought about the name ... 300 Blackout ... and boolit diameter . Yeah you right ... and just why isn't it the 308 Blackout .

I started reloading and casting in 1967 and was just as confused about all the different names , numbers and senseless designations ... I was asking the local gun shop owner so many questions he gave me a book to read ... "Cartridges of the World " published bu Guns Digest and updated every few years . It really explained a lot ... I bought the book ... whenever a revised edition would come out I bought one ... It turns you into a Cartridge Expert , have a question ...look up everything you need to know ... how to make cases for obsolete rounds and even a little loading data in there .
If you want to become an overnight Whiz Kid on cartridges ... just pick up a copy .
Over the last 50 years I have picked up about 8 editions . The newest one The 16th Edition has info on 1500 different cartridges in it , sells for about $38.00 and if you are getting into shooting , reloading or gun history and development ... you need to have one ...worth Every penny !
Gary

[oley55]

Finster101, I fear you missed Baltimoreed's fairly obvious humor in his post, that is unless I just missed the humor in yours.

[bimus]

If I remember right Ruger mini 30 came out in 310 diameter so it could shoot 308 and 311

[Wayne Smith]

On Midway the 30 caliber boolits are .308 in diameter, simply because most 30 caliber guns are truly .308, not .300.

[gumbo333]

10MM you need to get a library of reloading manuals started. Cartridges of the World is a must. The 'caliber' stamped on the gun barrel is not always the bullet diameter, especially with all the different '300' guns.

[JohnH]

I see all kinds of goofy stuff on the 'net. The most annoying is when bullets are called "heads", as I understand it that's something you use for a hat rack or a place to relieve yourself. The other most annoying thing is "30-30" caliber. There is no 30-30 caliber. There is no 44 Magnum caliber. There is no 270 Winchester caliber. All of those are cartridges or chamberings. A cartridge is a piece of brass, with primer, powder and bullet designed to fit in a given chambering for which a firearm is chambered. Properly, caliber is a measurement of bore diameter and there can be an absolute plethora of cartridges and chamberings in that caliber. A good place to go explore this is https://saami.org/technical-information/cartridge-chamber-drawings/ SAAMI (Small Arms and Ammunition Manufacturers Institute) is to firearms and ammunition what ASME (American Society of Mechanical Engineers) is to the engineering sciences, the controlling group of standards used in manufacturing. The link is for the cartridge and chamber specifications for all the SAAMI approved cartridges. There are many wildcats which will not be found here. Enjoy learning.

[tankgunner59]

+1! If you haven't done it yet you need to, get a good reloading manual and read the instructional section in the front, then re-read it. If you have then re-read it now. I have 5 metallic cartridge loading manuals. Not only did I read each one through twice when I got them but I still read them from time to time. For two reasons, first to keep myself sharp and second for the enjoyment. Yes, I enjoy reading and especially about reloading. I too suggest Lyman's 50th, it is very basic and easy to understand.

[15meter]

Except for the boxes that say 30 Cal in big print on the box, then .308" in smaller print further down the box, for a newbie it could be confusing.

Look at the end of a Hornady box.

If he is trying to measure loaded ammo, he's probably out on the ogive, which would give someone new to rifle loading misleading measurements.

His name leads you to believe he may be more of a pistol guy than a rifle guy.

[15meter]

And keep asking the questions if you're not certain about something, better to ask the questions than hurt yourself.

With 21 posts in 8 years, looks like you are kind of a newbie here, welcome to the forum, sort of.

And I put .308 bullets in 300 H&H and 303 Savage. And .311 in .303 British. It's not confusing at all.:kidding:

Not sure there's a manual out there that has a clear explanation of the diameter conundrum except that my guess is the boys naming cartridges probably did it at the bar on a Friday afternoon.

And my personal reloading manual shelf is about 4 feet long.

And Hornady lists .303 caliber at .312, and 32 caliber at .312, and 32 caliber at .321.

https://www.vanceoutdoors.com/category.cfm/outdoors/reloading-bullets-brass/brand/hornady/CurrentPage/6

[oley55]

...The most annoying is when bullets are called "heads",...

Asleep at the wheel again I guess, but I have NEVER, EVER herd of bullets being called heads. A link or reference would be appreciated.

[Stewbaby]

I blame The US military for .30, lol (7.62 was at least used on the m14).

https://uploads.tapatalk-cdn.com/20211125/8a999e1d8a263ccb61dda33ac064b3cb.jpg

https://uploads.tapatalk-cdn.com/20211125/df9ff184c16b1616fa8bf178c57bd211.jpg

[M-Tecs]

.30 caliber barrels are normally bored to .300". Normal rifling is cut .004" deep, therefore the full groove diameter of a .30 caliber barrel is .308". All ".30 caliber" bullets are made .308" so they can fill the barrel.

I know of no manufacturer who makes .300 bullets. If you're measuring .300 bullets in a box of .308/7.62 ammo (or .300 magnum) you're doing something wrong.

Ihole is correct. There are two diameters in a barrel. The greater (major) diameter is the groove; the lesser (minor) is the bore.

The groove diameter is what you are checking bullet fit against.

Good info here https://castboolits.gunloads.com/showthread.php?323488-Redpill-me-on-bore-vs-groove-diameter-teminology

Listing the bore diameter as a Caliber is a carryover from the early days.

[15meter]

Asleep at the wheel again I guess, but I have NEVER, EVER herd of bullets being called heads. A link or reference would be appreciated.

Except for the guys around here that try to sell "stuff" on Craigslist.

"Heads" for bullets is pretty common.

[M-Tecs]

No wonder my 300blackout sucks, Ive been swaging .308s down to 300. Then why isn’t it called 308blkout? Reloading is so comfusing, next thing you'll tell me that a .38 special isn’t .38. [wink wink, nod nod] More research is required.

You set the hook well with some. You missed the purple font.

[Baltimoreed]

The manager of my local bank branch is a shooter/hunter reloader and he calls bullets ‘heads’. Only guy that I’ve ever met that does.

[Soundguy]

At our local gun store, there are usually a few reloading items..people, during the ammo shortage would try to buy the projectiles and I heard their clerk telling them they were just the heads...

[dverna]

Heads...pills...bullets...whatever

If my head hurts, sometimes I take a pill.

[1hole]

A "caliber" and correct bullet diameter is determined by the bore size.

The "caliber" of each named cartridge is wide open to the maker's desire to have a distinction for his ammo in the retail market.
Thus, off the top of my head for factory .30 caliber cartridges, we have .300 BLK.; .30 Carbine; .300 Savage; .30-30 Win; .308 Win/7.62mm; .30-06 Spring.; .300 Win Mag.; .300 Wby Mag.; .30 Rem; .300 WSM; .300 WSSM; all of them shooting .308" bullets.

It's even worse for many handgun cartridges. Like, there is nothing about a .38 Special that measures .38". And the supposed deadly 9mm is nothing more than a hot loaded .38 Special with puny, light-for-caliber .356"/.357" bullets.

All of this only means we need a loading manual for whatever cartridge and bullet weight we want to work with.

[Winger Ed.]

It's even worse for many handgun cartridges. Like, there is nothing about a .38 Special that measures .38".


I think that came from the cap & ball .36 Caliber Navy Colt days that the barrels were .357 inches in dia.

When cartridges came along, the arms makers only had to do some minimal retooling to make the new guns from the
equipment they already had for making the .36 cap & ball revolvers & little known .38 rimfire.

They called them .38s as an advertising gimmick sort of deal so you'd feel like you had more gun the the old .36 C&B was.
That held, and worked OK for .38S&W, .38 Long, and .38 Special.

Then along came the .357Mag. It sounded more cool, and would sell better than ".38 Special Extra Long" or something else
to make the average shopper feel they really had something better than just an extended .38Spec.

[bimus]

Some times after a round has been out for awhile they just change the name like the Remington 244 to the Remington 6 mm or 7 mm express to the Remington 280

[1hole]

They called them .38s as an advertising gimmick sort of deal so you'd feel like you had more gun the the old .36 C&B was.
That held, and worked OK for .38S&W, .38 Long, and .38 Special.


All the "confusing" labels for cartridges came from marketing departments, not engineering. I've read that the original ".38 Special" designation was taken from the original (specified) diameter of the loaded case at the mouth and that sounded bigger/better than ".357 Special", et al, to the marketing people. Later, the same cases were being made from harder but slightly thinner brass so ".38" no longer had any legitimate meaning at all but the label stuck. I really don't know if all of that's true but, from what I do know about deceptive advertising and successful marketing to gullible people, it sounds reasonable.

And - the .244 Rem was changed to 6mm Rem to reflect the rifling change from 1 turn in 12" to 1 in 10" to better handle 100 gr. bullets; that twist change made it a better competitor to the .243. The 6mm Rem is a slightly better "all round" varmint/medium game cartridge than the .243 Win but it came too late to save it in the market.

Oh yes, while we're on it, I sometimes read that the .243 Win is more prone to "case stretching" than other cartridges; that's nonsense.

[MUSTANG]

I must take exception with all the EXPERTS (a previous high pressure leak) on this thread. Of course there is a .30 caliber boolit that is NOT .308 caliber:

292321

or


292322


Now of course this a "Self Help" Bullet/Boolit and one must apply their own jacket (Paper).

[1hole]

I must take exception with all the EXPERTS (a previous high pressure leak) on this thread. Of course there is a .30 caliber boolit that is NOT .308 caliber:

292321

or


292322


Now of course this a "Self Help" Bullet/Boolit and one must apply their own jacket (Paper).

So, what's the end result after adding two or three of turns of paper jacket to a .300" bullet? ;)

[GregLaROCHE]

This hobby wouldn’t be as much fun, if it were too easy or logical !

[FLINTNFIRE]

Some times after a round has been out for awhile they just change the name like the Remington 244 to the Remington 6 mm or 7 mm express to the Remington 280

It started out as the 280 rem. they switched to 7mm express to try and bring new interest , they switched back because of the confusion with the 77mm rem mag , I had a older 280 rem in a 740 .

I believe the 244 rem they switched the twist in the rifles and did the switch on name to bring life into a dead one .

[gwpercle]

Asleep at the wheel again I guess, but I have NEVER, EVER herd of bullets being called heads. A link or reference would be appreciated.

I have seen it a lot ... usually not on this site and usually by newbe's ... to them a bullet is a complete loaded round . They like to call the projectile "Heads" .
That and calling Load Data ... recipes ... used to bother me ... it's data we ain't Julia Child and we ain't baking Cakes ... I try not to let either term bother me any more .
And I don't have no stinking links ... just take our word for it ... why would I lie to you .
Gary

[oley55]

I have seen it a lot ... usually not on this site and usually by newbe's ... to them a bullet is a complete loaded round . They like to call the projectile "Heads" .
That and calling Load Data ... recipes ... used to bother me ... it's data we ain't Julia Child and we ain't baking Cakes ... I try not to let either term bother me any more .
And I don't have no stinking links ... just take our word for it ... why would I lie to you .
Gary

got it, guess I'll go now and count my clips. LOL

[1hole]

Goodness. Yes, when it's easy to get terms right it's mildly irritating to read/hear the simple language of firearms and ammo get corrupted by people who should know better isn't it? Little wonder that so much gets misunderstood when people who don't know what they're talking about try to converse with people who do! Some of my verbal "favorites" include:

* Head separations that get called "incipient separations".
* Removable magazines that get called "clips."
* Cartridges that get called "bullets."
* Bullets that get called "projos" and "heads."
* Brass cases that get called "casings."
* Clumsy price snobs that call Lee reloading tools "junk."
* Saying to adjust a press to "cam over" when cam over simply means the toggle lever block can (or can't!) be rotated passed top-dead-center, so no adjustment is required.