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...r=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.

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-informat...mber-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.

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/catego.../CurrentPage/6