Are all ~.30 caliber bullets really this interchangeable?

[Lumpy]

A post copied from Quora.com:

There is no such thing as a ".30-06 bullet". Assuming the bullet is intact enough to measure, the most you could say is it would be a .308" diameter bullet. The same bullet could be loaded in any "30 caliber" cartridge: a 30-06, 308 Winchester, 300 Win Magnum, and a dozen others.

Seriously? I thought barrel diameter required extremely specific tolerances.

[warrlac]

That's pretty much correct.

.308 diameter works in almost any 30 caliber rifle. I've loaded the same bullet in 300 AAC Blackout, .308 Winchester, 30-06, 7.62 NATO, etc. The exception would be AK47 platform. That barrel requires a .310 diameter bullet.

[870TC]

That's pretty much correct.

The exception would be AK47 platform. That barrel requires a .310 diameter bullet.

...well sorta...quite a few "30 caliber" guns use .310-.312 dia. bullets

[crbutler]

Well, the difference between the .310-.311 bullets and .308 bullets is somewhat variable.

I’ve shot a couple ak’s with .308 bullets and they shot as well as the .311’s.

Bore diameter in a .30-06 is .300, groove diameter is .308-.310 nominally. The .303 British is .303 bore diameter.

Some rifles are tolerant of the difference. The big difference would be that the bigger bullet would tend to develop higher pressure, things otherwise being the same.

[hard h2o]

I reload for the .30-30, .30-06, and .300 WSM.

One difference is tubular magazines like on many lever guns in .30-30 require a flat tip, soft point, or flex tip bullet so you do not have the tip of one bullet setting off the primer of the bullet in front of it in the magazine.

One thing to watch out for is bullet weight or length versus rifling twist weight. In loading for my various .308s I have tried something like a 125 grain on all of them. None of the ones I load for would stabilize that bullet. I have done .312 round balls in the .30-30. That was a fun little experiment. My .30-30 likes 170 grain. The .30-06 I have likes 150 to 168 grain. My savage in .300 WSM really likes 180 grain Accubonds. Bullet selection is not all about what bullet will safely run down the bore. It is also about what will be accurate, what will be stable, and what will do the intended do the job.

Cartridge nomenclature is kind of messed up in places. As was mentioned most any cartridge that takes a .308 bullet can pretty much use any .308 bullet. Some of the rounds designated 7.62 will use a .308 bullet but not all of them.

You will even see cannelures on bullets meant for crimping. That cannelure might be set up for a specific cartridge. If you load that bullet in a different cartridge the case mouth might not line up with the cannelure.

You have the usual .30 and .300 U.S. or SAAMI designation and you also have cartridges in the U.S. that are designated as 7.62 such as the 7.62x51 NATO. Then you have cartridges such as the 7.62x54R or 7.62x39 and a few other European cartridges. Normally if a cartridge is designated 7.62 in the U.S. it will use a .308 diameter bullet. In Europe and the rest of the world it could use a different diameter bullet than .308.

For the most part if you are using factory ammunition you can trust that adherence to SAAMI or CIP will take care of all of that.

[crbutler]

That’s kind of unusual.

Stabilization requires faster spin rate (shorter twist) as the bullet gets longer. If the bullet isn’t stabilizing and it’s a lighter bullet (which almost universally means it’s shorter) it should have very good stability, even if it’s not the most accurate choice in that rifle.

Of course, if the rifling is shot or if the bullet is too undersize to pick up the rifling, it will be unstable and tumble.

As to bullet choices, there may be less optimal types, but you certainly can shoot spitzers through a .30-30, it’s just not a good idea to cycle more than 1 in a magazine tube- I’ve got an encore barrel in .30-30 that loves 155 Sierra match kings. That’s one of the things about handloading is that you can make a bunch of changes.

Now, the quoted article is looking at it from a different perspective than handloaders- it looks like it’s more from a forensic point of view- and if you are dealing with a .308 bullet, you can’t tell what it was chambered in from the bullet- because of handloaders. Sure, you could pick up tooling marks to match it up with an individual barrel forensically, but if you find a .308” 147 FMJ bullet with 1-10” rifling marks engraved to a .30 level, you cannot say if it was a .308, .30-06, .30-40, .30 magnum of some stripe, or even a .30 carbine. You would need other data.

Can you load .308 diameter 147 FMJ bullets and if the particular rifle tolerates it (like mine does) you can shoot it through a 7.7 Jap Arisaka… although it doesn’t shoot to where the sights are set, it does make the same 2” grouping as the .311 bullets I’m supposed to use in it.

So the question is more what are you asking about than “you can’t tell one .30 bullet from another.”