.30 cal FMJ rounds, what makes them better then 5.56 FMJ?

[Jenrick]

As I am currently pondering purchasing a M1A, my thoughts naturally turned to the ammunition it was designed to shoot. Most people will tell you that an FMJ round in the .30 range is more effective than an FMJ round in the .20's and provide a variety of tables and data to support that (along with a lot of anecdotal evidence). Those advocating for the .20's will talk of expansion or fragmentation. Those who advocate the .30's usually don't bother to discuss either one. It's the last bit that has me intrigued.

A 7.62x51 or .30-06 bullet is only .084" larger in diameter than a 5.56 bullet. Worst case if both bullets simply "ice-pick" straight through the target that extra .084" larger permanent wound cavity isn't going to do a whole heck of lot more. Obviously this minute difference in diameter isn't what gives the .30 rounds their reputation of being a better caliber on the battlefield. If we take a look at expansion, that's a no go for either caliber in FMJ. That leaves yaw and fragmentation.

Most .30 FMJ bullets will yaw, but don't fragment. How fast the yaw begins is what creates an issue. Most .30 FMJ rounds, begin to yaw well after the initial entry. 7.62x39 is famous for this, causing in general through and through wounds with little beyond a circular hole, most of the time. There are a few variants, produced in I believe Yugoslavia, that yaw much earlier and consequently would be far more lethal than other 7.62x39 FMJ rounds. American .30 FMJ ammo all appears to yaw very late, and as such would seem to produce a lot of through and through injuries. Additionally American .30 FMJ ammo tends to have a heavy jacket, which would contraindicate fragmentation. The .20's on the other hand yaw early, and at least the American variations fragments some of the time.

The only other factor I can see is that a .30 bullet tends to be longer, which when rotating will create a larger permanent wound cavity. A .30 147gr bullet is approximately 1.120" long and the current M855 5.56 is .905 long. A difference of .215 or approximately 20 %. Is a less than 1/4" increase in wound track diameter the difference between a "man killer" and a "poodle shooter?"

So what is it that makes the 7.62 NATO and the venerable .30-06 such a superior combat cartridge in terms of lethality to the 5.56? Beyond the need to reach out and touch someone (often overstated) by what mechanism is the .30 FMJ bullet made superior t0 the 5.56?

I'm asking this in all seriousness due to often repeated mantra of .308 being a better caliber for social work. Now I'll certainly agree that once we get out of military FMJ rounds, that .30 caliber bullet selection is more lethal than a comparable loading in .223; however the question is regarding military FMJ rounds.

-Jenrick

 

[briansmithwins]

For FMJ there is a pretty good body of work on terminal ballistics that indicates that .30 cal FMJ isn't particularly good because it has too much stability. There are exceptions, like the Mark 7 .303 Brit with aluminum or paper tips, which yaw early and violently.

In general, as long as 556 is moving fast enough to fragment and/or yaw, it's very effective, for FMJ.

BSW

 

[smithman 10]

.30 fmj

Could it be that .30 FMJ at 147 grains for 7.62 x 51 and 150 grains for .30-06 weighs almost three times as much as 5.56 FMJ? At least the 55 grain edition?

I'm no ballistics expert but when I read the foot pounds of energy on any box of .30-06 it looks a little more impressive than .223 or 5.56.

 

[Jackal]

Throw a pebble at someone. Now throw a brick at them. Nuff said.

 

[rbernie]

7.62x51 or .30-06 bullet is only .084" larger in diameter than a 5.56 bullet

I would suggest that computing this as a difference in frontal area is a more useful perspective.

Specific to your premise - I don't think that anyone suggests that .308 wound tracks are dramatically different than .224 wound tracks, absent bullet upset. The reason that 308 is considered a more potent fighting round is because it's more likely to reach the target than a lighter, more easily disturbed bullet.

 

[HammsBeer]

Leaving bullet yaw out of it, the larger mass of the .30 probably retains it's velocity through tissue better than a 5.56, thus creating a larger temporary or permanent wound cavity. A .30 is also better able to defeat light cover to reach the target, and will generally be more stable over a longer distance. If it does yaw, it's larger size and weight will push out a larger cavity.

On the other hand, if the 5.56 is travelling at fragmentation velocity, especially a lighter FMJ such as 55 grain M193, it will yaw and frag very quickly in the relatively small body area of a human, creating a disproportionately larger wound cavity for it's size. Bullet design and velocity are crucial for an effective 5.56. Out of a 20" AR you could expect to retain frag velocity out to over 220 yards, but from the 14.5" M4 it drops to about 90 yards. The main advantages of 5.56 is disproportionate wounding within frag velocity, the much lighter weight of the ammo, less recoil, and more control under full auto fire.

 

[jmr40]

The difference isn't all that much at normal ranges. The longer, heavier 30 cal bullets hold up better at longer ranges. And penetrate barriers better. But from a military or SD perspective that does not outweigh the negatives. For sniper rounds or designated marksman use I can see the 308 being an advantage. We made the right choice going with 5.56 for general use.

 

[BSA1]

I can't directly address the use of FMJ but during WWII the overwhelming bullet type that was used in the ETO (Europe) in 30.06 was armor piercing.

New recruits were trained in basic training not to shoot until they could see the enemy soldier. When they arrived in front line combat units the vets taught them to shoot through any cover a enemy soldier might be hiding behind using A.P. ammunition.

I lost my resource material for this info in a old computer crash.

I have never seen any military data for the Pacific but it would make sense to use A.P. against the Japanese whom used bunkers and caves a lot.

 

[Reloadron]

The difference isn't all that much at normal ranges. The longer, heavier 30 cal bullets hold up better at longer ranges. And penetrate barriers better. But from a military or SD perspective that does not outweigh the negatives. For sniper rounds or designated marksman use I can see the 308 being an advantage. We made the right choice going with 5.56 for general use.

I believe that pretty much covers it. For wartime and combat applications we went from the M14 (7.62 x 54 NATO) 308 Winchester to the M16 (5.56 x 45 NATO) 223 Winchester. Each rifle and cartridge has its good and bad points to weigh out. I guess it all depends on why you are buying or considering buying the rifle.

As I am currently pondering purchasing a M1A, my thoughts naturally turned to the ammunition it was designed to shoot.

Personally I shoot both, 223 and 308 and I shoot both from a variety of rifles. For long range target shooting (500 yards or greater) I like the 308 but my focus is target shooting, I no longer even hunt so taking game is no longer a consideration. I especially prefer the 308 with a cross wind. I don't care about the economics as I can load and shoot 308 just as easily as 223. For target out to 500 yards I like the little 223 rounds using between 70 and 80 grain bullets from a 1:7 barrel twist. My bolt 223 is a 1:12 twist so up close out to 200 or 300 yards I like the 55 grain bullets.

So what it comes down to is your intended application for a rifle and which rifle will suit your needs best. Planning on going into battle?

Ron

 

[bfoosh006]

A .308 bullet will out penetrate a .224 , 9 times out of 10.... and still f' up the person behind said cover.

Also a stock .30 cal 150 gr FMJ has a BC of .398ish v. a .224 55gr FMJ of .243ish..... so the .30 cal will fight the wind drift much better then a .224....

That is where the .30 cal is better then a .224 is coming from.

Otherwise in the real modern world... a .224 can do an awful lot.

Now if you switch to modern Softpoints / polymer tipped.... the .308 kicks the .224's ass.... abeit with considerably more recoil.

More Recoil means longer time to reacquire sight picture.

 

[Jenrick]

I agree with everyone who has posted above that different rounds do different things. I also agree that within it's velocity range the 5.56 FMJ can be a tremendously effective round. My question I guess in short is: Why is there no real evidence of anyone asking for a different cartridge in WW2 or Korea? As far as I ever no one in the military establishment had any question of the lethality of the .30 caliber bullet, even though in FMJ it's not a particularly stellar performer compared to what we would want a modern bullet do to. Why was this?

Okay so we if check frontal area, rather than strict diameter of two round: .308~.075 sq/in; .223~.039 sq/in or approximately 52% for the .30 head on. If we look at a completely sidewise bullet (and we'll just use a rectangle to make it simple) we get .308~0.345 sq/in; .223~0.203 sq/in or approximately 60% greater surface area for the .30. Interesting. A 50%-60% increase in surface area to cut a permanent wound cavity is decent jump in total tissue destroyed.

As far as penetration goes, no question a black tip AP round from either a .30-06 or .308 turns most things into concealment real fast. However I imagine that it probably is even worse about yaw then a regular FMJ round, so it's pretty much be guaranteed to ice pick through.

-Jenrick

 

[Malamute]

As I am currently pondering purchasing a M1A, my thoughts naturally turned to the ammunition it was designed to shoot

If its an academic exercise, ok. If youre seriously considering using FMJ ammo for defensive use, my first question would be "why" when theres vastly better ammo for both calibers easily available.

The difference is pretty academic at this point, the decision was made long ago, and the ammo for 5.56 had steadily improved even in the military, with Mk 318 and Mk 262.

 

[Reloadron]

As far as I ever no one in the military establishment had any question of the lethality of the .30 caliber bullet, even though in FMJ it's not a particularly stellar performer compared to what we would want a modern bullet do to. Why was this?

FMJ works and when considering what military ammunition must do under what conditions the use of FMJ bullets makes sense. Military rifles are not match target rifles, they are designed to function under a given set of harsh conditions. FMJ bullets or "ball" ammunition is a small-arms projectile consisting of a soft core (often lead) encased in a shell of harder metal, such as gilding metal, cupronickel, or less commonly a steel alloy. That definition from the Wiki but I am sure you get the idea. The use of full metal jacketing in military ammunition came about because of the need for improved feeding characteristics in small arms using internal mechanical manipulation of the cartridge to chamber rounds as opposed to externally hand-reloading single-shot firearms. The harder gilding was less prone to deformation than softer exposed lead, which improved feeding. It is often thought that military use of FMJ ammunition was the result of The Hague Convention of 1899, Declaration III, prohibiting the use in international warfare of bullets that easily expand or flatten in the body, but this only addresses that projectiles must not be designed to flatten or expand, not that they be jacketed. Jacketed bullets had been in use since at least 1882. Keep in mind that soft or hollow point rifle ammunition is more susceptible to abuse and also feeding problems that plain Jane FMJ.

As to calibers? The US adopted the 1906 Springfield to replace the 1903 Springfield in 1906. The original 03 Springfield cartridge replaced the 30-40 Craig which replaced the Government 45-70 with the 30-40 Craig being the first smokeless powder cartridge. Prior to WWII considerable thought went into replacing the 30-06 Springfield. The 276 Pederson was one possible. Unfortunately WWII came along quickly and it was decided to stay with the 30-06 which we had millions of rounds of and was usable in our infantry rifles as well as light machine guns.

I am not a cartridge buff but we have some members who can likely very well answer your question regarding change. Change was very much sought and I can tell you such decisions are not all that simple as politics more often than not drives the winds of change.

Ron

 

[35 Whelen]

Yaw this, tumble that, fragment, blah, blah, blah. Had you rather have a knitting needle (.22 caliber bullet) or a 5/16" rod (.30 caliber bullet)shoved through your chest?
If you were faced with a hoard of bad guys coming at you, would you rather have a .22 caliber rifle and hope that little FMJ bullet yawed, tumbled, and did all it's pixie dust little magic tricks, or use a larger caliber that will never make a hole smaller than .30"?
As an individual who has killed lots of big game with .22 calibers and .30 calibers, I can tell you without hesitation which is better every single time. Fact is, if I were going hunting and could choose between the perfect .22 caliber bullet of any type and a .30 caliber FMJ, I'd take the .30 any day. Penetration trumps everything else.

35W


35W

 

[Jenrick]

Malamute: Yes a purely academic question. I know what I'd stoke any of my rifles with for social purpose, and it's not FMJ.

Reloadron: My question is WHY the "common fighting man" felt so strongly about transitioning to the .223. The whole "poodle shooter" "varmint" cartridge thing. Was it just a matter of institutional inertia and group think, or is there an actual legitimate reason that .30 FMJ is better?

Yaw this, tumble that, fragment, blah, blah, blah. Had you rather have a knitting needle (.22 caliber bullet) or a 5/16" rod (.30 caliber bullet)shoved through your chest?
If you were faced with a hoard of bad guys coming at you, would you rather have a .22 caliber rifle and hope that little FMJ bullet yawed, tumbled, and did all it's pixie dust little magic tricks, or use a larger caliber that will never make a hole smaller than .30"?
As an individual who has killed lots of big game with .22 calibers and .30 calibers, I can tell you without hesitation which is better every single time. Fact is, if I were going hunting and could choose between the perfect .22 caliber bullet of any type and a .30 caliber FMJ, I'd take the .30 any day. Penetration trumps everything else.

You kind of made my point here. There is a VERY strong feeling out among a large group of folks that firmly believe that a .30 caliber FMJ is far better between a .20 caliber FMJ. My question is WHY? There is nothing about a .30 ball round that is magical. Is it just the approximately 60% larger permanent wound channel (which is still minimal compared to an expanding or fragmenting .223 round, or even a good 9mm JHP)?

-Jenrick

 

[Panzerschwein]

I use a PTR-91 for home defense loaded with Hornady TAP Urban loads, 110 grain hollow points that expand and fragment violently in a human body but don't have as much penetration through walls as standard .308. In fact, the penetration through obstacles is only about as high as the various .223/5.56mm hollow points offerings, but the wound potential is far greater.

Works for me. YMMV.

 

[35 Whelen]

My question is WHY? -Jenrick

Because the .30 caliber bullet is larger. Period.

35W

 

[Swampman]

A 7.62mm fmj bullet is not inherently less prone to fragmentation than a 5.56mm fmj bullet.

The thin cupronickel clad steel jackets used in German 7.62x51 rounds made the bullets much more fragile and prone to fragmentation in soft tissue than US gilding metal jacketed bullets.

The US gilding metal clad, steel jacketed, 7.62mm M-80 ball bullets are also more prone to fragmentation than straight gilding metal jacketed M-80 rounds, though not nearly as much so as the German stuff.

US M-193, 5.56x45mm ball is better at turning its energy into soft tissue damage at short ranges than US M-80, 7.62x51mm ball is, that's it.
It all comes down to bullet design.

British .303 Mark VII ball was more unstable and deadly when it hit soft tissue than US 30-06, M2 ball or German 7.92x57mm, even though the cartridge itself put out a lot less energy.

The .303 wasn't a better cartridge, its Mk VII bullet was simply better designed for destabilising quickly when it hit soft tissue, thus causing more damage.

A competent designer could easily make a 147 grain 7.62x51 fmj bullet that would fragment as readily as M-193 ball, especially if the M-193 was being fired out of a 14.5 inch barrel.

 

[The Big D]

Thus far no one seems to have mentioned the issue of the stretch cavity. In lightly built targets like humans the wounding mechanism of a fast moving bullet (>1500 ft/s or so) is largely the permanent and temporary stretch cavity. That cavity is roughly proportional to the kinetic energy of the bullet on impact (stretching tissue is the first place the energy goes). .308 has more than twice the energy at the muzzle that .223 does, and will still have about as much at 500y at .223 does at the muzzle. None of this requires the bullet to tumble/yaw, fragment, or do anything other than pass through tissue at sufficient speed.

 

[The Alaskan]

Lot of good responses, some of them pretty funny, but true.

As a die hard 30-06 fanatic and M1 Garand owner, anything I can add is obviously biased, however, i would suggest that the OP (Jenrick) is doing too much math. Math kills, but not like a bullet.

I suspect 30 cal shooters don't discuss "fragmentation, expansion, yaw" etc et because it's not terribly relevant. You said you're looking at buying an M1A. That tells me (perhaps incorrectly) that you're looking for a "battle rifle." (That's what my prepper friends call 'em.) So we need not discuss "ethical hunting bullets" etc.

The main reason fro the 30 cal popularity is straight out penetration. 30-06 ball ammo will blow through a lot more cover than those AR15 pop guns. (Comparatively speaking, of course.) Add to that, you get the ability to effectively hit target out past the AR15's maximum effective range of 550 meters. At least that's the number they made me memorize in the Army.) Trouble is, you pretty much never get an opportunity to use that long range in battle-historically speaking.

One other thing to consider, militaries use the FMJ in large part due to the Geneva (or Hague I forget which) convention that requires it. In another part, the FMJ is "more humane" and more likely to wound a soldier, which, in theory, actually pulls 3 soldiers out of the line. (1 wounded, and two to carry him back.) Obviously, that theory hasn't held true in a few decades.

 

[The Alaskan]

One last parting comment before I retire for the evening.

I know that if I hit someone with a 30 cal bullet, he's going down. You can talk about terminal ballistics all you want, and, most assuredly, those remarks have some validity, but the 30-06 ball bullet served this country well for half a century and through two world wars and a smaller war (Korea). There are literally MILLIONS of dead soldiers lying in battlefield graves all over the globe that will attest to the 30 cal's efficacy. It's kind of hard to argue with that kind of success-with or without a slide rule.

 

[C-grunt]

Obviously the 7.62 Nato is more powerful than the 5.56. That being said its more powerful (read more recoil) than needed in combat for the average rifleman.

That being said there is no guarantee to put a man down with a 30 caliber. Some dudes just dont die. If I had a hoard of guys after me id much much much have the lower recoil, faster follow up shots, and more ammo per magazine of the 5.56 over 7.62 Nato.

Even when M855 doesnt fragment it does not act just like a 22 lr. Ive seen wounds by both (with M855 outside of "fragmentation range") and they are not the same. That would e like saying a 90 grain 380 at 800 FPS and a 158 grn 357 at 1600 FPS are the same.

So in short..... 7.62 Nato does indeed outperform 5.56 but it does not make up for a rifleman's short comings. In realistic combat ranges they both perform well.

 

[ABTOMAT]

I have a 1965 Shooter's Bible with an article comparing the various replacements to the (then-hated and not revered as today) M14. The final line of the article seems appropriate for these threads:

"It's possible the debate of 7.62 NATO and .223 with always continue."

 

[HammsBeer]

Of course .30 cal is more potent than 5.56, it's like the rifle equivalent of 9 vs 45. Then 7.62x39 is like throwing .40 s&w into the argument. Pick your poison and learn to use it effectively. Ammo costs, recoil, weight of rifle and ammo, I'll choose the 5.56.

 

[DaisyCutter]

A 7.62x51 or .30-06 bullet is only .084" larger in diameter than a 5.56 bullet.

Diameter is only one dimension. Multiply the difference by 3.14 or π to get a better perspective in terms of circumference... Or square the radius and then multiply by 3.14 for the area. The difference grows dramatically, and you're only still in the 2-dimensional world. You gotta multiply by the cube (^3) before you get a real appreciation why it would feel different in the real world.

The 30 caliber is substantially larger, generally carries about double the energy, and causes far greater damage based upon a long history of empirical data.

Not to mention one of Newton's Laws regarding an equal and opposite reaction. The recoil difference between a 30-06 and a 223 should be a clear indicator of each projectile's felt "effectivity" on the receiving end.