Yaw for .223

[essohbe]

Another thread got me wondering if anyone knows:

How fast does a .223 (maybe 55gr-ish) round have to go to have enough velocity to yaw on impact like a 5.45x39 round?

(What about a 5.56x45? It would be different since it's longer than the .223?)

[c_jackson]

From my understanding, anything above 1500 fps. At that point, gravity begins to take over and trajectory begins to drop, causing a tumble when the round impacts. It also depends on the angle of entry. The source I'm using is a member of a US Army ordnance depot in Anniston AL. I usually get ahold of him whenever questions like this one come up. Interesting query, I like the ones that make me "look it up"!

[brian923]

.223 and the 5.56 cartridge are in essence the same thing. Differances between the two being brass and cartridge pressure. The projectiles can differ in length, as what I think your reffering to (62 grain is longer than 55 grain and 75 grain longer than 62 grain). As to yaw, my beliefs are that there's really not enough time for the bullet to yaw inside the human body. A 62 grain bullet fired out of an M4 travels at around 26-2700 fps. At 100 yards, probably around 24-2500 fps. The human body is around 10" thick. 10" is covered by said bullet offly quick. Add to the point that fMJ are not ment to release energy into the target. FMJ's "tunnel" straight through soft targets. Now, when they hit bone or body armore, the will deflect, but I wouldn't call it "yawwing" or "tumbling", but that's just my opinion. I have never personaly done any extensive study on this subject. Brian.

[essohbe]

...anything above 1500 fps.

Interesting. Maybe the ordinance depot guy could try it out with different barrel lengths and bullet weights for kicks and giggles.

...The projectiles can differ in length, as what I think your reffering to...

Yes.

A 62 grain bullet fired out of an M4 travels at around 26-2700 fps. At 100 yards, probably around 24-2500 fps.

What if you increased the barrel length or had faster twist rate, would that affect the velocity or just give stabilization for range?

[Swampghost]

Yaw stabilizes on a 5.65 round at about 20 M. from the muzzle. The 5.65 was also originally developed as a 200 M. round. Given the velocity (about 3,000 FPS) and the air pressure wave created in front of it, the actual projectile should not contact flesh at all on an unprotected human.

The total destabilization/yaw factor myth MIGHT happen if you were drilling a Cape Buffalo from stem to stern with a 5.65 AND hit some bone.

The commonly accepted stuff (cr-p), tumbling bullets doesn't hold water. They can still make you very dead though.

[kd7sgm]

the actual projectile should not contact flesh at all on an unprotected human

Swampghost,
Are you sayng that the bullet will not touch flesh due to the pressure wave in front of it? please elaborate on this as I have not heard this before but it sounds very interesting. Does this occur at specific velocities?

[Bartholomew Roberts]

All spitzer type bullets will yaw in a mostly liquid medium like flesh eventually. They yaw because the pointed spitzer fron weighs less than the base. The lighter front sheds energy faster than the heavier base and eventually the rounds flips over base forward. Where they yaw depends is affected a great deal by the bullet design.

M193 55gr will yaw after travelling about 4-5" in ballistics gel. Hornady 75gr yaws almost immediately on impact. Some lots of M855 may travel as much as 7-9" before yawing.

The big place speed comes into play with 5.56 is in determining whether the round breaks apart and fragments when it does yaw. For M193, this velocity is around 2,700fps; but it can be higher or lower depending on the bullet design again.

Here are some other good TFL threads on the subject:
http://thefiringline.com/forums/showthread.php?t=342468
http://thefiringline.com/forums/showthread.php?t=394914
http://thefiringline.com/forums/showthread.php?t=405881

[stubbicatt]

Guys. Read up on Fackler's studies on military projectiles on flesh. Some rounds are designed to yaw, which is the old 303 Brit and 5.45 Russian round's design.

I may be wrong on this but the theory on 5.56 wounding is fragmentation rather than yaw.

Now the recent (for 556) innovation of the 77 grain bullet may have changed over to yaw, again I'm not certain.

[rickyrick]

I was always under the impression that the bullet was notorious for fragmentation.

While in the Army we were taught that bullets 'purposely' designed to yaw were Illegal

[woodguru]

Read up on twist rates for .223's. There is enough weight differentials between the lighter bullets and heavier ones that there is also a range of twist rates that stabilize different weights in an optimum fashion. Twists have been made in quite an extreme range, I think from 1:7 to about 1:14. Yaw or bullet instability is possible if that's what you are looking for, for most bullet instability goes against what you are looking for with accuracy. I was and will be researching this because I want a .243 AR style rifle that shoots very accurate and stable out to 600 yards, I'll get the right twist and load accordingly.

Twist rate is actually a very interesting factor, certain good rifle cartridges have had their potential popularity sabotaged because rifle manufacturers chose the wrong twist rate for production rifles which then impaired performance for logical uses of the cartridge.

This subject actually goes into the question raised here on "rifle or cartridge" which makes the most difference. The twist rate a manufacturer decides to use makes a huge difference in how the cartridge will perform in different weights.

[essohbe]

Allot of good info there, thanks for the links.

It seems to be that a .223/5.56x45 fired from a proper barrel will produce more permanent tissue dissrupttion through fragmentation vs a 5.45x39 that produces less permanent damage but more temporary tissue damage through yaw.

Okey. Me a bit slow for mathing, so you help me yuh?

Q: Since it is my current circumstance I am in the market for a Saiga, which typically have a 1:9 -1:10 twist rate (for .223), what would I need for a barrel length in said twist rate to get matched or better wound ballistic performance from a .223/5.56x45 than the soviet 5.45x39?

[Bartholomew Roberts]

Twist rate doesn't really affect terminal ballistics beyond its affect on the basic accuracy of the round. People are under the mistaken impression that a round that is more unstable in air will somehow cause more damage; but flesh/liquid is so much more dense than air, that you would need a faster twist rate than any rifle ever made in order to spin stabilize a round in the much denser medium.

The only thing the twist rate will do is stop you from being able to accurately launch the longer bullets. As far as surpassing 5.45x39 - bullet design is more important than caliber or twist rate. 5.56mm M193 can outperform 7.62x51 M80 ball in wound channel size - it is all about the bullet design.

[Trigger Finger]

brian923"As to yaw, my beliefs are that there's really not enough time for the bullet to yaw inside the human body."

Just speaking out of experience, when you shoot at someone or something behind a bush and you see a perfect 22 caliber hole in a leaf at the front of the bush and then about 8 or 10 inches toward the target and another leaf has a perfect "key hole" in it like the bullet was flipping after penetrating the first leaf, this leads me to think that the bullet is Yawing or flipping after the first very minor impact with a leaf. I was told that this can occur after a few inches of penetration in a person.
And almost every caliber can begin to flip after a miner impact with something before the target. A 50 BMG sometimes does the same thing!!!!

[essohbe]

Yea I see, so all I'd get out of the longer barrel really would be range and stability for the heavier rounds.

[brian923]

Longer barrel-higher velocity.
Twist rate determines accuracy in regaurds to bullet weight. Slower twist rates typicaly used for heavier bullets, faster twist rates for lighter bullets. Projectile design plays the most significant role. Fragmenting bullets cannot ne compared to FMJ's. They act completly different. As to the leaf sinario, I don't see how a leaf can upset a bullet traveling that fast. I have shot through multiple pieces of paper set up a varying distances and have gotten straight bullet holes in both sheets. I have shot v-max bullets through small logs and seen explosive exit holes. I have shot that same v-max round at drum cymbols and got paper punch like holes when the bullets should have not even penitrated the hard metal surface!!

[Bartholomew Roberts]

Originally Posted by brian923

Slower twist rates typicaly used for heavier bullets, faster twist rates for lighter bullets.

You've got that backwards. A faster twist is necessary for longer bullets (which are usually, though not always heavier). A slower twist will stabilize shorter bullets. For some examples, the 62gr M855 tracer is long enough that it needs the 1:7 twist to stabilize it, even though your typical 62gr plinking ammo will stabilize just fine in a 1:9 barrel.

Fragmenting bullets cannot ne compared to FMJ's. They act completly different.

Actually, many modern 5.56mm FMJs will yaw and fragment when they strike flesh. You can see examples of this in ballistics gel in the links I gave earlier in this thread.

As to yaw, my beliefs are that there's really not enough time for the bullet to yaw inside the human body.

Again, see the links above. Bullets yawing inside people is a well-documented phenomenon for both rifle and pistol bullets.

[brian923]

Want to apoligize for my earlier post were I got the twist rates ( slow and fast) reversed. I was tierd and I didn't mean to confuse anyone.

[Trigger Finger]

brian923. A bullet can and is affected by leafs, twigs and brush prior to hitting the target as evidenced by these statements!

"Jack O'Connor, in his Gun Book wrote about the results of such a test that he spent several afternoons conducting with a variety of calibers and bullet weights. O'Connor shot at a 3' by 4' outline of a deer through a heavy screen of natural brush. His results indicated several things. One was that, as logic suggests, the farther behind the brush the target was placed, the safer it was. At 6' the "deer" was liable to be hit; at 20' the "deer" was pretty safe.

O'Connor tested a variety of calibers from the .220 Swift to the .375 H&H Magnum, including the standard one ounce 12 gauge shotgun slug. This latter projectile proved to the best brush-bucker of them all, as it is stabilized by its weight forward design rather than by spin. Even the 300 grain Silvertip bullet fired from the .375 Magnum showed considerable deflection in O'Connor's testing. The .35 Remington's 200 grain RN bullet often found the target, but frequently hit sideways.

The worst caliber for penetrating brush was the .220 Swift loaded with a 50 grain Spire Point bullet. It almost never made it through the brush intact. (No surprise, as this bullet is designed to break-up against light resistance.)

Fairly light (for their caliber) high velocity bullets such as the 87 grain .250-3000, 100 grain .257 Roberts, 130 grain .270 Winchester, and 150 grain .30-06 spitzers also faired poorly in O'Connor's brush tests. The 100 grain .250 bullet was better than the 87 grain bullet, but still not very good at getting through the brush. The 117 grain RN .257, 150 grain RN .270, and 180 grain RN .30-06 bullets all gave O'Connor a much improved chance of hitting the target in their respective calibers."

You said "As to the leaf sinario, I don't see how a leaf can upset a bullet traveling that fast. I have shot through multiple pieces of paper set up a varying distances and have gotten straight bullet holes in both sheets. I have shot v-max bullets through small logs and seen explosive exit holes."

An explosive exit hole could be a sign of a tumbling bullet!!

http://chuckhawks.com/woods_rifles.html

[NWPilgrim]

Mr Roberts statements are exactly what I remember as well. 2700fps is needed for a 55 gr FMJ bullet to have max yaw and fragmentation. If you have a 16" barrel you can't get this reliably beyond 200 yds. If you are shooting game/varmints or enemy beyond 200 yds you want a bullet with a better design than 55 gr FMJ.

BTW, some postings seem to interpret the question as to yawing in mid-flight. I think the OP means yaw within the target body. fragmentation mainly occurs with the 55 gr FMJ due to the yaw. As it turns broadside the fluid pressure breaks the bullet in half and thus weakened it shatters further.

Our military are politically restricted to use some form of FMJ or OTM (not intended to expand but for accuracy) but as civilians we can choose from many bullet designed that have better terminal effect over a broader range of velocities and ranges. Do a Google search for "barrier blind" and .223 or whatever. Nosler partition 60 gr, and various bonded bullets have some of the best overall effect under a variety of conditions.

[c_jackson]

I asked again, with a little more depth provided. The reply came back the same "Anything moving above 1500 fps." Explanation given, despite type of rifle, barrel or load, gravity and drag behave the same way on all loads given once they reach a point in time and space where flat trajectory degrades. Simple physics takes over and load weight becomes a non-issue, the round starts to run out of kinetic energy. Depending on angle to impact and the density/resistance of the target impacted, the round will behave erractically and one cannot predict the path of the bullet as it loses momentum. As the speed of the projectile decreases, the bullet will impact in a falling curve and is more likely to tumble end over end once it hits. Yaw is more likely to happen as the round is at higher speeds, thus the "anything over 1500 fps" estimation. I post this response with the full admission, I am not a ballistics expert, I merely asked somebody whom was. Bear in mind, this is an estimation. Many factors play into this, as I was told, it was suggested this might better be taken up with "Mythbusters" to provide a concrete answer satisfactory to all. Sorry guys, I'm not being sarcastic, I'm only relaying what I was told.

Apologies if I've offended anyone,
C. Jackson