5.56 -twist,wieght, and effectiveness.


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Tokugawa
March 12, 2006, 06:29 PM
The debate about the effectiveness of the 5.56 has been going on for years, lately there has been some talk from Iraq about poor performance. I am interested hearing from those who have actually used the weapon there, and have a question - As I understand it, the 5.56 was originally 55gns, and used a twist of 1/12, resulting in a round that was marginally stabilized and would tumble violently on impact. Now the military has gone to a 62gn bullet, and a 1/8 twist (or thereabouts) to stabilize it, primarily to enhance long range effectiveness. Does this have the result of making the bullet so stable that it no longer tumbles on impact, resulting less wounding potential?

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TMM
March 12, 2006, 06:39 PM
i believe it is now a 1/9 twist.

i was talking to an army buddy, and he mentioned how, atleast in close ranges, the bullet is going to fast that it dosn't do anything nasty except make a 5.56mm hole. don't know about farther ranges. i do know, however, that he hates the .223 round. heh...

~tmm

Chris Rhines
March 12, 2006, 06:47 PM
All military M16s and M4s use a 1:7" twist barrel. The purpose of the unusually rapid twist rate supposedly has to do with stabilizing the L110/M856 tracer round issued by the military - it's very long for its weight and takes a very fast twist to stabilize.

Barrel twist rate has no effect at all on terminal performance.

- Chris

SB88LX
March 12, 2006, 07:16 PM
I forget where, but somewhere online someone did the math to see what kind of rpms would be necessary to stabilize a bullet for a flight through flesh. Standard rpm for the 5.56 was somewhere between 100,000 and 200,000 to be stable through air (I forget), and it would take something like 98,000,000,000 rpms to stabilize a bullet in flesh. The faster twist rate accounted for delaying bullet tumbling for something ridiculously irrelevant, like .00001 of an inch.

gripper
March 12, 2006, 07:28 PM
At least part of the problem is that the M193 and M855 ball loadings largely rely on a high velocity at the muzzle to have the wounding ballistics you mention( tmbling,cannelure separations/frag,disruption of soft tissue).Both were developed around a 20 inch barrel (M16A1 and M16A2).Add in the shorter barrels of the M4 carbines ,coupled with engagements that often take place beyond the range where the short barrel/stabilized 62 grain bullet combo begins to shed velocity,and YES,you often produce less than perfect results.Many times people will(and have) soaked up numerous non survivable wounds,running on adrenaline and remaining effective for a suprising ammount of time.There has been efforts,both with the 77 and 75 grain ammo usage in certain units,as well as developement of other calibers(6.8,etc) , not to mention the re-issuance of the M14.In the end ,you still have to hit the guy;that said,while I don't want to step in front of a 5.56,I prefer other calibers.

Ares45
March 12, 2006, 07:39 PM
tumble violently on impact.

That's the whole idea.

The tigher twist rate was needed to stabilize larger grain tracer rounds.

Too Much 5.56 Info (http://www.ammo-oracle.com/body.htm)

rangerruck
March 13, 2006, 05:44 AM
check this:
http://www.ammo-oracle.com/body.htm#whattwist
this helped me out quite a bit.

Turk
March 13, 2006, 08:08 AM
Gripper I couldn't said it any better.

TMM your post: """"""i was talking to an army buddy, and he mentioned how, at least in close ranges, the bullet is going to fast that it dosn't do anything nasty except make a 5.56mm hole. don't know about farther ranges. i do know, however, that he hates the .223 round. heh..."""""

This is the complete opposite. A FMJ bullet can be just as destructive as a spire or hollow point IF driven at a high velocity. Compare a 308 150 gr. SP and a 300 Win. Magnum 150 gr. SP which one is more destructive besides having longer range?

In urban fighting (close up and dirty in the buildings) even the M-4 should be effective. One thing to keep in mind about the combat effectiveness of any rifle etc. is if first hand or a buddy story (you know my sisters boy friends uncles brother told me this)? Also what is the persons MOS? My personal choice is the M-193 ball with either 1-12 or 1-14” 20” barrel.

Also when is big enough. Many years ago I seen a guy hit with a MaDuce round in the upper thigh and he was still able to continue the fight?

Turk

Remember to pray for our troops.

ROAshooter
March 13, 2006, 08:34 AM
355sig should be a long shortly and inform you all of everything you ever wanted to know about 5.56/223.....

Byron
March 13, 2006, 10:46 AM
My experience with he M193 round was as a 20 year old infantryman in Vietnam in 68-69. I found the round to be very lethal. I have talked with some returning infantrymen from Iraq. The M855 has some lethality problems.The 77's seemed to do well. Byron

MechAg94
March 13, 2006, 01:10 PM
+1 Turk

I have no personal experience with shooting people with 5.56, but I have heard numerous accounts both for and against. The problem with ancedotal accounts is there is no way to gauge accuracy/shot placement or the circumstances for each individual account. The guy could have missed the bad guy completely for all I know yet still think he made hits and the bad guy kept fighting. There is no way for me or others to argue or judge the point.

Caliber is not everything. As Turk implied, if all our soldiers were issued .50 Caliber BMG rifles, there would still be stories floating around about people who were hit and kept going.

There are several other reasons why the military will stick with 5.56. Pure effectiveness on bad guys is probably a small part of that decision anyway.

Don't Tread On Me
March 13, 2006, 01:59 PM
The debate about the effectiveness of the 5.56 has been going on for years, lately there has been some talk from Iraq about poor performance.

We've been using it for 40 years. You have to come to believe that our military is not *that* hell bent on insisting our soldiers use an ineffective cartridge for this long of a time period. Remember, it isn't the military that is looking to save money or to compromise, it is usually the government. If the 5.56 was so terrible, the military would have been nagging and lobbying very hard since the 1960's to replace it. They haven't. Must be doing some good. I know this isn't logic for determining effectiveness, but let's be reasonable here.


I am interested hearing from those who have actually used the weapon there, and have a question

That's definately not me. However, the questions you're asking aren't answered by combat veteran experience. They are better answered by reading the reports and journals published by doctors and others who've done ballistics testing in a scientific manner. Most of what you hear or read on the net comes from these papers.


As I understand it, the 5.56 was originally 55gns, and used a twist of 1/12, resulting in a round that was marginally stabilized and would tumble violently on impact.

Nope. Twist has nothing to do with tumbling on impact. Either a bullet is stabilized, or it is not. Tumbling is a factor of bullet shape/balance. If a bullet is thin, long and butt heavy...the mass at the rear is going to want to go forward after impact - hence the tumble.


Now the military has gone to a 62gn bullet, and a 1/8 twist (or thereabouts) to stabilize it,

1/7. Although 1/8 would have worked just fine, 1/7 was needed for shooting tracers. Longer the bullet in relation to its diameter, the faster the twist you need.

primarily to enhance long range effectiveness.

Not quite. The 62gr is actually less effective than the 55gr when it comes to fragmentation range. The idea behind the 62gr was to increase penetration of thin/mild armor at longer ranges.

Does this have the result of making the bullet so stable that it no longer tumbles on impact, resulting less wounding potential?


Nope. Now, maybe it might cause the "neck" of the wound channel to be longer, or make the bullet travel longer inside the body before it begins to tumble...I don't know. That is pure speculation on my part. Bottom line, there aren't enough RPM's on any 5.56 to keep it from tumbling after hitting. If there is a difference between a given bullet, like say a 62gr spinning 200,000rpm vs. 300,000 rpm..you'd have to shoot many gel blocks and then measure the neck of the wound channel. If there is a difference, I can't imagine it would be large enough to make any practical difference at all.

Onmilo
March 13, 2006, 03:10 PM
Heavy bullet, long range rifle, 1 in 8 twist.

Standard use, general purpose, use it for everything rifle, 1 in 9 twist.

Mostly varmints and maybe a few 62 grain bullets now and again, 1 in 10 twist.

40-45 grain bullets, a varmint killer and nothing but except for a few afternoons plinking at the range with some 55 grain surplus or Q-loads, 1 in 12 twist.

You decide what you are going to do most and go from there.

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