Knockdown Power vs. Accuracy?

[Guest Steelharpson]

So... I think we can all agree we have heard the stories of the accuracy of the 5.56mmx45mm but its' lack of "Knockdown" and then the 7.62mmx51mm... both standard NATO rounds. The 5.56 has proven its' capabilities of penetration, also the 7.62( .308) shows that between the 0-300 meters carries almost twice the kinetic energy as the 5.56 but looses accuracy after that distance. CQB fall under those distances. Personal opinions and experiences on that please haha. Either more rounds, less weight but less power or less rounds, more weight but more power. I have looked at also the 6.5 Grendel and 6.8 SPC rounds...suppose to be that happy median. However, are they as easy to come across as the 5.56 or the 7.62?

[Jonnin]

The 5.5 is not as accurate for as far as the 7.6 either -- its more easily messed up by wind, for one thing. A good 308 is more accurate than a 5.5, IMHO. Thats a bolt action though, not a AR. I dont have a lot of AR experience, but its not the cartridge. Energy isnt everything, momentum is just about as important, also IMHO.

Most things "gun" are about tradeoffs... you just have to choose what you want for your application. What exactly are you wanting to do with the gun? I dont know aobut you, but I need a good reason to be shooting at something 300+ yards away, apart for paper targets for fun. A person that far away either is good enough to have killed me already or I am *gone* from the area, not going to get into a sniper war no matter how much I think of my own marksmanship. And if I do get into it at that range for some unholy reason, I will use a bolt action with a massive scope, not a spray & pray or toy AR. (Now, if I had in hand a full auto AR for real, maybe..)

To answer it another way my "zombie" gun is just a 223, with a 2-7X scope & a laser sight for up close. That gets me to ~200 yards. Anything farther out is just not reasonable for anything I need to do, and if I did need that, I have a variety of bolts to fall back on.

[DaveTN]

First off for typing sake I will refer to the 5.56x45mm NATO as 223 and the 7.62x51mm NATO as 308. I am familiar with these rounds and I thoroughly understand that military and civilian versions are not the same. That being said….

You have used both haven’t you? I have a lot of experience with both the .223 and .308 and have both. I have never been impressed with the .223 and my opinion is that it is nowhere near being in the class of the .308 as a round capable of stopping the threat.

Unless I’m reading your statement wrong you are saying you think that the .308 loses accuracy beyond 300 yards. That just isn’t true. There is a reason your Marine Corps Snipers use the .308 instead of the .223. Also Bench rest shooters.

I have a DPMS .308 Panther and that is the combat rifle I would want. Even for close quarter combat. It is devastating, it fires a round that is capable of ending the threat, and it was a proven performer in a couple of wars.

The main complaint I hear is the weight of the ammo. I would think that now a day’s most of you have vehicles with you and the weight issue could be overcome. For us (Civilians and LEO’s) it’s not an issue.

I think it’s terrible that our government will not give our troops the tools they need to stay alive. Going to 9mm and .223 was a tragedy that has cost the lives of many American servicemen and women.

Thank you for your service and welcome to the forum.

[Guest 6.8 AR]

So... I think we can all agree we have heard the stories of the accuracy of the 5.56mmx45mm but its' lack of "Knockdown" and then the 7.62mmx51mm... both standard NATO rounds. The 5.56 has proven its' capabilities of penetration, also the 7.62( .308) shows that between the 0-300 meters carries almost twice the kinetic energy as the 5.56 but looses accuracy after that distance. CQB fall under those distances. Personal opinions and experiences on that please haha. Either more rounds, less weight but less power or less rounds, more weight but more power. I have looked at also the 6.5 Grendel and 6.8 SPC rounds...suppose to be that happy median. However, are they as easy to come across as the 5.56 or the 7.62?

I don't know about the Grendel's availability, but the 6.8 is easy to find. Ammo is becoming more available also.

[Dolomite_supafly]

The problem is not the 5.56 cartridge itself, it is what the military has tried to do to "improve" it that has ruined it. The 5.56 needs barrel length to be as effective as it can possibly be. The next problem is barrel twist, too much twist and the bullet overstabilizes which leads to even more problems. An over stabilized bullet that doesn't have enough velocity to come apart upon impact will not tumble and will only punch a neat little hole through the target. Even if it does tumble it will likely be through most of our enemies in the middle east by the time it does. Most males over there are concentration camp thin. An Afghan male that weighs more than 130 pounds is a big Afghan and most come in under 110 pounds. They are very, very thin and as such we need a round that will tumble or fragment within the first few inches in order to eb effective on these targets.

The military ruined the cartridge by increasing the twist and using heavier bullets. The heavier bullets require the velocity to be reduced this reduces the chance the bullet will disrupt on impact and the increased twist decreases the likelyhood of the bullet tumbling upon impact. Believe it or not but by taking the 5.56 and reducing the velocity to less than 2000 fps it will increase its penetration because the bullet no longer tumbles or disrupts on impact. This is the reason we are hearing of all the problems with it overseas. The military is trying to take a short to medium range caliber and turn it into a long range caliber.

Here are some interesting reads on the effectiveness of the 5.56:

Do not hot link this but copy and paste it into a new browser to open it:

http://stevespages.com/pdf/5_56mm_military_info.pdf

This is the penetration based on velocity:

http://stevespages.com/jpg/bestbullet.jpg

Again DO NOT HOTLINK. Open a fresh browser and copy the above URLS. The host has had issues with people hacking his erver so he has disabled a lot of differnt stuff including hot links.

The original design had it nearly perfect with a 12 twist barrel shooting 55 grain bullets. The twist was slow enough that it would tumble upon impact and the velocity was fast enough with the light bullets that is would disrupt upon impact as well. If the military would start using longer barrels with a slower twist and lighter bullets in the AR platforms there would be and increase in effectiveness on soft targets. The Marines have it right by using longer barrels and this is probably why you don't hear as many problems coming from their side of the house regarding the effectiveness of the 5.56 because ever FPS counts. The military needs to quit trying to make the 5.56 into something it will never be, a long range caliber.

The 5.56 is a wonderful caliber but is not a magical caliber that the military wants it to be. As long as you stay within is limitations and original design it performs very well. The 5.56x45 and the 7.62x51 are in two seperate classes. The 5.56 is not what I would consider a long range caliber while the 7.62x51 is. 7.62x51 is always going to be better than the 5.56 in actual performance but with everything else in life there is a trade off. For most the 5.56 is plenty. The 7.62x51 is more of a long range caliber or hard target caliber or at least more so than the 5.56.

If I were going to be using a short barreled gun I would not choose the 5.56. I would use any of the others you mentioned or even the 7.62x39. With a 10" barrel there even isn't enough velocity at the muzzle for the 62 grain bullets to tumble or fragment. If you must then I would definitely use a bullet that is designed to disrupt like any of the polymer tipped bullets like the TAP rounds.

Dolomite