Guess SCAR is a done deal.

[P. Beck]

Will"s right. Between the M4's 14.5" barrel and 1/7 twist, and the M855 round, you've got about 150 meters worth of gun, wound ballistics wise. Past that the M855 settles down into a nice stable trajectory through both air and tissue. I've seen failures to stop with M855 torso hits at >150 meters. I've never had that problem doing it my way.

7.62x51mm, 126 grains @ MV of 2950 fps vs. 5.56x45mm, 62 grains @ MV of 2750 fps. Do the math.

I treat Hajji like any other dangerous game. Big holes, all the way through, are better. Someone once asked a big game hunter in Africa why he used a .600 Nitro Express. "Because they don't make a .700 Nitro Express.", he answered.

I've been doing this for a while now and I'm still here. Either it works or I've been inordinately lucky.

 

[WillBrink]

Will"s right.

Well it had to happen some time! Reminds me on and old Buddhist riddle:

If a man is walking through the forest talking to himself, and there is no women to hear him talking, is he still wrong?

Between the M4's 14.5" barrel and 1/7 twist, and the M855 round, you've got about 150 meters worth of gun, wound ballistics wise. Past that the M855 settles down into a nice stable trajectory through both air and tissue. I've seen failures to stop with M855 torso hits at >150 meters. I've never had that problem doing it my way.

Did they ever change the twist rate? Most manufacturers offer 1/9 which is better for heavier bullets like m855 and you have companies like Black Hills etc making bullets that get the most out of the m4 1/9 configuration. My understanding is a few units were given "special" 1/8 models.

7.62x51mm, 126 grains @ MV of 2950 fps vs. 5.56x45mm, 62 grains @ MV of 2750 fps. Do the math.

I treat Hajji like any other dangerous game. Big holes, all the way through, are better. Someone once asked a big game hunter in Africa why he used a .600 Nitro Express. "Because they don't make a .700 Nitro Express.", he answered.

Or this story:

This was some time ago when a reporter did a human interest piece on the Texas Rangers. The reporter recognized the 1911 the Ranger was carrying anda asked him "Why do you carry a 45". The Ranger responded with, "They don't make a 46".

I've been doing this for a while now and I'm still here. Either it works or I've been inordinately lucky.

Or perhaps both. It's better to be lucky than good... ;)

 

[pardus]

“Shorter barreled assault rifles have a muzzle velocity below the critical level so rounds fired from these will not fragment and will produce reduced wounding and incapacitation. There is some evidence that these bullets will not tumble either, and behave like small calibre FMJ pistol rounds. Minimum barrel length for use with FMJ rounds seems to be 14.5". Tests show a 55gr M193 fired from a M4 with a 14.5" barrel has a muzzle velocity 2,850fps and fragments. The same round fired from a G36K with a 12.5" barrel has a muzzle velocity of 2,650fps and very little fragmentation. Note that the current issue M855 62gr round has a lower muzzle velocity than a M193. Range at which fragmentation will occur with either round from 14.5" barrels is probably less than 100m”

Very interesting, I did not know that, thank you.

 

[WillBrink]

Very interesting, I did not know that, thank you.

No problems. It's not a well known and talked about issue, though it probably should be. The M4 gives up a lot of its "stopping power" with that short barrel but changes in twist rate and bullet design can make up for it, but that's more in the LEO and civi stuff as the military has stuck with the 1/7 twist and standard ammo. Pehaps the SCAR design addresses that? Don't know.

The 5.56 doing approx 3000fps or better out of the old m16 is a nasty little bullet due to its fragmenting, which makes a big wound channel, but by design, it's very dependent on the velocity to do it's thing, where as the 7.62 is effective over a wider range of velocities and has real crsuhing power the 5.56 lacks.

 

[pardus]

Yeah, like I say I love the 7.62, Thats all I want to use.

 

[WillBrink]

Yeah, like I say I love the 7.62, Thats all I want to use.

Well there's having a head full of facts and figures (like yours truly) and there's actually going out into harms way and doing it, so use what you love ;)

 

[pardus]

OK Will and anyone else...

I'm currently looking at building a metric FN rifle, I have four barrel options, 21" (standard) 18", 17" & 16", I would like to know what difference the barrel length is going to make particularly with accuracy and ballistics (as noted with the M4).

Thanks.

No problems. It's not a well known and talked about issue, though it probably should be. The M4 gives up a lot of its "stopping power" with that short barrel but changes in twist rate and bullet design can make up for it, but that's more in the LEO and civi stuff as the military has stuck with the 1/7 twist and standard ammo. Perhaps the SCAR design addresses that? Don't know.

The 5.56 doing approx 3000fps or better out of the old m16 is a nasty little bullet due to its fragmenting, which makes a big wound channel, but by design, it's very dependent on the velocity to do it's thing, where as the 7.62 is effective over a wider range of velocities and has real crsuhing power the 5.56 lacks.

 

[rangerpsych]

The best place to be hit providing it doesnt take out a lung is the chest cavity, lots of room for expansion and a lack of tissue damage as one would find in a bullet to a muscle.

I would totally disagree.. regardless of the round, you stand a larger chance of impacting a bone and causing significant trauma due to the secondary fragmentation induced into the wound channel and surrounding tissue. Not to mention the fact that there's alot of significant organs there that are rather important for everything in your body to function... l

A extremity wound is easier to care for and deal with, and significantly more survivable than a round taken to the chest cavity (navel to neck, basically)

 

[WillBrink]

OK Will and anyone else...

I'm currently looking at building a metric FN rifle, I have four barrel options, 21" (standard) 18", 17" & 16", I would like to know what difference the barrel length is going to make particularly with accuracy and ballistics (as noted with the M4).

Thanks.

The question is a bit above my pay grade to be honest with you. The general rule of course is the longer barrels will give greater accuracy and velocity, but of course there are a zillion other variables to that, and of course the choice of barrel length depends very much on what you plan to use it for, eg, it’s mission specific.

I’m sure you can find the velocity charts for those different barrel lengths and make some choices from there. Actually, that link I put up above might have some of that info as it did for the 5.56.

Wish I had better info for you, but my interest/knowledge is more in the area of terminal ballistics vs gun designs. As mentioned however, the 7.62 terminal performance (which of course is not the same thing as accuracy) suffers less from shorter barrel lengths than the 5.56.

If I had to guess, I bet a nice balance between everything would be the 18", but that's really a guess on my part. Beyond that, you will have to take it to a pro. The two places I would check/post to on that would be the Terminal Ballistics section of the tactical Forums:

http://www.tacticalforums.com

Or, look at the 8-10 forums:

http://www.10-8forums.com

Those forums have some real smart people and wanna be types, BS artists, net gun experts, etc are not tolerated there.

Hope that helps.

 

[pardus]

I would totally disagree.. regardless of the round, you stand a larger chance of impacting a bone and causing significant trauma due to the secondary fragmentation induced into the wound channel and surrounding tissue. Not to mention the fact that there's alot of significant organs there that are rather important for everything in your body to function... l

A extremity wound is easier to care for and deal with, and significantly more survivable than a round taken to the chest cavity (navel to neck, basically)

Thats what I originally thought too, maybe the medics were bullshitting me.

 

[P. Beck]

Update:

Well, looks like our unit issue of the SCAR is on hold. Something about manufacturing delays. Best guess is that we'll get them next fall.

That's ok. I'll be over here in the corner. Cleaning my M14. Again.:)

 

[phridum]

I feel a little stupid now, having reposted basically all this information in my post in Will B.'s other thread...shrug...and I'm not changing it

I also think I might have misunderstood the question in that thread because why would he ask about something being covered in this thread? Hrmm...I'm'a go figure out.

 

[WillBrink]

I feel a little stupid now, having reposted basically all this information in my post in Will B.'s other thread...shrug...and I'm not changing it

I also think I might have misunderstood the question in that thread because why would he ask about something being covered in this thread? Hrmm...I'm'a go figure out.

I am not sure I am following what you are not following! ;)

 

[Pete031]

Overseas, we used 77 grain. It worked a lot better then the standard, however, I would not go any shorter then 14.5 inches for the Carbine.

 

[8'Duece]

Overseas, we used 77 grain. It worked a lot better then the standard, however, I would not go any shorter then 14.5 inches for the Carbine.

Actually the SEALs use the Mk262 77 grain from Black Hills in their CQBR rifle/Mk18 which is 10.5" barrels. (LMT UPPERS/Crane Lowers)

I don't know what kind of performance they get out of it, but they use it for their own reasons.

 

[WillBrink]

Overseas, we used 77 grain. It worked a lot better then the standard, however, I would not go any shorter then 14.5 inches for the Carbine.

What was the twist rate of the gun? My understanding is the 1:9 twist works best with the heavier bullets and manufacturers are making the m4 with 1:9 twist, at least for the civi markets. I have heard good things about the 77g out of the M4 length guns, but I don't have any data on it. Will have look around.

 

[pardus]

I would not go any shorter then 14.5 inches for the Carbine.

I think 16" is short enough due the the lack of velocity but WTF would I know? :uhh:

 

[WillBrink]

Actually the SEALs use the Mk262 77 grain from Black Hills in their CQBR rifle/Mk18 which is 10.5" barrels. (LMT UPPERS/Crane Lowers)

I don't know what kind of performance they get out of it, but they use it for their own reasons.

Here is a Colt Commando I was playing with via my buds at the regional tactical team and they use the Black Hills rnd also. Man I wub that evil little machine...The Colt is 11" or 10.5, I forget, but what's a half inch between friends? :eek:

 

[WillBrink]

I think 16" is short enough due the the lack of velocity but WTF would I know? :uhh:

Well there are the people who think about the shit, and the people who go and do the shit. You are in the latter group, and that's OK by me, as it allows me to keep thinking while you are doing, and there is balance in the universe...

 

[pardus]

I don't want to use a submachine gun I want a rifle, 10.5 inches just doesnt give me confidence.

Also I like bayonets and I want the prick on the other end as far away from me as possible if I were ever to get the chance to stick him.