5.56 fired through short barrels

[Box]

I need some good information on shooting 5.56 through short barreled guns...

-What effect does the short barreled SAW have on the efficiency of the 5.56 ammo?
-Is there any ballistic (or any other "real" benefit) benefit over using 5.56 ammo in guns with a ten inch barrel ?
-Is there documented results as opposed to "I like the short barrels because... "

I suspect that there is little or no real benefit over the carbine barrel except for the fact that it allows some guys to look cool and feel good about their image, but I am not a ballistics expert, I am just a bit curious of this new found fascination with short barrels by new guys. I can only find info that supports a decrease in effectiveness with short barrels using military grade ammo.

Keep in mind I am only interested in milspec weaponry using standard issue 'green tip' ammo, not custom grade barrels made with different rifling twist and specialty or non-standard ammo.

Somebody smart please square me away so I can be smart also.

[The Reaper]

PM sent, Billy.

TR

[Box]

Many thanks sir.
That helps a ton.

[18C4V]

Originally Posted by The Reaper

PM sent, Billy.

TR

Sir,
Can you send me that info too?

[The Reaper]

This has been discussed here and elsewhere. Let me hit the highlights and provide an executive summary.

Like many things in life, it is a compromise. Shorter barrels equal lower muzzle velocity, period. Lower muzzle velocity, for the 5.56, is a bad thing. It seriously affects lethality, and makes shot placement harder due to increased bullet drop.

M855 ammo exacerbates this problem. It is slower, less effective, shorter range, and less accurate than the M193 it replaced. The Mk 262 is a better choice for most purposes, if you can get it, and it is much more accurate than the M855 or the M193, for that matter.

Since the M-16 was designed to function with a 20" barrel, anything less represents a potential reliability problem. 20" M-16s run, almost always reliably. 18" SPRs usually present no problems. 16" M-4s are almost as good. 14.5" M-4s are starting to get to the barrel length where problems pop up. A 10.5" or 11.5" CQB-R is really a race car. When it runs, it runs at the bleeding edge of reliability. Some do not run out of the box. The ones that do will require significantly more care and maintenance to keep running.

A 10.5" should really be treated as a submachine gun. If you are in a vehicle or doing dedicated CQB with little need to engage targets beyond 25 meters, it is a great weapons package. You can hit targets well beyond that range, but shot placement is going to be critical. It is also more easily concealed than the M-4 or M-16. IMHO, too many people carry them because of the CDI factor and they look cool.

The 14.5" M-4 is a carbine. It is able to reach out and put targets down reliably out to 100 meters or so. It has some of the advantages of the CQB-R, and some of the same disadvantages. If you need a weapon to do everything, with a healthy dose of vehicle, aircraft, or CQB work, yet still need to reach out a little further on occasion, the M-4 is your baby. Honestly, it should not be the dedicated weapon for a conventional infantryman in a non-CQB environment.

If you need the gun to be completely reliable, to reach out beyond 100 meters and drop people regularly to 200 or so, provide better precision, yet do not do a lot of mounted or airmobile infiltration, and have little need for a CQB weapon, then the M-16 rifle is your baby. If you are in OEF and are getting into far ambushes and engagements beyond grenade range, you need the rifle, not a carbine or SMG.

The full-length M-249 SAW is a squad automatic weapon. The shorter version is a specialty weapon, and if you have to ask, you aren't special enough to need one.

In my opinion, the shorter barrels are more status symbols than anything else. "Look at me, I'm special!" If you are doing dedicated CQB, PSDs, or almost exclusively mounted ops (and shooting the weapon from inside the vehicle), the 10.5" CQB-R might make sense. If you are not, the M-4 is a better choice, more effective, and more reliable as well.

Just my .02, YMMV.

TR

[koz]

I chrono'd some M193 from a 10.5" barrel - it averaged 2350fps. I used the www.handloads.com/calc/ for the numbers

Here's the chart -
55gr , BC - .221 (based on velocity), 2350 fps, standard atmosphere,

Range FPS Energy ft/lbs
0 2350 647
50 2157 568
100 1978 478
150 1810 400
200 1652 333
250 1506 277
300 1375 231

[charlietwo]

Many thanks, Reaper. Nothing beats hip pocket training

[MeC86]

Thanks for the info. I use a 10.5 inch and was curious about how the QP's felt about them.

[koz]

I was interested in the necessary fps for the M193 to fragment. So I did some searching and it seems like the consensus: 2500-2700 fps are needed for the bullet to fragment. Like TR said, it's like a sub-gun. Not much lethality (except with good shot placement) past 25m.

[The Reaper]

I have gotten closer to 2500 fps from the 10.5" barrels with M193, but it is still not something you can count on to fragment.

Those who can use ammo other than Ball have some additional options.

TR

[st1650]

I'm starting handloading .223 and I was wondering if any of you had SD load suggestions for a 11.5" 1/9 twist Armalite barrel. I think I would be better served with a 1/7 but it'll have to wait.

So far I've been using RUAG 63gr 5.56. http://en.wikipedia.org/wiki/Gw_Pat.90
Sub-moa with my 4x TA31 at 100yrds. Haven't chrono'd it yet. Should I stay with it or try some heavier grain, I've been looking at Hornady 68gr BTHP, SMK BHPT 69 gr.


As for reliability, I know it can't compare with the field, but I've never had any malfunction on mine. (Shot close to 10k of rounds).

[JJ_BPK]

Originally Posted by Brush Okie

I am looking for recommendations on ammo for self defense out of an 16" bbl AR with a 1-12 twist. I was looking at the Hornady Vmax 55 gr but not sure if it would expand to fast especially after looking at the shooting link posted in another thread where the 55 gr TAP was ineffective. The rifle would be carried in the mountains and range would be 100 yards or less. Hard to articulate a threat that is 500 M away.

I would try the heaviest slug you can accurately throw at 200 yds..

1:12 is slow and normally lends itself to light slugs,, but you may be able to get the 62gr to acceptable levels. I'd try some M855A1.. or heavery slugs like Federal Gold Medal Match 77gr. BTHP..

Once the M855A1 replaces the leaded M855, it will reduce the amount of lead in production by approximately 2,000 metric tons yearly, based on the amount now used to make the M855.

C Attached..

Acceptable accuracy is the key. If the critter has a 15 MOA bull on their chest,, 5 MOA may be OK..

[Air.177]

Originally Posted by Brush Okie

I am looking for recommendations on ammo for self defense out of an 16" bbl AR with a 1-12 twist. I was looking at the Hornady Vmax 55 gr but not sure if it would expand to fast especially after looking at the shooting link posted in another thread where the 55 gr TAP was ineffective. The rifle would be carried in the mountains and range would be 100 yards or less. Hard to articulate a threat that is 500 M away.

I would test the waters and see just how heavy a bullet you can get away with and still retain the accuracy standards you are looking for. I think the 70/75/77gr stuff is pretty much out of the question unless you go to a different upper, but check out the Federal 62 gr "tactical bonded" stuff and also Black hills loads a 50 gr Barnes TSX that while quite light for my preference, would also be worth looking into.

HTH

Good times,
Blake

[Team Sergeant]

Originally Posted by Brush Okie

I am looking for recommendations on ammo for self defense out of an 16" bbl AR with a 1-12 twist. I was looking at the Hornady Vmax 55 gr but not sure if it would expand to fast especially after looking at the shooting link posted in another thread where the 55 gr TAP was ineffective. The rifle would be carried in the mountains and range would be 100 yards or less. Hard to articulate a threat that is 500 M away.

I'd answer your question but every time I try your avatar breaks my concentration.

[35NCO]

In "Surefire-Combat Tactics" Fall 2011 volume 9, number 2 There is a very substantial scientific study on short barrels. The study was conducted by Dr. Philip H. Dater of GEMTECH. I hate these types of magazines, but whenever Dr. Dater publishes something, I read it.

The study starts with a 24" barrel and they keep measuring pressures until they reach 5 inches. The barrel was hacked off at 1" increments. The study also covers the relationship of velocity and barrel length. Incredibly interesting stuff if your putting a can on a short barrel. You may be able to find the study without buying the magazine. I don't think I can legally type it all in here, but I will post two examples for the sake of interest.

A 24" Barrel has a port pressure of 4,800 PSI with a Velocity of 2,964FPS and a sound level of 162.5dB(A)

A 10" Barrel has a port pressure of 12,140 PSI with a Velocity of 2,575FPS and a sound level of 164.3 dB(A)

The study was conducted to MIL-STD 1474D the ammo was M855 from the same lot.

Study also proves that barrels less than 10 inches on VSBR's are absolutely not worth it. Also, VSBR's will most certainly blow up your can after a very short period.