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Posted: 1/28/2006 7:06:42 PM EDT
[Last Edit: 1/28/2006 7:48:25 PM EDT by jurist]
From what I understand the M16 started out with a 20" barrel. Now the current issue M4s have 14.5" barrels. Law enforcement and NFA plinkers are now using barrels all of the way down to 9.25" and shorter barrels as higher caliber replacements for the MP5.

Workmanship, trigger, ammunition, barrel harmonics and whether the barrel is floated or not can all effect accuracy. Obviously barrel length is not the only thing that effects accuracy.

That said, does anyone have any idea how much accuracy you loose for every inch shorter the barrel is?

What is the difference in the accuracy and effective range of a 20" vs a 14.5" or a 14.5" vs a 12.5" barrel?

Link Posted: 1/28/2006 7:20:48 PM EDT
You're on the right track, almost. Barrel length has very little to do with its accuracy potential. It's all the other things you mentioned, and most importantly, the nut behind the wheel, that affect accuracy.
Link Posted: 1/28/2006 7:21:56 PM EDT
barrel length has nothing to do with accuracy, it has to do with velocity
Link Posted: 1/28/2006 7:39:45 PM EDT
I think barrel length does affect accuracy. Velocity is very important, but a good rotational spin must be initiated or no amount of velocity will help. How short is too short? It's all based upon the characteristics of the barrel and the bullet being utilized, so there is no set answer anyone can give.
Link Posted: 1/28/2006 7:57:35 PM EDT
[Last Edit: 1/29/2006 7:51:09 AM EDT by jurist]
I have always understood that velocity and accuracy over a distance were related, not necessarily a 1:1 ratio but still related none the less.

Theoretically, what sort of accuracy could you expect to get out of an M4 setup with a 12.5" Wilson Arms Match Grade Barrel, Noveske KX3 flash hider, Jard single stage match trigger, free floated barrel, harris bipod and I don't know black hills ammo at 200 or 300m? Lets also say the shooter is a good shot for arguement's sake.

I am just really wondering how much effect barrel length has on the whole picture.
Link Posted: 1/28/2006 8:19:31 PM EDT
With barrels as short as 6.5 inches, the big difference isn't until the wind starts pushing the bullet. Then longer barrels are easier to shoot.

Wes Grant at MSTN stated that he shot one of the tightest groups he has EVER shot with a gas gun, with a 12.5" barrel.
Link Posted: 1/28/2006 8:49:14 PM EDT
from my favorite gun shop:


"** Is a longer barrel more accurate than a short one?



No! Barrel length has nothing to do with the ability to shoot tight groups and may give LESS measurable

accuracy. A longer barrel MAY give a higher velocity = flatter shooting and more energy. A longer barrel,

particularly a thin, long barrel will have more vibration upon ignition and a poor quality long barrel has more

chance of internal defects in its greater length. Stick with a mid length medium - heavy weight quality barrel

for best accuracy.

P.S. We have seen many quality manufactured CHROME lined barrels shoot as well or BETTER than non

chromed. "


-Phoenix Armory Oregon City,OR USA

Link Posted: 1/28/2006 9:12:00 PM EDT
Thanks for the input y'all. My main concern is that I not end up dead on the side of the road shot by a trigger happy Meth cooker because I chose to put the standard issue out of the box Colt M4 with 16" barrel (that I am not allowed to shoot daily) in the trunk and carry my personal tricked out 12.5" barreled more manuverable M4 (that I practice with daily on my own time) in the front of the car.
Link Posted: 1/28/2006 9:28:08 PM EDT
Hmmm...out in the real world where the wind is usually blowing, longer barrel = higher velocity, therefore less drift when engaging targets at long range. With a constant wind not a big problem maybe, but with a gusty wind you are in trouble.

Also, higher velocity = less drop. Again this could be a problem at longer ranges or with the heavier bullets, where you are already short on velocity because of the greater bullet mass.

So, yes, short barrels can do the job; but why restrict yourself thus if you don't need to?
Link Posted: 1/29/2006 6:35:35 AM EDT
Link Posted: 1/29/2006 6:42:00 AM EDT
Link Posted: 1/29/2006 6:53:27 AM EDT
[Last Edit: 1/29/2006 6:54:14 AM EDT by Onslaught]

Originally Posted By jurist:
Thanks for the input y'all. My main concern is that I not end up dead on the side of the road shot by a trigger happy Meth cooker because I chose to put the standard issue out of the box Colt M4 with 16" barrel (that I am not allowed to shoot daily) in the trunk and carry my personal tricked out 12.5" barreled more manuverable M4 (that I practice with daily on my own time) in the front of the car.


What brand is your 12.5" barrel? That will have much more to do with the accuracy potential when compared to a rack grade barrel than length.

It has been shown many times on this site (and I have done it as well) that all you need to shoot accurately out to 500 or 600 yards is 14.5" of barrel. I don't have a shorter barrel to see if I could do the same with less.

At your "Meth cooker" distances (<300 yards?), I don't think you'll have absolutely anything to worry about regarding accuracy of your barrel.
Link Posted: 1/29/2006 6:57:11 AM EDT

Originally Posted By jurist:
Thanks for the input y'all. My main concern is that I not end up dead on the side of the road shot by a trigger happy Meth cooker because I chose to put the standard issue out of the box Colt M4 with 16" barrel (that I am not allowed to shoot daily) in the trunk and carry my personal tricked out 12.5" barreled more manuverable M4 (that I practice with daily on my own time) in the front of the car.


Are you a door kicker or sitting back? You need to look at what range you are going to be using it. If you're going inside then the bbl length isn't going to mean as much in terms of velocity/accuracy to you as it will in terms of moving around more easily. Otherwise, at the range you would normally be using it as an LEO on perimeter or even as overwatch you still would not have any noticeable difference. And if you are in overwatch, then a more dedicated weapon should be used anyway.
Barrel length isn't the biggest factor in accuracy unless you go to one of the extremes.
Link Posted: 1/29/2006 7:19:38 AM EDT
Link Posted: 1/29/2006 8:05:18 AM EDT
[Last Edit: 1/29/2006 8:10:38 AM EDT by jurist]
Wilson Arms Match Grade barrel. I'm not a paper pusher but I am not on the tactical team as per the wife and kid's orders. My problem is that I have found the 16" barrel on the M4 gets caught on everything in the car. We are in a rural area and I've been shot at on 6 different occassions in the past few years when I've driven to close to Meth cooking operations on some of the dirt roads I patrol. Normally the range isn't more than a couple of hundred yds. They still haven't hit me :) Although the occassion has not arisen that I have needed to do it, I have tried rolling out of my patrol car with the rifle in hand (and car in park) and it is no problem with the 12" but I keep getting hung up on the rear view and gear shit with the 16" (and just about everything else). (point well taken for anyone who is just dying to say that cops cannot shoot worth a d@mn. unlike most deputies I actually practice shooting daily on my farm. I grew up shooting AKs, UZIs, ARs, HKs, AUGs [Uncle was an SOT]).
Link Posted: 1/29/2006 8:31:15 AM EDT
I didn't mean sitting back as a member of the rubber gun squad. I jsut didn't knwo if you were making entry or setting the perimeter.
Anyway, I know exactly what you are talking about with the 16" in a vehicle. I went to the M4 14.5 so that I could move the weapon around in the vehicle, have it readily available, and minimize the snagging getting out.
As for taking fire from meth houses, I can see where that would be a problem, and in rural areas there will be some open terrain. In my area we have a lot of cattle pasture, cotton, corn, wheat, and hay fields. Also lots of rolling terrain.
You just need to think about whether it's safer and more effective to get out of the immediate danger area if the fire is ineffective and call in or if the situation merits returning fire. Liability grows exponentially over a few hundred yards.
Link Posted: 1/29/2006 8:47:53 AM EDT
[Last Edit: 1/29/2006 8:52:48 AM EDT by Onslaught]

Originally Posted By MSTN:

What brand is your 12.5" barrel?


PAC-NOR S/S POLYGONAL, BY JOHN NOVESKE.

YES, I AM AWARE THAT THE QUALITY OF THE BARREL IS KEY. MY POINT IS THAT THE SHORTER ONES SHOOT AS WELL AS THE LONGER ONES. IN MY PARTICULAR CASE, WITH THIS PARTICULAR BARREL, IT'S ABOUT AS TIGHT A GROUP AS I HAVE EVER SHOT WITH A 5.56MM GAS GUN.

WES GRANT
M.S.T.N.


Oh goodness no... That question (and proceeding comment) was not in any way directed to you Wes! Both were for Jurist. Geez, I'm not going to presume to tell YOU anything about barrel length or accuracy

And in case I've not been clear, I agree that shorter barrels are no less accurate than longer ones... I like my barrels SHORT!

Even still, I guess I missed this post by Jurist earlier which answered my "barrel brand" question:


Originally Posted By jurist:
I have always understood that velocity and accuracy over a distance were related, not necessarily a 1:1 ratio but still related none the less.

Theoretically, what sort of accuracy could you expect to get out of an M4 setup with a 12.5" Wilson Arms Match Grade Barrel, Noveske KX3 flash hider, Jard single stage match trigger, free floated barrel, harris bipod and I don't know black hills ammo at 200 or 300m? Lets also say the shooter is a good shot for arguement's sake.

I am just really wondering how much effect barrel length has on the whole picture.



Again, Wes can tell you better than me, but I think inside of 300m (hey, good guess on my part, huh?) should be well within the performance realm of your match grade 12.5". I've been very impressed with the Wilson match grade performance to price ratio.
Link Posted: 1/29/2006 12:00:51 PM EDT
[Last Edit: 1/31/2006 12:00:33 AM EDT by MSTN]
Link Posted: 1/29/2006 12:35:54 PM EDT
My thought on the matter is that shooters tend to be the limit of a weapons system, not ammunition or rifles.
Link Posted: 1/29/2006 1:47:14 PM EDT

Originally Posted By MSTN:
HERE'S A SNAPSHOT OF BARREL LENGTH PERFORMANCE WITH MK 262 MOD 1:


____________________________________________

MK 262 VELOCITY DATA
____________________________________________


7.5" 2053 FPS ... 10.5" 2363 FPS
DIFFERENCE 310 FPS
DIFFERENCE/INCH 103 FPS

10.5" 2363 FPS ... 14.5" 2576 FPS
DIFFERENCE 213 FPS
DIFFERENCE/INCH 53 FPS

14.5" 2576 FPS ... 16" 2669 FPS
DIFFERENCE 93 FPS
DIFFERENCE/INCH 62 FPS

16" 2669 FPS ... 18" 2769 FPS
DIFFERENCE 100 FPS
DIFFERENCE/INCH 50 FPS

18" 2769 FPS ... 20" 2818 FPS
DIFFERENCE 49 FPS
DIFFERENCE/INCH 25 FPS



THIS IS OF COURSE JUST ONE BARREL IN EACH LENGTH. THE 7.5" - 16" ARE ALL MIKE ROCK BUTTON RIFLES BARRELS. THE 18" IS A DOUGLAS S/S. THE 20" IS A KRIEGER S/S. ALL TWISTS 1X7" EXCEPT KRIEGER, WHICH IS 1X7.7". STANDARD DAY CONDITIONS.

WE SHOT XM193 ND M855, AS WELL. THEY FOLLOWED THE SAME CURVE.


WES GRANT
M.S.T.N.



For what it's worth I plugged these numbers into a spreadsheet and got the following numbers for longer barrels:

22" = 2877 fps

24" = 2914 fps

You can see the curve start to flatten out above 18"

Still, you are getting more velocity with more barrel length. With the 24" you are nearly at 63 gr. 20" velocities, a hell of a good thing with a 77 gr. bullet.

Currently all my ARs have 16" barrels, but I have an extra reciver and was considering doing a longer barrel to squeeze all I can out of the 77 gr load and my MR/T. I'm still dithering if a gain in velocity over the 16" of 5.6% (20"), 7.7% (22"), or 9.1% (24") is worth the extra length and weight. I'll have to dig out my old Statistics textbooks to see if there is a significant value to be had with these numbers.
Link Posted: 1/30/2006 11:17:10 PM EDT
Link Posted: 1/31/2006 10:13:22 AM EDT
Thanks y'all! everyone's comments have been really helpful. The graph really helped put it into perspective too. Thanks
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