barrel ridgidity

[Falz24]

I can't decide between a BCM upper with a pencil barrel or govt profile (no cut out)

I like the fact that the pencil barrel is lightweight. But will it lose accuracy? I hear it does because it is not as ridgid

Any other reason not to get a pencil barrel other than it getting hot easier???

[Russ D]

It will lose accuracy under any type of rapid fire. The question you have to ask yourself is if the weight savings are worth it for your application.

[KBAR-04]

My Colt 6520 gave surprisingly good accuracy. I switched to a 6721 (16 inch heavy barrel) upper and it does better. Keep in mind if you want handiness, there is a significant weight difference between the two barrels, thats were most of your weight is in an AR... I went to the 6721 upper as I was trying to build a C8 type carbine similar to the ones I saw in use as a liaison with UK forces back in the day.

[RGoose]

What's your intended purpose? Is it a range toy that most likely won't see a great amount of heat cycling? Do you plan on taking carbine courses with it? Or is it a long distance/varmint gun (unlikely from your question).

I don't think you'll lose much accuracy with the pencil barrel, even in a high round count course; although you may sacrifice some barrel life for only (what I feel anyway) a small gain in rifle handling. There will be more barrel whip, but I'm honestly unsure if there will be a significant impact on accuracy within 100 yards or so.

Just like most things in life barrel choice is most often about compromise. Identify your intended use and go from there. Either way I don't think you can go wrong with a BCM barrel of either profile. My last upper is a 14.5 government profile mid length and it seems super light to me.

[Sgt_Gold]

Both barrels you mentioned will have the same profile under the handguards, so the only difference is from the front sight block forward. I have fired a lot of rounds through both M16A1's and M16A2's, and I don't think the heavier government profile on the A2 gave me any additional practical accuracy. A heavier barrel will absorb more heat, but unless you're going to do some heavy duty shooting i'd go with the lightest barrel.

[hunter123]

Both barrels you mentioned will have the same profile under the handguards, so the only difference is from the front sight block forward. I have fired a lot of rounds through both M16A1's and M16A2's, and I don't think the heavier government profile on the A2 gave me any additional practical accuracy. A heavier barrel will absorb more heat, but unless you're going to do some heavy duty shooting i'd go with the lightest barrel.

He nailed it on the head.

[benw315]

unless you're going to do some heavy duty shooting i'd go with the lightest barrel.

What would you define as "heavy duty shooting?"

[Magic_Salad0892]

I haven't shot my uncut KAC barrels for accuracy, but my 11'' gun has fired a 10 shot group just under an inch at 100 yards with BH Mk. 262, and a some handloads that I borrowed. Handloads were what I got under an inch out of, the BH got something like 1.2 or 1.3''.

I've said that on this board before.

Keep in mind, that when I had mine cut it was also re-crowned to an 11 degree chamfer, which from what I know is for SMK type boat tail rounds. Which may have helped with accuracy.

1:7 CHF LW barrel.

Those are tiny groups, and I seriously doubt a BCM barrel couldn't do the same or similar thing with a good crown, good trigger, and good ammo.

The KAC is considered lightweight.

[variablebinary]

I can't decide between a BCM upper with a pencil barrel or govt profile (no cut out)

I like the fact that the pencil barrel is lightweight. But will it lose accuracy? I hear it does because it is not as ridgid

Any other reason not to get a pencil barrel other than it getting hot easier???

A well made pencil barrel will survive any abuse you throw at it without significant loss of accuracy.

Your groups will open up slightly after a couple of mags, and your barrel will heat quicker, but its nothing to concern yourself with. I've watched Colt Commandos do multiple consecutive mag dumps without breaking a sweat and still make clean hits on a man sized target at 200 yards.

Once you go pencil barrel, its damn hard to go back to gov't profiles, and definitely not HBAR's. They shoot great, swing great, and are a real joy carry.

The 14.5" middy pencil barrel with light rail is God's gift to shooters.

[Sgt_Gold]

Sustained fully automatic fire or sustained semi auto firing with a suppressor is what I'd call heavy duty. Anything you do without a can on semi auto isn't going to hurt anything.


What would you define as "heavy duty shooting?"

[Molon]

The pic below shows the results of firing three 10-shot groups in a row from each of the displayed barrels in a semi-automatic AR-15, from a bench-rest at 100 yards using match-grade hand-loads.



Colt 16” light-weight (pencil) profile, 6520 – 1 pound, 6 ounces


http://www.box.net/shared/static/x7ykufvv3j.jpg




Colt 16” M4 (government profile), 6920 – 1 pound, 12 ounces.



http://www.box.net/shared/static/qhjpk4qlr3.jpg






Colt 16” HBAR, 6721 – 2 pounds, 3 ounces.


http://www.box.net/shared/static/3bnl8bdr23.jpg






http://www.box.net/shared/static/in8cal2pcg.jpg



….

[ra2bach]

The pic below shows the results of firing three 10-shot groups in a row from each of the displayed barrels in a semi-automatic AR-15, from a bench-rest at 100 yards using match-grade hand-loads.



Colt 16” light-weight (pencil) profile, 6520 – 1 pound, 6 ounces


Colt 16” M4 (government profile), 6920 – 1 pound, 12 ounces.


Colt 16” HBAR, 6721 – 2 pounds, 3 ounces.



….

I'm pretty sure I know the answer, but what's your analysis and conclusion of these three groups - are the lighter barrels opening up more as they get heated, or are they simply not as accurate initially as the H-bar?

[Quentin]

Thank you for that information, Molon!

[13MPG]

The pic below shows the results of firing three 10-shot groups in a row from each of the displayed barrels in a semi-automatic AR-15, from a bench-rest at 100 yards using match-grade hand-loads.

Thanks for the great post!

[Darkop]

The pic below shows the results of firing three 10-shot groups in a row from each of the displayed barrels in a semi-automatic AR-15, from a bench-rest at 100 yards using match-grade hand-loads.



Colt 16” light-weight (pencil) profile, 6520 – 1 pound, 6 ounces


http://www.box.net/shared/static/x7ykufvv3j.jpg




Colt 16” M4 (government profile), 6920 – 1 pound, 12 ounces.



http://www.box.net/shared/static/qhjpk4qlr3.jpg






Colt 16” HBAR, 6721 – 2 pounds, 3 ounces.


http://www.box.net/shared/static/3bnl8bdr23.jpg






http://www.box.net/shared/static/in8cal2pcg.jpg



….


Molon,
I conducted a similar test this summer, although the light weight profile rifle was not a colt. Also used a 6920 and 6721 using same lot Federal XM193 and an ACOG.

Although my groups were larger my end result was similar to yours. Out of my 9 AR's, my personal favorite is my Colt 6721 for XM193.

I always enjoy your posts.

Until that day,
Darkop