Argument for pencil barrels?

[Mysteryman]

Comparison between a M4 and M4a1 carbine firing to failure. M4a1 is fitted with a heavier barrel.*

Rounds fired: M4= 535, M4a1= 911

Footage taken in 2012. More info at NYTimes:*http://atwar.blogs.nytimes.com/2010/...and-m4a1-guns/

How many people have a select fire lower?
How many people have access to or carry 500-900 rounds?
How many people will ever need to fire 500-900 rounds in full auto in such a short period of time?

A heavier barrel means more mass. More mass means more energy can be stored before the barrel temp reaches the failure point. It's an interesting test but it isn't practical or realistic nor does it apply to 90% of AR owners regardless of their usage.

MM

[californiasushi]

I can't comment about the lightweight barrel you're looking at but we do have a 16" DD with a lightweight barrel (older model that was .625" at the gas block) with a Leupold Mk6 1-6x scope that functions as a "Recce" type build. I think it shoots well, about 1 MOA for a 5-shot group with Hornady 75gr BTHP handloads. We can use it to get a decent hit ratio on full sized torso steel at 907 yards with 75gr Hornady BTHP handloads. If your barrel can shoot well, it should do decently at longer distances if your wind calls are good. Since it's more of a "Recce" type build, I don't think you'll have as much of an issue with the traditional issues with regards to pencil barrels such as POI shift/groups opening up since you won't really be pouring rounds through it.

Here's a video we took of shooting a full-sized torso at 843 yards:



Here's a picture of our setup, it weighs 10.6# as pictured, complete with bipod, suppressor, and 20rd mag filled with 77's. Largely due to the lightweight barrel and lightweight suppressor (TB Ultra 7), it's lighter than our 12.5" build that is similarly configured except with a shorter barrel, Burris XTR II 1-5x scope, and heavier can (SiCo Specwar K):



However, perhaps due to the pencil barrel on our 16" DD, the POI shift with the can is quite a bit. It looked to be about a 6 MOA shift, but I didn't measure it exactly but I will next time I shoot unsuppressed.

[Iraqgunz]

This subject seems to come up all the time. Things that people should take into consideration.

1. What am I doing with this barrel?

2. Am I a member of SpaceshuttleSEALteam10DeltaGroupCAG conducting hostage rescue missions on Mars?

3. Am I going to do full auto magazine dumps with my new 500.00 drop in faux full auto trigger?

Based on my shooting experiences and what I have seen from others, a lightweight barrel is perfectly fine for a majority of shooters. I have shot mine out to 600 yards and was able to hit the targets and maintain relative accuracy.

[ColtSeavers]

How many people have a select fire lower?
How many people have access to or carry 500-900 rounds?
How many people will ever need to fire 500-900 rounds in full auto in such a short period of time?

A heavier barrel means more mass. More mass means more energy can be stored before the barrel temp reaches the failure point. It's an interesting test but it isn't practical or realistic nor does it apply to 90% of AR owners regardless of their usage.

MM

Don't know if this reply is specifically directed at me or not, but in case it is, I was simply showing one of the instances that a heavier profile barrel shines as this specific example was brought up by previous members' posts. I really should have used the quote feature to further illustrate that intent. My apologies for not doing so.

As I've posted in other similar threads, if you're going to ruck it all day go lighter. If you're going to go from the safe to the car to the bench, go with whatever profile you want. If you're going to mag dump or shoot for extreme accuracy and precision, go heavier. Generally speaking of course.

[556BlackRifle]

I just finished a build with a 16 inch pencil barrel from a well known company. Took it out to the range on Thursday afternoon. I shot AE black box 55 gr FMJ and my groups averaged about 4.5 inches at 50 yards. I used that same ammo on another rifle and shot a 10 shot group of 0.944 inches at 100 yards - so I know it's not ammo related. I'm going to check a few things and try again. I'll update as soon as I know more.

[tostado22]

If a gov't profile barrel has worked for you in the past a LW profile will be just fine. I've had LWs of different brands, mostly Sionics and BCM, on my last few general purpose carbine builds and have not been disappointed

[lysander]

Based on my shooting experiences and what I have seen from others, a lightweight barrel is perfectly fine for a majority of shooters. I have shot mine out to 600 yards and was able to hit the targets and maintain relative accuracy.

An awful lot of Marines qualified expert with an M16A1 between 1970 and 1990....so yeah, lightweight barrels are plenty accurate out to 500 meters/600 yards.

(Even with 55 grain bullets.)

[Benito]

Lightweight, heavy, pencil, tapered, they're all good. I'll take any of them over the Government profile, which is the most assbackwards profile possible.

[HansTheHobbit]

Comparison between a M4 and M4a1 carbine firing to failure. M4a1 is fitted with a heavier barrel.*

Rounds fired: M4= 535, M4a1= 911

Footage taken in 2012. More info at NYTimes:*http://atwar.blogs.nytimes.com/2010/...and-m4a1-guns/

I've seen that video before, and what they're not taking into account is that the rifling was cooked long before the barrels failed. That's the problem with meltdown videos is that they only prove how the rifle would perform under totally unrealistic conditions. Not only can no one carry that much ammo, but no one can fire that fast with any degree of accuracy. I would also have liked to see a temperature comparison at different stages. The heaver barrel didn't droop because of its rigidity, and that may have added a few hundred rounds. I can almost guarantee that the M4A1 got hotter because it cooked off rounds, whereas the M4 didn't. I think there's a really good chance that the throats of both barrels reached critical temp at about the same round count. However, I do think the video clearly demonstrates the folly of the M4 profile. Simply adding a few grams of material behind the gas journal would have kept it going longer, and removing the entire profile around the M4 cut would not have hurt anything. Not only would the barrel be lighter, but it would feel much lighter because of the redistribution of material.

Now normal sustained firing, in short bursts, may prove to be another story. That's what the R&D guy I spoke with didn't really know. He knew for a fact that full auto dumps would destroy the throat of any barrel, even a full bull profile, in the same amount of time, but he didn't know how many rounds a heavier barrel could buy you during normal rates of fire. I would love to see a manufacturer take two barrels, one light and one heavy, put both through the same course to simulate a realistic gunfight, and see how fast the throats get to critical temp.

[DreadPirateMoyer]

OP, the advice in this thread is excellent, especially that from IG. For 99.9% of civilian use, a thinner profile (BCM ELW, pencil, etc.) will be just fine and probably even preferable.

My only caution would be suppressor use. POI change tends to exaggerate with a skinny barrel when you hang a 1-2lb can off the end, and group dispersion due to heat also tends to happen faster in my experience since the can heats up the barrel faster than without, exacerbating the skinny barrel's lack of heat absorption. Because of this, I like Noveske's N4 profile barrels: still a lot better geometrically than a dumb government barrel, but thicker to help with the above.

That said, that's only for my high-rate-of-fire suppressed guns. I still use some thinner stainless barrels, even suppressed, as those are due for much less intensive firing schedules.