AR government profile versus lighter weight profiled barrels

[LittleLebowski]

I'm starting to prefer lighter profiled barrels than the ubiquitous government profile, thoughts on this?

[Colt191145lover]

The BCM ELW is fast becoming a favorite for a lot of guys ( and girls ) I know... I much prefer it the the standard govt profile and like it even more then the pencil barrel (.625 ) profile.

[SamuelBLong]

For most purposes I'm with you. No real change in accuracy or performance. Just makes for a lighter and faster handling gun.




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[WDW]

If I had to carry a rifle for a living & had a choice, it'd be a 6720 or similar gun for sure. I haven't really looked hard, but for the sake of discussion, does anyone offer a rifle length barrel with a LW profile?

[Malamute]

I liked the weight and accuracy of the older Colt SP-1's I've had in the past. I'd happily live with that weight again in a 20" gun. It was able to make 6-7 hits for 10 shots on prairie dogs @ 300 yards with a scope off the hood of the truck. They may have opened groups a bit when warm, but shot very well overall.

The older carbine I had was the fairly light barrel. It carried great also. I'm not so much a fan of heavier AR's especially short ones. Seems to defeat the purpose to some degree. If I have to deal with the weight, I'd as soon have more barrel to go along with it.

I guess most think in terms of the carbines rather than the 20" guns. I like the full size 20" guns overall and they are my default starting point when thinking about AR's. Is there a Govt profile in the carbines?

[LittleLebowski]

I'm loving my BCM 11.5" LW and now that I'm rebarreling my 5.45 AR, I'm considering a 14.5 pencil to replace the 16" gov't profile that I just burned out.

[BobM]

I'm thinking about rebareling both of my M&P15As with the lighter barrels to reduce the overall weight.

[MSparks909]

I'm really enjoying my 16" BCM ELW-F/13" KMR rifle that I recently finished building. It has become my go-to for a training/class/all-around AR. I have a 16" DD government profile barrel and while that doesn't feel too heavy, comparing it to the ELW-F/KMR setup is pretty wild. I'm ditching the heavy 12" quad rail on my DD for a 13" KMR. Barrel only has 3,500 rounds through it so no need to change it.

[Molon]

No real change in accuracy . . .




Whether or not you consider the difference in accuracy between the different barrel profiles to be significant is certainly debatable, but there most definitely is a difference in accuracy, between the light-weight profile, government profile and HBAR profile. The graphic below shows the results of firing three 10-shot groups in a row from a distance of 100 yards using match-grade handloads.



https://app.box.com/shared/static/h9jeod1yjx.jpg




https://app.box.com/shared/static/bxvg50q75r.jpg




https://app.box.com/shared/static/d28gzhg6fl.jpg




https://app.box.com/shared/static/8yz2obnogj.jpg




….

[SeriousStudent]

My favorite AR upper out of all the ones I own, is a BCM pencil barrel 16" middy with a 13" rail.

When it gets shot out next year, I'm going to replace it with this:

http://www.bravocompanyusa.com/BCM-BFH-16-LIGHT-WEIGHT-Mid-KMR-KEYMOD-p/bcm-urg-mid-16lw-bfh-kmr13.htm

I love that 13" KMR rail. I have handled that exact upper, and think it would be a dream if I had to tote an AR for a few days.

Hope that helps.

[LittleLebowski]

Molon, do you have any data on the effect of heat on a lightweight barrel's accuracy?

[ffhounddog]

I have to agree with you on a lighter barrel.

I like the material that the KMR is made from but can they make it without that keymod crap. Its just more stuff to get lost imho.

The new M4 profile makes things suck more when you add the peq-15, m68, scoutlight or m952, Knights Rail. I still would rather have the old M4 profile. You could at least get a decent balance in my opnion.

[TGS]

If I had to carry a rifle for a living & had a choice, it'd be a 6720 or similar gun for sure. I haven't really looked hard, but for the sake of discussion, does anyone offer a rifle length barrel with a LW profile?

Sure:

http://www.gmriflebarrel.com/m16-a1-5-56mm-20-1-12-twist-20-barrel/

If you want to lay down some more cash, Fulton Armory is pretty well respected for their retro rifles. They have an A1 clone called the FAR-15 (http://www.fulton-armory.com/fariflecal556mmupruniversalprecisionrifle-3-2-2-7-2.aspx) and you can purchase the pencil barrel (http://www.fulton-armory.com/barrelfa16m4gicontourcm1x9threadedchromelined-1.aspx) separately.

You could always have ADCO turn an existing barrel, as well.

[Vinh]

I haven't had much luck with lightweight barrels so far. My 16S is embarrassing out to 300 and my SR15 Mod0 fails to impress. It's been too long since I've shot an M4 profile to comment, but the heaviest AR barrel known to man in my MR556 almost makes XM193 look good.

[Jay Cunningham]

Kinda depends on what you need the gun to do.

[Guinnessman]

I'm loving my BCM 11.5" LW and now that I'm rebarreling my 5.45 AR, I'm considering a 14.5 pencil to replace the 16" gov't profile that I just burned out.

Out of curiosity, how many rounds did you put thru the 5.45 before the barrel went Tango Uniform?

[LittleLebowski]

Out of curiosity, how many rounds did you put thru the 5.45 before the barrel went Tango Uniform?

Both times, about 12-13k rounds. 1st time is detailed here (http://rationalgun.blogspot.com/2013/01/my-definitive-545x39mm-ar15-article.html).

[orionz06]

Molon, didn't you test the Noveske N4 at one point?

[rob_s]

Molon, didn't you test the Noveske N4 at one point?

Looks like it was halfway between the HBAR and M4, which makes sense, at 0.37

http://beta.ar15.com/archive/topic.html?b=3&f=12&t=398208

I thought I had seen some pretty good reports of the ELW-F accuracy but can't seem to dig them up now.

[Chuck Haggard]

For carbines I have always preferred the "pencil" a1 profile barrels. It's a carbine.

Even with M16s, and I have had to carry a few of them for a few miles, I prefer the a1 over the a2 profile any day of the week.

[LittleLebowski]

For carbines I have always preferred the "pencil" a1 profile barrels. It's a carbine.


That is how I feel.

[Unobtanium]

Whether or not you consider the difference in accuracy between the different barrel profiles to be significant is certainly debatable, but there most definitely is a difference in accuracy, between the light-weight profile, government profile and HBAR profile. The graphic below shows the results of firing three 10-shot groups in a row from a distance of 100 yards using match-grade handloads.



https://app.box.com/shared/static/h9jeod1yjx.jpg




https://app.box.com/shared/static/bxvg50q75r.jpg




https://app.box.com/shared/static/d28gzhg6fl.jpg




https://app.box.com/shared/static/8yz2obnogj.jpg




….

Exactly. The argument about thermal mass, etc. is not necessarily at the heart of my reasoning, either.

Both barrels are the same contour/diameter where they get the hottest.

Both barrels have the same "minimum diameter".

It is my opinion that the contour of the .GOV profile "deadens" harmonics, some. I can't prove it, but I feel that this is the case more than the thermal mass equation.

[Byron]

Whether or not you consider the difference in accuracy between the different barrel profiles to be significant is certainly debatable, but there most definitely is a difference in accuracy, between the light-weight profile, government profile and HBAR profile. The graphic below shows the results of firing three 10-shot groups in a row from a distance of 100 yards using match-grade handloads.
As always, I really appreciate your data. Not only do I find your posts educational, but I have a vast amount of respect for the level of care and repeatability you build into your testing protocols.

Regarding the topic at hand, I'm just thrilled that so many lightweight options are now available off-the-shelf from reputable manufacturers.

In 2009 I built my first pencil middy. I had been on a waiting list for months to get a lightweight 16" middy from CMMG, but thankfully that fell through. For lack of better options, I had to start with a 16" BCM "govt profile" middy and have Robb Jensen at VA Arms Co reprofile and chop it (I ended up going 14.5" + perm FH).

Then 2010 gave us a tsunami of lightweight barrels and uppers; lengths from 10.5" to 16"; gas from pistol to middy; manufacturers including Colt, BCM, DD, etc.

Only speaking personally, the pencils give me everything that I "need" in the most convenient/comfortable envelope. I do most of my carbine shooting under 50 yards, and all of it under 100. A lightweight mean radius of 0.58" compared to the govt profile mean radius of 0.42" is an inconsequential difference to me at 100 yards.

I still have other AR's with heavier barrels, but they're just kind of "meh" for me now. I don't feel any need to reprofile them, sell them off for replacements, or anything like that... but I doubt I'll ever buy another barrel/upper that isn't a pencil. Again, I'm not questioning the usefulness or niche of heavier barrels: I just don't care about that niche.

[Molon]

Molon, do you have any data on the effect of heat on a lightweight barrel's accuracy?

Nothing verifiable at this point in time.

[Molon]

Molon, didn't you test the Noveske N4 at one point?

Noveske 16" N4 Barrel

http://www.box.net/shared/static/od2lkjgq1f.jpg



I performed an accuracy evaluation of my Noveske 16” N4 Light Recce upper following my usual protocol. Testing was performed from a distance of 100 yards. Firing was conducted from a concrete bench with the free-float handguard resting in a Sinclair Bench Rest. The rear stock of the rifle rested in a Protektor bunny-ear bag. Wind conditions were monitored using a Wind Probe. A Leupold VARI-X III set at 25X magnification and adjusted to be parallax free at 100 yards was used for sighting.

Using hand-loaded, match grade ammunition I fired three, 10-shot groups in a row. The extreme spreads of those groups measured:

1.29”
1.18”
1.31”

for a 10-shot average extreme spread of 1.26”. I over-layed those three groups on each other using RSI Shooting Lab to form a 30-shot composite group. The mean radius for the composite group was 0.37”.

After firing the above three groups, I fired an additional five, 10-shot groups in a row using the same set-up for a total of eight, 10-shot groups. The average extreme spread for all eight groups was 1.24”. I over-layed all eight groups on each using RSI Shooting Lab to form an 80-shot composite group. The mean radius for that composite group was 0.39”.


Noveske 14.5" N4 Barrel
https://app.box.com/shared/static/l7urmfkhn9hcynpuncsk.jpg



The 14.5” N4 barrel was tested in the same manner as described above. Three 10-shot groups fired from 100 yards using match grade hand-loads had extreme spreads of:

1.029”
1.360”
1.275”

for a 10-shot group average of 1.22”. As above, I over-layed the three 10-shot groups on each other using RSI Shooting lab to form a 30-shot composite group. The mean radius for that composite group was 0.37”.



....

[dookie1481]

Anecdote:

Took a class with Frank Proctor yesterday, and this question came up. He said that he saw no practical difference between govt and LW at 200 yds under sustained fire until about the 80 rd mark. After that point, it opened up BADLY, as in shots dropping 2 feet or so off target. Not data, but an observation from an experienced guy.

[Lester Polfus]

Anecdote:

Took a class with Frank Proctor yesterday, and this question came up. He said that he saw no practical difference between govt and LW at 200 yds under sustained fire until about the 80 rd mark. After that point, it opened up BADLY, as in shots dropping 2 feet or so off target. Not data, but an observation from an experienced guy.

I'll add my less useful anecdotal data to his anecdotal data. I owned a 16" pencil barrel for several years and my experience mirrored that. It actually did better than I expected for 60-80 rounds, not doing mag dumps but definitely "sustained fire" with little change, and then it seemed to reach a tipping point and poop out accuracy wise and it fell of quickly.

I was pretty ok with that.

[dookie1481]

I'll add my less useful anecdotal data to his anecdotal data. I owned a 16" pencil barrel for several years and my experience mirrored that. It actually did better than I expected for 60-80 rounds, not doing mag dumps but definitely "sustained fire" with little change, and then it seemed to reach a tipping point and poop out accuracy wise and it fell of quickly.

I was pretty ok with that.

Same here, its a blaster, not a precision piece. Right tool for the job and all that.

[Unobtanium]

Anecdote:

Took a class with Frank Proctor yesterday, and this question came up. He said that he saw no practical difference between govt and LW at 200 yds under sustained fire until about the 80 rd mark. After that point, it opened up BADLY, as in shots dropping 2 feet or so off target. Not data, but an observation from an experienced guy.
implying the .gov did not fall off a cliff? At what point did it?