M4 profile vs. Pencil Barrels

[Sooper Jenius]

It's been suggested in several articles I've read recently that, when building a defensive carbine (which I am), a pencil barrel might actually be more desirable than an M4 profile because they are lighter and, therefore, easier to handle. After I finished my last build I've decided against even a quad rail on this one - anywhere I can save weight I will. But I'm wondering at what cost. I do intend to plink with it at the range as well, so I do want the barrell to last.
How long will the barrel last compared to an M4 profile (I should mention cold hammer forged chrome lined pencil barrel vs. cold hammer forged chrome lined M4 profile)? Any difference?
How much more will it heat up?
Keeping in mind it's a semi-auto and not a machine gun, does the extra heat matter much to the life expectency?
I know it won't be as acurate as, say, a bull barrel, but for this purpose, any AR will probably be more than acurate enough.
Opinions?

[X-Man]

SJ; I'd like to add to and expand the question to include; is there any advantage to a mid length barrel at 16" compared to a 16" M-4?

If I understand, one of the differences is the front sight base on the mid length is closer to the muzzle, providing a longer sight radius.

I'm thinking on how to assemble a lightweight carbine with a 16" barrel.

[nfafan]

I recall reading on more than one board that the big issue was gas port location relative to the muzzle. The gist of the thread was to go with mid-length or rifle-length, or if you must go short; 10.5" bbl with permanent 5.5 flashider.

Wish I saved the links to the discussion; IIRC they had tech notes on a barrel company's website that supported the discussion. Others may know what I'm referring to.

Meanwhile, I saved this from the Armalite site; they apparently have a carbine where the gas port is shifted 2" to allow for the 16" bbl look while providing the "correct" gas:muzzle ratio.

http://www.armalite.com/images/Tech%...824….pdf

IMHO; unless you have the NFA fun-switch and lottsa drachmas for ammo, you may have nothing to worry over regardless of choice. So - pick what you like.
Me; I think rifles, mids, and pencil bbls are a nice change of pace from the seen-everywhere M4rgerys.

Edit:
The IDF builds are always nice examples of the KISS rifles.
http://www.ar15.com/forums/topic.htm...f=123&t=489699

http://98.196.65.94/retroblackrifle/...liMenusar.html

[ungawa]

If you are going for looks, M4. If you are going for purpose, pencil. M16 is better when light.

[Legion_Prime]

Interesting paper there. I am curious as to why if one "must go short" would a 10.5" with a 5.5" FH be considered. It would be the worst of both worlds, an SBR with a long barrel and a non-SBR with SBR performance. If you do not want to go the NFA route but still want the shortest package possible then go with a 14.5" with permanantly mounted flash hider. It gives you the minimum barrel length with the maximum barrel length behind the FH/comp. Bravo Co I know is currently offering their 14.5" middy with permanantly mounted Phantom or FSC556.
As far as govt vs pencil profile I'd say go with the pencil barrel. The govt profile is about the same under the HG's and is just thicker out front with an M203 cut. The typical barrel profiles can be seen here.
http://www.ar15barrels.com/profiles.shtml
If you have a choice I'd say go pencil barrel and I'd want a midlength gas system. They are lighter and with most of the difference in mass being the part of the barrel the furthest from you there will be a noticeable difference when manipulating the rifle however there will also be an increase in perceived recoil as there is less mass to act on. Middy's are easier on the rifle as the reciprocating mass is not not moving as abruptly or as fast due to the lower port pressures which results in a smoother recoil impulse and lower perceived recoil and longer part life over a carbine length gas system. The pencil barrel will heat up a bit quicker but the difference should not be that much firing in semi on the 1way range as the main difference in mass is out past the gas block and the main source of concern tends to be be the heat's affect on throat erosion back by the barrel extension.

[ScotsGuards]

In keeping within the paramiters of the original question; the short answer is: Unless you are constantly using the rifle in as rapid a fire mode as you can do in semi only, either barrel life should be about the same. The lighter barrel will handle a bit better as a light carbine, the M-4 will give you just a bit more accuracy as it heats up. However for all practical purposes, there should be little difference in overall handling. I have both and love them equaly. Though with my recent shoulder problems the lighter barrel carbine has been my first choice due to less strain on my left arm.

[Asmodeus6]

I have the lightweight barrel in my DPMS and the answer is;

4 mags rapid fire.

And even well heat shielded hand guards are starting to get very warm. The indexing washer on my FSC556 however is near glowing hot. The slightest touch of anything other than the hand guard say like an slight accident setting the rifle down and it will sear clean through your skin.

Ask me how I found that out...

Obviously I was just drilling COM targets between 40 and 20yds and practicing mag changes and getting the gun back up and runnning as fast as possible so I can't report on accuracy changes. But that being said I still did not notice any POI changes / problems when it was flaming hot.

I probably could have ran another mag or two through the weapon before it would have started to become uncomfortable for me to shoot. But the barrel was scorching hot and I don't have money to just be buying barrels because I feel like burning them up.

It does seem to cool fairly quickly though. Mine is non-chrome lined as well.

[Legion_Prime]

What chamber does it have? 5.56 NATO or DPMS 5.56 aka .223

[nfafan]

Interesting paper there. I am curious as to why if one "must go short" would a 10.5" with a 5.5" FH be considered. It would be the worst of both worlds, an SBR with a long barrel and a non-SBR with SBR performance. If you do not want to go the NFA route but still want the shortest package possible then go with a 14.5" with permanantly mounted flash hider.

<snip>

Middy's are easier on the rifle as the reciprocating mass is not not moving as abruptly or as fast due to the lower port pressures which results in a smoother recoil impulse and lower perceived recoil and longer part life over a carbine length gas system.

<snip>

Wish I'd have saved the links to the discussion as it was rather interesting in a dry kinda way. Sold me on the middy for a possible future acquisition, that's for sure.

But IIRC, it all centered around the distance between muzzle and gas port and how this affected the gas pressures of driving the bolt back. And how it was all "perfected" in the as-designed 20" rifle.
There was then a basic comparo between the rifle, middy, and some "shorty" in terms of maintaining the optimal gas port-muzzle distance as found in the original rifle.

[Asmodeus6]

What chamber does it have? DPMS 5.56 aka .223

That one.



Says 5.56 but I probably won't test my luck. I shoot steel case predominantly though it. Federal bulk packs, AE 64gr tracers... I haven't bought any Lake City or surp as I don't reload. So it's a waste to shoot brass for me.