Barrels: pencil vs M4

[Wondering Beard]

I understand that the cutout on the M4 barrel is to enable the attachment of the M203 but putting that aside is there any advantage of the M4 barrel profile over the pencil barrel?

If I'm understanding things correctly the only difference between the two is past the FSB where the M4 is thicker and has the cutout. As a result, it is not only heavier up front (which affects balance) but doesn't have any advantage over the pencil barrel in the areas where things get really hot, i.e. between the chamber and the gas port. So the M4 isn't really more dureable than the skinny type.

Am I correct about that?

Also, as I understand it, barrel rigidity is is very helpful to obtain more accuracy but it doesn't seem to me that the extra thickness after the FSB of the M4 barrell would necessarily make for a more rigid barrel overall.

Wouldn't it thus be the case that the pencil barrel but better for the typical purpose of the M4 type carbine (LEO work, personal defense ..) that doesn't have a need for the M203?

[Paulo_Santos]

They are pretty similar except after the gas block, where the pencil barrel is skinnier. Unless you are shooting from a bench, you won't notice much of a difference in accuracy. The only thing to keep in mind with the pencil barrels is that if you use a sling as a shooting aid, you may want to use a Free FLoat Handguard because you will get a POI shift if you pull on the sling real hard.

[rob_s]

Most people are "coming around" to your way of thinking. For years the market was bass-ackwards and the tail was wagging the dog. Manufacturers and retailers only offered the M4 profile on commercial ARs thinking that was what the consumer wanted (to have a gun that looks like the issue gun) and then pointed to the fact that M4-profile sales outpaced lightweight barrel sales. It was, and still is, a ridiculous arrangement.

Finally consumers have been getting training and otherwise really pushing their guns and have begun to appreciate reduced weight and especially reduced weight at the end of a lever, and especially when, as you point out, the added weight offers zero benefit when there is a thin profile where it matters. The result is that more and more manufacturers are finally offering high-quality lightweight barrels and we no longer have to sacrifice material quality, proper testing, and chrome-lining just to save a little weight.

Having been preaching lightweight barrels uber alles for over 5 years now, often to idiotic ridicule like "if your gun is too heavy you need to do more pushups", I am very happy to see the wide array off choices we have now, and the future choices that are about to hit the market in the next 6 months or so, and especially more and more shooters coming 'round the to benefits.

[Optimus Prime]

FWIW, the military went with the exposed portions on the M16A2 (Gov't profile barrel) to give it more strength and prevent bent barrels during bayonet fighting. So if you're not doing a lot of bayonet training or running full auto, you can probably get away with a thin profile barrel.

[Creeky73]

I just ordered a 16" pencil profile upper from Bravo Company last week, and I can't wait for it to get here. I figured since my other AR is going to be a 20" govt profile, I might as well make this build as light as possible without getting into sbr's. I think I will be pretty happy with it.

[rebelEMPIRE]

"BCM Standard 16" (LIGHT WEIGHT) Mid Length Barrel, Stripped (.625)" -- This has been on my list for a long time. Waiting and waiting, and now that it's out, I have no funds for another build (because I built another rifle for a different purpose. Time to save up again!

-rebelEMPIRE

[Dos Cylindros]

I have a BCM 16" light weight middy and I love it. My dept. issue carbine is a true Colt M-4 and I like my 16" LW middy much better.

[Wondering Beard]

The last comments on lightweight middys makes me want to apply my original question to barrels for midlength systems.

Any advantage at all to the thickening of the barrel after the gas port on midlengths?

it would seem to me it just moves the balance point even further forward than in the carbine and still not add much of anything to the accuracy or dureability of the barrel compared to the skinny type.

Am I wrong?

[rebelEMPIRE]

Other than throwing the weight out forward and helping ever so slightly in stabilizing the aim and reducing recoil (because heavier things resist movement more), I see no other benefits. Really, as we all know, a chain is as strong as its weakest link. The only foreseeable difference between thickening of the barrel beyond the gas port of carbine barrels vs midlength barrels is the midlength will weigh less, granted both barrels are of the same length, similar profile, and metal composition. There are many other reasons why people prefer midlengths over carbine length barrels (with disregard to barrel profile), but that's for another thread.

-rebelEMPIRE

[markm]

So the M4 isn't really more dureable than the skinny type.

The more material in the barrel, the more durable. Even if the material is up front it can still absorb heat. Steel conducts heat.
The Army's test showed a dramatic durability increase between the standard M4 barrel and the Heavy profile barrel.

[Jimbo45]

The more material in the barrel, the more durable. Even if the material is up front it can still absorb heat. Steel conducts heat.
The Army's test showed a dramatic durability increase between the standard M4 barrel and the Heavy profile barrel.

Yes, but I think the discussion is about a comparison of pencil profiles to M4 profiles, not M4 profiles to heavy profiles. I have a feeling if the Army conducted a test, comparing durability between a pencil barrel and an M4 barrel, the durability difference wouldn't be quite so dramatic, in any at all.

[markm]

I guess we can only speculate. Obviously the Mil would never deploy a "pencil" barrel so we'll never know.

[Jimbo45]

I guess we can only speculate. Obviously the Mil would never deploy a "pencil" barrel so we'll never know.

Very true.

[rob_s]

I guess we can only speculate. Obviously the Mil would never deploy a "pencil" barrel so we'll never know.

I don't know if I'd go that far. They did with the original M16, and IIRC there are versions of the SCAR with relatively light barrels.

[todd.k]

The rear half of the M4/M16A2 barrels are pencil contour.