What makes an AR barrel lightweight?

[jchen012]

Hello. Newbie here. I am specifically referring to the CMMG barrels. What exactly makes them lightweight? Aren't the normal CMMG barrels and their lightweight barrels made from the same steel and don't they have the same characteristics like chromed lined, etc?

[LonghunterCO]

Light weight refers to the barrel having a smalled diameter (vs. a heavy barrel). Although there is no standard to what makes a barrel light weight it typically is a barrel with at least a government type profile running a .625" diameter FSB (front sight base). Some vendors sale barrel calling them light weight and run the typical .75" FSB. Not all are created equal.

[jchen012]

Are there any cons to having a smaller diameter (like accuracy)?

[28_days]

Are there any cons to having a smaller diameter (like accuracy)?

Under heavy use it will heat up quicker.

I've seen a lot of argument over the accuracy issue, though I don't see why it'd inherently be any less accurate than a standard government profile. You're going to have owners who claim it's more, less, or just as accurate no matter what profile it is. I'd assume you're buying a "fighting rifle" in which case I wouldn't be overly concerned with accuracy (as a stock AR will generally out-shoot it's owner), reliability is where your concern should lie.

[Robb Jensen]

Barrel weight is controlled by barrel length and barrel profile. Lightweight typically means the barrel is .625" diameter. Gov't profile typically means heavier (.750" gas seat) and about .730" from the gas block seat to the muzzle and .625-.650" under the handguards. Then there's the mid-weight (currently the craze). And then HBAR, HBARs (heavy barrels) are thicker under the handguards than the gas seat (.750" gas seat).

[carbinero]

LW will also cool faster. I don't see any accuracy benefit in gov't profile over LW, since you'd want more chamber support and heat sink there (e.g. Noveske's improved contour). ETA: Perhaps that's good rationale for the mid-con craze ;)

I have noticed slight stringing with LW which I didn't see as much with an HBAR, but for my purposes that is inconsequential.

[jchen012]

Thanks for the replies. I appreciate it, especially since you guys replied so early in the morning... Learned alot.