I love pencil barrels so much that only one of my ARs does not sport one, and that is only because ArmaLite only offers 20" barrels for the AR-10 in the A2 profile. I do not find the weight to make that much of a difference in recoil, but it does make a big difference in comfort of carrying, and how easily and naturally they point and swing. I prefer the full-length 20" (or 21" in the case of the Dutch AR-10 I owned) in ARs, and find that their cycle is so smooth, rather like a modest 230gr load out of my Glock 37. Even my 16" barrels have rifle receiver extensions and fixed stocks, and all of them are midlengths, and even then, I vastly prefer that gentle and long push that the cycling action gives me on the 20", versus the short and sharp rap (not any heavier, just faster and more abrupt) of the 16" midlengths.
I have shot plenty of heavy barrel ARs (Colt LMG, AR-15A2 HBAR, etc.), but vastly preferred the large collection of classic and modern lightweight barrel models I have been lucky enough to shoot. These include:
- 1958 Cuban-contract ArmaLite AR-10, semi and full-auto
- Early Colt-ArmaLite AR-15s: 601, 603, and 604.
- Colt SP1 (with an M16-profile BCG, Geissele SSA-E FCG, a narrower rear aperture, and narrower front post it is one of the favorites of my collection)
- Every 5.56/.223 AR I own has a Criterion chrome-lined 1:8" twist pencil-contour barrel, either in 20" for the rifles and 16" for the midlenghts
The one time I actually did prefer a heavier barrel option was comparing the Cuban and Sudanese/Guatemalan contract AR-10s to the later Portuguese model. The former 2 have barrels that start out as narrow in profile as a SCAR-17, but that were then fluted to make them even lighter. Those rifles, even in semi with the gas turned way down (the Dutch-produced AR-10s had adjustable gas), were downright painful to shoot in a T-shirt, and even a leather jacket. The Portuguese, which is a pound and a half heavier, fitted with what could at most be called a medium-contour, unfluted barrel by today's standards, came in at 8.5lbs, and was far more comfortable to shoot. Some of this certainly owed, though, to the Portuguese rifle's rubber buttpad, while the Cuban and Sudanese sported a steel, Gewehr 98esque buttplate.