I was looking at buying a 16" pencil barreled upper for my M4 lower. Currently it has a nice M4 upper with Aimpoint, BUIS, m33 foreend, a tango down VFG, and a phantom. I would like to get a pencil upper w/ an Eotech for some lightweight action. I handled a pencil barreled colt in the gunshop the other day and really liked the weight reduction and change of balance. I think that getting this setup, a few more mags, some magpuls, a load bearing tac-vest, and an Isreali style sling would make for a sweet go-to gun package. So wadda you guys think? Pros & Cons of the pencil barrel?

I cn't think of any disadvantage to a lightweight barrel.   Both my 10.25" and 14.5" duty rifles have, or will have, that barrel style on them.  Unless you're using a M203 you might as well save the weight.  

I have one.  No complaints.  It's gonna get hot faster than an M4 profile barrel and probably won't be as accurate, other things equal.

For $600 you can get one of ABS's carbon wrapped barrels and have the best of both worlds

Quoted: I have one.  No complaints.  It's gonna get hot faster than an M4 profile barrel and probably won't be as accurate, other things equal. For $600 you can get one of ABS's carbon wrapped barrels and have the best of both worlds hr

Any reason for the loss of accuracy?

Quoted: Quoted: I have one.  No complaints.  It's gonna get hot faster than an M4 profile barrel and probably won't be as accurate, other things equal. For $600 you can get one of ABS's carbon wrapped barrels and have the best of both worlds Any reason for the loss of accuracy?

No real loss of accuracy, but it will heat up faster, thus shifting POI sooner.  But it will also cool faster than an M4 profile....

It's my favorite barrel. I have four of them.

Quoted: Any reason for the loss of accuracy?

Heavier barrels are stiffer than lighter ones.  That's why you see heavier profiles on target and varmint guns.  That said, all my ARs have "pencil" barrels and shoot well.  My A1 style rifle has a USGI 1x12 pencil barrel and shoots better than it's supposed to with XM193 and Q3131A.  IIRC the dispersion spec for the ammo is 2 MOA and my rifle will shoot 1 to 1.5" groups at 100 yards.  My Superlight doesn't shoot quite as well, but will still print 2" groups at 100 yards (all w/the iron sights).

I have one and would recomend them.  They just feel right.