Please direct me if this has been covered somewhere else....Is there any difference between an M4 barrel and a dissipator barrel besides the sight radius? Pros? Cons?

There is Two Dissipator barrels one is HBAR or heavy barrel and then there is a M4 profile barrel I would prefer the M4 because of the lighter weight

I agree with the lighter barrel idea, but I'm still not sure what makes a dissipator barrel different than any of the others.

In the case of the BM dissipator barrels, the only difference between them and a "normal" 16-inch barrel is the additional FSB, with the functional gas block being a "shaved" FSB.

There we go, thanks!  I wasn't sure if there was anything special about them but now I do.  Thanks again.

A dissapator barrel is a normal 16 inch barrel with an additional gas block placed near the end of the barrel at the same location as a 20 inch rifle.  The gas block nearest the receiver is the only one that functions in the gas system.  It is milled off so the handguards can go over it. The secone gas block at the front of the barrel is used only to hold the handguards and function as the front sight post.  You get the sight radius of a rifle with the gas system of a carbine.

The M4 version is just a little lighter than the Hbar version