HBARs really have only two reasons to exist:
- If you are using a standard-quality barrel, then the reason for an HBAR is if you have a full-auto rifle and plan to shoot high volumes of full-auto in a short amount of time. The HBAR will hold up better under that high heat.
- If you are using a match-quality barrel, AND have your barrel free-floated, AND are using match ammo, then having a heavy barrel will further help your accuracy by reducing movement caused by the shooter (a heavier rifle is harder to move), and the reduced barrel whip of the heavy barrel will make a tiny improvement in accuracy. Further, if you are taking multiple shots quickly (such as varminting), you'll retain that precision accuracy longer as the barrel heats up.
For any kind of field gun, MY opinion is that an HBAR is too heavy (again, unless you've got a belt-fed, or a long-range precision rifle, and then I hope you've got some guys to cover you with lightweight rifles!).
Most folks who attend a shooting school with an HBAR make ordering a lightweight barrel one of their first priorities upon getting back home. Just a quick example why: try holding your rifle on an object for 5 minutes, to simulate covering a dangerous bad guy until "support" (cops, or other folks to back you up) arrives. WITHOUT chambering a round, put a loaded mag in the rifle and hold it on something that's roughly man-sized and about 10' away. You'll find out how quickly your rifle gets heavy.
Beyond that, having to carry your rifle for any length of time, or to move it around, from target to target, as you do in a shooting school, is all much easier with a lighter-weight rifle. There's a reason why the military doesn't use HBARs except in their beltfeds.