What is the correct way to use a bench rest for an AR-15 and also bot-action rifles? I've heard conflicting stories...barrel on the front benchrest or forearm?

ideally, you need to isolate the barrel from support.  most bolt action barrels are free floated; not touching anything but the receiver.  AR; just rest the rifle on the benchrest with the forearms stock.  pressure on the barrel will effect it's accuracy.  there are AR's with free floated bbls.

now, this is a bit different when using a GI bipod on the AR, it clamps to the bbl just aft of the bayonet lug...but that was intended for full auto firing.

Ditto what 7 said.



definetely don't want the barrel touching anything to affect the harmonics.

Also most free float tubes are used so that when you sling up you don't bend the barrel and affect the POI while shooting.