I've never shot a gun with rearward pointing bipod legs - they're there for support, not to reduce recoil. You absorb recoil with your body, not with the ground.
The BAR I fired was all original parts, except the trigger/sear assembly which was modified to make it semi-auto only. That had no impact on the gas-piston action, which Rocket implies is responsible for the "pull". I suppose someone expecting the same kick that a Garand or Springfield '03 delivers might in fact jerk forward in anticipation of recoil when firing (I have a tendancy to do this when I pick up a .22 cal rifle after firing my 8mm Mauser all day), but it's certainly not any mechanical feature of the gun causing it.
Edit: Just found this! Tell me if that looks like "pull"
http://members.ozemail.com.au/~mickay/bar.htm
Cheers!
Panzerman