[Rancid Coolaid]

What optic is on the rifle?

I have a friend with a 16" 300WTF and he has seen not stellar results with his 220-gr factory subsonics (which have, for reference, all been subsonic - in Houston.) I have shot 2 boxes of the factory sub and it is nowhere near as accurate as my rifle's favorite load (8.0 of lil gun over a 208 amax.)

I won't go so far as to say the Remington factory subs suck, but they ain't good - and that has been true of the 2 300s I have shot it through.

Groups will (sometimes) open up if you optic is too low power or too high power, which is why I ask about the optic.

And were groups from bench, prone, or off-hand?

Were the rounds evenly distributed in the groups or were they stringing? Did they string vertically or horizontally?

Lastly, you mention accuracy of the other guns was good, and I bet all 5 others were supersonic. Be aware that small changes - in anything - shooting a subsonic round equal big changes in point of impact. It ain't a fair fight to put a 308 next to a 300Whisper and compare accuracy. Once the 300's favorite loads are established (and how did you break in your barrel?), results should improve.