I put together a 8.5" to tinker with after messing around with a 16".
It left a lot to be desired for where i hunt. Fun shooting subs but those don't kill well at all. Ended up just sticking to a 12.5" 6.8 as i can get 2790FPS with the 85gr Barnes and 2775fps with the 90gr Speer TNT Varmint and they both shot really good, even took a yote at 420 yards with it and the 90gr Speer with awesome carnage.

Ive tried the 300 a few times and just cant jump on that train.