It seems to be but It will take more time and more shooting to know for sure. The rifle definitely shoots well and the stock seems to ride the bags straight. As long as I do my part by not touching the rifle and shooting totally free recoil it will do it's job and shoot tight little .250"-.300" 5 shot groups at 200 yards. The stock was probably built in 2013 or 2014 so I'm not sure when McMillan started using the new fill or if it is in this stock at all. I usually try to use laminated wood stocks for that very reason. I've got another Dasher being bedded by Alex Sitman at Master Class Stocks right now into a PR&T Low Boy laminated BR stock and I'm hoping that stock doesn't transfer unwanted vibrations into the barreled action. We'll see.How is the vibration in the ST-1000? I spoke with Kelly at SW nationals and he said they made a new fill for the stocks to cut down on the reverb. Is it stable and quiet ?