It appears to me he's getting the same results I've gotten for years I've tried a lot of different ammo in many different rifles and I've seen group sizes just about the same as his. From what I read in this forum, he's also getting almost identical results BR shooters have been getting for years with their rifles. That Walther rifle (which can be bought in the USA) will probably be the equal of any benchrest rifle and could be shot from a bench perfectly well if put in a benchrest stock. It would also cost about the same as most currently used BR rifles.
Some are criticizing the statistical methods he using but for the results as presented they are just fine. All that nonsense about control of air conditions and bore cleaning is also just some poster trying to bring into this a lot of factors that really would add very little, probably nothing, to the results, Really, this guy is just confirming a lot of data we already had and there is nothing wrong with this.