Re: Full contact of rifle butt with the shoulder
In the context of the rifle above, especially in a combat situation, the unsupported standing is the last shot you would want to take.
People practice it because they see it done in other regards, but really it should be only used as a last resort or in a very close in snap shot situation.
Using an 8LBS M4, different story, you can make shots standing all day long, a 15-18LBS sniper rifle with a high powered telescope on top, not so much. At least you can't compare the two the same way, like driving an 18 Wheeler tractor trailer vs driving a Ferrari. Sure both are standard shift and move the same but how you maneuver the truck through traffic is not how you drive your Ferrari.
Sure given time and opportunity, you can build a decent position, get some hits on an 18X30 inch target from 400 yards, but it's not fast, nor is it effective, when you think about the time it takes to build the position. In a combat / tactical situation you would be better off finding support than attempting to "build" a successful standing position. Which is why you see snipers even on the battlefield using a partner for support. In fact partner supported shots from the standing are taught much more than unsupported standing.
Practical
Posing
In Sniper School, they never had us take a standing shot. In classes of late, the only standing shots taught are snap shots for targets that are immediate and close --- example you come around a corner and 25 yards out you have a threat and the only rifle you have is your sniper rifle.
We do this because we have seen it done, not because it was practical to do.
We do this in certain competitions because time and opportunity are plenty, as noted with bullets flying past from a guy with a full auto AK, you don't want to stand there, and build a position. You have a bolt gun in a machine gun war, so cover and concealment are your best friends.
So consider the use, and the practical application of the task before committing to the idea that this will work anywhere but the square range in your home town, there is no time and opportunity anywhere else, that is not smarter to seek support and cover.