...400 meters. How well documented is this tactic as opposed to 300 meters or 600 meters?
Hard experience--wherein YoungSon experienced/had to overcome it multiple times.
He was quite specific and spoke of it repeatedly. (And as FiST Team leader, he was
the one that had to deal with it while his company was getting shot up.)
I know that the Mk 262 is developing a good reputation for precision engagements at this and longer ranges...
Here is the comparison of the improved M262 against (the likes of) the Grendel.
Mk262 ballistics courtesy of the manufacturer/Black Hills
I cannot speak to the field performance of the newer solid penetrator/M855A1 except to
say there is a great deal of back & forth discussion of it in the Graduate forums,
and to offer this briefing...
...noting the "Green" aspect as the touted headliner. That it also penetrates well out
to 300+ yards seems an added benefit--incredibly so. (Think what a 6.5 could do with this bullet design)