I know of sniper schools that encourage students to cut the barrel on their own rifles. When lives are on the line... why wwould anyone risk making their rifle less accurate... unless they truly saw a difference in accuracy with a shorter barrel.
Please tell me you've seen the video of Travis Haley shooting a 9", suppressed, 300Blk at +750 yards.
Long barrels are sooooo 1985. Metallurgy and technology build barrels a lot different than they used to.
Velocity only helps against wind and humidity... When there is a lack of either of those factors... Two barrels, of the same design and quality, but of varying lengths, the shorter wins.
This all goes back to the pencil test. Take a standard pencil, and break it. Now break one of the pieces. Then try to break another one of the pieces. Every piece, as it gets shorter, gets harder to break.