n9nwo Wrote:The 300 BLM (7.62x45) seems to like shorter barrels where the 5.56x45 really needs a barrel longer than 14".
That is where the 300 BLK stands out is its love of shorter barrels.
The reason why Blackout 'seems to like' shorter barrels is because you don't get any more meaningful velocity out of barrels longer than 16". The pressure drops in a large 30cal barrel quickly. This is why manufacturers only sell 16" and shorter. Anything less than 16" however is just your normal less-velocity-per-inch.
A 10" barrel in 5.56 is long enough to be an effective, compact weapon. Below 10" and it arguably starts looking as effective as a 9mm SMG. Both have their roles but if you are looking for maximum effective stopping power in a compact rifle then 10-12" of 5.56 is powerful enough to 200M. Depends on your definition of compact of course and also depends on what you value more; compact or effective? More effective = less compact, More compact = less effective.