Who know maybe we'll see adjustable LOP Bullpups, the Tavor's LOP for example is fine for me even with a couple inches of clothing.
Clothing sure, what about body armor and webbing, what about the 5'2" guy or the female in the unit? Winter clothing and armor??
Same goes for adaptable systems for lefties. Adding more parts to the logistics chain only adds room for error. You break a lefty bolt and the unit armorer only has right hand bolts. Issued kit is all uniform for a reason.
FN F2000 or the P90 are examples of fully ambidextrous bullpups
the diff between 10.5 and 20..... sure still hurts from either one but you got a lot less chance of hitting what your shooting at 300yds
At 300 yards are you going to expose yourself on the pretense that the enemy is only running 10.5" barrels and won't be able to hit you? No one will know the skill of the shooter, what length of barrel or weight/style of bullet is being fired at them. Again, I never said I would run a 10.5" or suggest running one as an all around length. There's many soldiers kicking doors with an M249 SAW. The length issue is moot when comparing a 14.5" carbine to the 20" bullpup.
A 10.5" barrel running the heavy and effective 77gr Mk262 round is pushing 2363 fps which is in the ball park of 123gr M43 7.62x39 which runs around 2329 fps from a 16" barrel. If we consider the M855 62gr FMJ being issued the velocity from a 10.5" gun is 2639fps. With the aid of an online ballistics program we see that the drop at 300 yards is as follows.
(both calculations were done with a 50 yard zero)
5.56 62gr 22.7 inches with 298 ft/lbs
7.62x39 123 gr 32.9 inches with 417 ft/lbs
I'm sure no one has ever made reliable shots at 300 yards with the 7.62x39 round.

With come ups, hold over, or adjustable sights shots to 300 are very doable with both calibres. in the configurations above.
TDC