12"L on Guam give you 6 binds......

14"Ls give you I believe 1 Bind on the guam.

You can't put on 14Ls with any significant amount of ammo. 12" allows you 4 binds.

It's a pretty marginal range difference -- a tenth of a tic at most. (overshadowed by
at-level spread issues, especially for the 14" guns) That said, the Guam cannot mount the
Mk 10 L with ammo, and the 12" guns hit harder per shell at max angle.* It's unclear to
me that the speed advantage and lower angles (better for rushing) outweighs the lack of
firepower.

*Just try to keep ships there. The dead zone for 12" guns is *painful*, and can result in
you getting killed by a CA.

Follow a BB5/6 closely (not too close that you cross it), and do AAing as well as
hunting down smaller targets. Also, I
recommend you put 12" Ls instead of 14" Ls if you are not doing so, because the
12" Ls have longer range than the 14".

Unfortunately, the lack of range for US BB1 (and your limited overheat time at-level)
makes exploiting blinding opportunities (which aside from counter-rushing should be the
main time you attack) very difficult. Stay close to the line, make sure you've downed all
the enemy planes, and hope that there aren't any subs nearby.

You can mount 6"/47 D guns for AA, so you may want to use their long range and high
firepower. Also, you have lots of scouts (more than you'll see again until the Montana).
At worst, you can be a glorified AA boat, covering your team's BBs with AA fire, and
lighting up enemy ones with your scouts.

LKs guides are right on. There is no other way to play with that ship. Mount your
AA and support the larger bbs by taking out subs and ff-ca class ships. You are the
FF of BBs.

Learn when to ninja, such as when the enemy is blind, or when there is a heavily
damaged bb that needs one more hit to sink it. Blind the enemy with your AA.
Thats why you have it. Its a long grind, just stick with it.