Are you on crack? The guns on the N1K-2 are outstanding, and its turn rate is fantastic. The only things really bad about it are speed and climb rate.
The N1K-2 has Type 99-2 cannons. Ballistically they are comparable to the German MG151/20, the standard gun on most designs. It fires a slightly heavier round at a bit higher speed. The gun suffers a bit from firing at a very slow ROF of 8 rounds per second, MG 151 has 12 and the Ho-5 (Ki-84 & Ki 61) 14.
But it'S climbrate is far from being bad. Not many planes in Ah2 are capable of achieving a constant climbrate of more than 4000 fpm (sealevel up to 5k) (for comparison: Ki-61 just over 3000 fpm, Spit XVI about 4600 fpm). In a dogfighting situation you may notice N1k's hanging on their props like no one else.
The N1k doesn't climb bad, it rolls badly... that's it's biggest weakness in my opinion.