Luo Xingyu's gun was the best.
Why was Luo Xingyu's gun considered the best? Because among guns of the same model, there's a difference in precision, and Luo Xingyu's 95 machine gun was selected for its highest accuracy out of twenty such guns.
Moreover, Luo Xingyu's machine gun was also fitted with a scope, a brand-new one, used with the 88 sniper rifle.
Now Luo Xingyu had a machine gun whose accuracy was not at all inferior to the average level of the 88 sniper rifles. It could fire in bursts or single shots, had a larger magazine capacity, and was a bit more portable, so why would Luo Xingyu need an 88 sniper rifle?
However, Luo Xingyu didn't use her primary gun when practicing shooting because barrels and scopes have a lifespan. Typically, after firing two thousand bullets, the scope would become inaccurate and need to be replaced.
Therefore, when Luo Xingyu trained, she used other guns, as there were plenty here.