Gun length, propellant burn rate, and barrel wear

Would a higher propellant burn rate give a gun greater velocity without increasing barrel length?

It can, but faster burning increases rifling wear and may prevent consistent projectile spin, so higher velocity can carry an accuracy penalty.

A faster burn can give a projectile higher velocity in the same barrel length, but it also increases rifling wear. The shell may fail to engage the rifling consistently enough to acquire the intended spin. At long range, small deviations across several parts of the gunnery system can combine into wide dispersion. Italian accuracy problems illustrate why a cumulative explanation can matter more than blaming one component. Jellicoe's repeated pressure on the British armaments industry is credited with reducing comparable quality problems.