...IMHO, barrel length is mostly a matter of personal preference.

FMIW: I have two .416 Taylor rifles. Both are built on Pre 64 M-70 actions. One has a 24" barrel, the other rifle as a 25" barrel. The velocity differential is barely negligible across the screens. The load(s) are designed for 400gr bullets at 2380'/sec. I've used the combination of rifles/components in Africa on numerous occasions, with temps in the upper 90's, and have never had any problems. Viz; extraction/pressure/accuracy.

Good luck with your project...I trust you'll enjoy the Taylor as much as I.

Hunt hard, life's short