Bruce Owen, former production manager at Purdey wrote that with the advent of CNC machines work has become more accurate, and steels used upgraded due to CNC machinery needs.

So if in the past Purdey made "best" guns, can we say that in the CNC era they have upgraded to "bester"?

As for best being English by definition, the poster has not examined high grade Darne and Ideal, or Rizzini Fratelli, Fabbri, Desenzani, Bossis, Perugini Visini and the list of names ending in a vowel can get long.