I handled several recently. A .375 H&H and a .404 Jeffery. Fit and finish was top notch, among the best that I have seen. The stockwork was exceptionally good, as was the metal finish. The action cycled like a custom rifle should even though the Heym Martini is a production rifle. I was able to to compare them to custom Martini rifles in .375 and .280 at the same time. The factory rifles compared favourably but I preferred the real thing....although it is higher priced.
the Heym Martini rifles are very well balanced and point extremely well....despite the heavier weight of 9 to 10 lb unscoped. The design of the Martini stock in the British Best Rifle flavor is a big factor. While handling these rifles, I met and spoke to a couple who had experience shooting them. She took her big game with a .416 Rigby I believe.
I want one in .375 H&H myself.