I have tried only one hardness tester. I won't say which for fear of getting sued. I got wildly different readings from the same batch of bullets. But why complicate life, when alloy hardness is so easy. All you have to do is get the alloy mix right. Any particular mix will have a specific hardness, which will be the same for that mix, every time. I have those hardness figures somewhere, but they will be in any metals handbook.
There's nothing special about the 40S&W, it is just another calibre, quite similar to the 9mmP in chamber pressure and MV. 6% Antimonial alloy is the cast bullet industry standard for handgun bullets, and is good for 1300 FPS in any calibre. You don't need to know the Brinell hardness, you need 6% antimony in your alloy, that's all you need do, and forget the hardness testers. How much simpler can it be ?
I'm a commercial caster, and need to cast very consistent bullets day in, day out. I have a bunch of very satisfied customers who shoot my bullets from every imaginable type of firearm, without significant leading or other problems. Including Glocks. There's nothing special about Glocks, you can ignore all that BS about cast bullets being a problem with Glocks.
You can also safely do without aftermarket barrels. They are not available in South Africa, and several of my customers shoot cast bullets in the factory barrels of their Glocks, including the 40S&W.