I was the mug - because I did plenty of culling - who was given a consignment of Grandslam by Speer in order to see how they perfomed on red deer and calves. I had been in touch with Speer regarding their boat tail bullets in .243 with which I was unhappy, and was asked if i would like to undertake the task. This was when the Grandslam in .243 were developed after the larger calibres were found to work OK.
I worked up reduced loads, then full powder loads - 'found that they liked the same amount of RE19 or 22 as the other 100 grain bullets I used at the time - namely Norma semi-pointed soft point and Speer soft pointed, boat tail spitzers, and later the Speer round nose 105 grain.
The grandslam had it's first kill on an early morning foray when I spotted Charlie heading off home. He just dropped. For a hill fox he was far enough out that he didn't spot me before I did him. I was lucky.
A couple of weeks of hinds and calves passed and I was able to let Warren Cloninger - Speer's ballistician at the time, know of my findings. Warren was a good bit older than me so I don't know if he is still in the 'land of the leal', but he was a nice friendly fellow and sent me a signed, updated version of the Speer handbook.
Personaly:- Grandslam do work. However, the cheaper and cheerful bullets in Speer, Sierra and Hornady kill extremely effectively so why waste your money on more expensive stuff unless your barrel DEMANDS some specific brand and model in order to stabilise them.
I know of a .243 barrel, hand-lapped by Shilen, which was removed from a brand new rifle because it would not stabilise the various bullets available to the shooter.
It was later put on another rifle and it was found by trial and error that it would only accept RWS 100 grain.
It was before this when Norma went through a bad patch with their .270 ammo. They had been taken over by RWS and things seemed to change.
Then the .243 ammo began to alter in characteristics and I got in touch with their ballistician who was a very amenable sort of bloke. We corresponded about the hardness of jacket alloy and core, and a consignment of their new ammo was sent over for testing. I wrote endless reports - no typewriter for me in those days - and a fairly satisfying result was achieved.
A part of the problem was that the alloys were much the same but the characteristics of the powder had changed. There was a world shortage of egyptian cotton so other, cheaper cottons were imported in order to mix with the nitro chemicals and produce an extrudable compound.
This changed the powder burning efficiency.
It was significant that at the same time, the quality of waxed cotton cothing changed. Not for the better.