Brief update...

I wrote to ADI and asked them about H4895 (called AR2206H here) in the Fireball. Their response was non committal but not discouraging...

Thank you for your enquiry of 26/6/2018 with regard to reloading using ADI Sporting powders.
Please find attached our latest test load data for .17 Remington Fireball.
You may be able to develop a load for this cartridge with AR2206H however you would have to undertake your own experimental load development. We do not have any test load data for .17 Remington Fireball with AR2206H as it is considered too slow burning for optimal performance in this cartridge.
Extreme caution should be taken and loads should be worked up accordingly. Refer to our website at www.adi-powders.com.au or our 9th edition handloaders’ guide for more information, warnings and reloading safety.

In the meantime I just took the rifle to double check zero at 125y, at which range I wanted to have it printing 2.4 inches high. The groups at left and right are the 25g Vmax with H4895, the lower centre group is the 20g Varmageddon with H4198.

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I adjusted the zero up between the far left group and the far right. Pretty pleased with this accuracy with H4895 given my coarse bench rest skills and apparatus. About 0.45MOA.

Not so thrilled with the H4198 accuracy but that particular group was larger than usual. Nice that they print to roughly the same spot though.