If in doubt, get a small quantity to try.
The link was to loaded ammo, and it is minor. Are you talking about buying loaded ammo or bullets then loading your own ammo? I would be curious what powder you would use for 150gr 9mm bullets to make major in a factory Glock barrel.
Is this IPSC? 9mm major means Open, right? I would worry more about running against Open guns than accuracy, especially if you want to improve classification.