In choked barrels I've found the smaller diameters work better for power, ease of loading and often accuracy. I run the heaviest slug I can reach 900-980 fps with.
The fastest I could push the NSA 17.5 gr. out of the Hi-lite was 885 fps with the reg at 155 bar. The 17.5 gr. come in only .2165. The .217 20.2's would do 845 fps.
Remember to seat them. If you don't they can walk out of the back of the mag when you cycle them and become misaligned and jam on the way back in.