CZ have produced the "Battue" in 7x64 with a 20" barrel, there are several other european manufacturers who make a 20" barrel model too. I think a 22" would be my favourite to give the best compramise and to still be handy, if it's not going to be threaded. Just my unprofessional personal opinion.
The reloading manuals, and a certain Mr Hawks mentions this, say that the 7x64 likes the longer/heavier bullets because of it's throat. I'm not sure but I know someone who uses a 7x64 with 140gn BT's on fallow to great effect, then swaps to 162gn Swift A-frames for boar. It works!
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