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Do you absolutely, positively, need an aftermarket barrel? Otherwise this means you're looking at either a standard Model G-34 or G-35. Both are excellent long-barreled pistols, respectively in 9mm or 40 S&W.
If you want something slightly smaller that could also serve you as a typical everyday carry pistol, then, you have another choice: You could buy a standard Model G-17. Then get an extra, Lone Wolf, +2 inch, extended and ported barrel for use around the farm.
In my opinion, of the two calibers you've mentioned, 9mm FMJ bullets would be best for what you're going to be shooting at - especially if you plan on eating anything you shoot - and you can't get centerfire ammunition any cheaper than 9mm!
I know this is the Glock forum; but, I can't help wondering what you might think of a SIG, 'Mosquito'? Here's a picture of their 22 caliber target package: