Your Sig is one of the best combat/SD weapons ever made. Have it's little brother, a 228 that I use for IPSC matches and it has NEVER bobbled in what has to be way over 20K rounds. Did a 3k rd torture test on it and it wouldn't quit shooting. Only thing I did while doing the test was brushing the rails every 1k rounds.
The 17 is one of the best .22 caliber revolvers ever made and extremely accurate. The new 617's are nice but don't have the class of a well maintained and blued 17 IMO.
If you'll be shooting the 17 and love getting enjoyment from 1/2-1.5" groups sandbagged at 25 yards all day I'd say go for it!
Since you've got you bases covered with the H&K (great weapon) I'd be all over that 17. 226's are a dime a dozen. Love mine and it will shoot as well as my model 41 target pistol. Head shots on squirells (sp) and rabbits are very doable if you're into hunting with a handgun like I am.
Go for the 17, don't look back and shoot the heck outta it!
Don't forget to let us know about your decision when you have the 17 in your mitts
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