If you're shooting 1400 and occasionally a mile, you might be happier with more magnification on the top end than 16-20. The ZCO 527 is only about 3 oz heavier than the 420. If you could find a Minox ZP5 5-25, that also would work at 34 oz and it's a superb scope.
I have a SB 3-20 US on my...