I've got the "big dot" on a 40C. Bo (at XS) told me that they didn't have room on the rear for the tritium vial. I'm not sure I agree....
OTOH, it works well enough. The "night" situation, where there's no tritium on the rear sight really comes down to seeing where the rear sight occludes the front dot....
But, in all honesty, IMHO, night sights are for some very rare situations where you can see the target, but not the sights. The rear tritium would likely be an advantage....
(I have a couple sets of "small dot" on other guns, including tritium-vial-equipped rear sights. Quite a bit better, within the limits I mentioned in the previous paragraph.)
IAC, the big dot front sight makes it an SD gun. Six rounds into a six-inch circle at 30', more or less, is what you're trying to do. Paper punching is a waste.... The small dot front sight is only slightly larger than a decent front sight, and doesn't really cause issues for me for paper punching. It's not as quick, but the end result is that the overall feel is enough like standard sights - night or not - that the transition isn't a major change. Having that golf ball out front on the 40C is a little jarring

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Regards,