If you're a member or guest, BLGC allows 50 cal and we have a 600 yd range. I think our only large caliber "rule" is not shooting high power under 100yds (there's only one or two 50yd rifle ranges) and no incendiary. No steel when it's hot/dry.
It's a hike, 46 miles for me from Parker. Pawnee is a bit further depending on where in Denver you're coming from.
I think we're back to wait list status @BLGC, but worth looking into. Super cheap dues.