Blast... couple of comments on the Holosun 507 and 510... both have a solar cell that helps(or fully) powers the emitter in addition to a 2032 cell.. in bright ambient light the solar cell will intensify the dot

... it is possible to set up either with a "shake awake" function that automatically goes off and immediately on...

there are 3 options to the reticle... a circle, dot, and circle + dot

the circle on the 507 is considerably smaller than the 510... on my 507c v2 the dot is 2moa and circle is 32moa
on the 510c the dot is 2moa and the circle is 65moa

the 510 is large, but the large view window makes tracking targets for Steel Challenge much easier for old eyes