https://www.primaryarms.com/Primary_...0red%20dot.htm
This is what I affixed to my 15-Sport.
The Primary Arms M3 Clone with a high cantilever mount. The 3MOA dot is OK.
If you want to add a magnifier later on, you can add on a Primary Arms 3X magnifier on a side swing or QD mount as seen in this pic:
You should also check out the Primary Arms micro dot on a QD mount.