The cUAC-20 is great for pounding away on slow moving assault mechs and it does pretty good against light mechs because of its 5 round burst. Spray and pray. I chose a pair of medium pulse lasers because I like their shorter duration time. Focuses the damage a little better I think. A six pack of short range missiles round out the up close punch. Use the Summoner's speed and maneuverability to get into range and open fire with everything you got.
Because you already have it as a link. Please see the FAQ section. I will fix this for you on this one.
If I went with regular medium lasers I would get a mk1 targeting computer instead of Artemis. The leftover ton I would split between more ammo and armor. But for me, I like the medium pulse on this variant.