What is the best airsoft semi auto assault rifle?

If you asking about different models then it all depends on what you perfer.For example, the most common are AKs and M series guns and i myself perfer the m16a1.But if your asking about brands KWA,...

The one you can afford.

Ruger 10 /22.

I myself have a savage 64 semi automatic, and i lubricate it with break free oil you can find it at any sports store.

You get what you pay for.