M16 shoots with resistance?
 

My guns shoots stedily but sometimes it fires with some resistance.What could be the problem with my g&g m16

Define resistance?

re·sis·tance
n.
1. The act or an instance of resisting or the capacity to resist.
2. A force that tends to oppose or retard motion.
3. often Resistance An underground organization engaged in a struggle for national liberation in a country under military or totalitarian occupation.
4. Psychology A process in which the ego opposes the conscious recall of anxiety-producing experiences.
5. Biology
a. The capacity of an organism to defend itself against a disease.
b. The capacity of an organism or a tissue to withstand the effects of a harmful environmental agent.
6. Electricity The opposition of a body or substance to current passing through it, resulting in a change of electrical energy into heat or another form of energy.

Shot in the dark but I've heard some people describe it as resistance when the hop is set too high, causes an unhealthy "springy" sound from the mechbox. I think it's from the nozzle having to push the BB past the hop up rubber?

All I read...