Flamerush

[Avnger345]

If I am attacking with 2  {Flamerush Rider}   Can I copy each other. And then when the copy comes in and is attacking with that let me copy again?  Infinitely?

[Remillo]

Flamerush Rider's ability only triggers when it's declared as an attacker using the special action at the start of the Declare Attackers step.  Being out on to the battlefield tapped and attacking means it wasn't declared as attacking, so it won't trigger.