Colossal Fighter x 2 + Armory Arm

Opponent has a Caius
I have 2 Colossal Fighter and 1 Armory Arm

I equip Armory Arm to his Caius. Caius become 3400
I attack with my First Colossal Fighter and it dies, I take 600 damage.
I do not wish to activate Colossal Fighter's effect so it stays in grave and Armory Arm burns for 2800.
I attack with my Second Colossal Fighter and it dies, I take 500 damage.
I activate its effect to special summon Colossal Fighter 1, Armory Arm burns for 2800 from Colossal Fighter 2.
I repeat the cycle until he dies.

Is that legal or is there some ruling that does not allow this to happen?
I know that in OCG the 1 Colossal Fighter 1 Armory OTK doesn't work anymore but will 2 Colossal Fighter and 1 Armory Arm work?

Thank you.

2 colossal will work as long as u target the other colossal fighter
for example
colossal #1 in grave
colossal #2 is on field

when colossal #2 attack and die, u must revive colossal #1 to burn.

colossal have to be in the grave during resolution to cause opp the burn