You cannot test the team of a ShulkerBullet , try /execute @e[type=ShulkerBullet,team=R] on a shulkerbullet which is in the team "R".
It won't work.
Short summary: Cannot testfor team on shulker bullet
MC-89773
Cannot testfor team of shulkerbullet
Resolved
Duplicate
0
Luca von d. W.
(Unassigned)
Community Consensus
Minecraft 15w40b
Retrieved
Related to MC-89323.
Can confirm for all non EntityLiving entities.