In the 1999 anime, bullets were seen bouncing off his body without leaving injuries. His sturdiness, however, is inferior to Uvogin's. If it is enforced with Ten or Ren is unclear. However, in the 2011 anime and manga, after his fight with Nobunaga, he sported some bruises.
Pike's body is very sturdy. He took a beating by Pokkle with the Hunter strengthening his punches with aura and, despite not being able to use Nen, he was barely grazed. Even Shizuku, despite landing 29 blows of her vacuum cleaner, which could kill a Nen user in a single swing, caused him superficial injuries, which anyway led to his defeat.
After receiving a ball powered with Nen from Gon, he seemed to receive minimum damage from the impact. Furthermore, being hit in the face by Goreinu's sudden throw did not even stun him for an instant, although it did leave him with a bruise.