Imported object scales itself down when rotated

I imported a spartan from halo reach, however it did not come with a rig/armature thingy(im new to this). I made one using a youtube tutorial and I connected the head bone to the head, however when i switch to pose mode and rotate it around the head shrinks, how do i get it to not shrink?

Don’t double post!

You have asked this question twice - wait for your post to be moderated until such time as you have posted 10 meaningful posts please!

See my answer in your duplicate post.

Cheers, Clock.