Bunn, 20, had a loan stint with Crewe last season.
The striker was snapped up by the Blades yesterday before the summer market shut.
For the big stories and the banter follow us on Twitter: @tribalfootball
Tribal Football Staff are dedicated to the football tribes from all over the world. Our team is passionate about delivering football news to our hundreds of thousands of followers in all the corners of the globe. Football is life, It never stops, Neither do we.