I pulled a couple of buffer springs out of a couple AR15's that I had sitting around, out of curiosity, and they were at least a full 2 to 2 1/2 inches shorter than the one for the MP 10. Suprisingly, the MP 10's buffer felt and looked very similar to a H buffer. I sold a DPMS .308 before purchasing my MP 10 and if I remember correctly the DPMS had a shorter buffer. The buffer spring on the MP 10 even seems slightly heavier.