Good tube, plate, and nut. buffer and spring were too much. - Aero Precision M5 .308 Carbine Buffer Kit

After attempting to shoot 4 different kinds of surplus military 7.62x54 ammo and 2 kinds of retail .308 Win ammo I could not get my rifle to feed or even eject using the spring and buffer included in this kit. Exact specs are not listed anywhere on the website or on the box but the buffer weighed almost double what my other .308 buffers weigh. I'm guessing its a 5.6 oz. buffer? I'm not sure. I never weighed it. But also the spring was about twice as stiff as any other .308 buffer spring i have worked with. I was able to get it to fire properly after cutting the spring a couple times until it was only about 1" longer than the buffer tube. However this caused the bolt to not be held tightly in the breech to the point that tapping the butt against the floor opened the bolt about an inch. I considered this a defective rifle at this point and ordered a 3.8 oz. mil spec .308 car buffer from a different manufacturer as well as a cheep .308 carbine buffer spring. I installed these new parts and the rifle worked fine without modification. The problem might have been that this was a DPMS LR-308 build rather than an Aero M5 build, but I was under the impression that the Aero M5 is based on DPMS LR-308 and that these parts were interchangeable. I may be mistaken, however I do know that these parts did not work in my rifle. The buffer tube, end plate, and castle nut were all very well made and are still on my rifle so this kit was not a complete waste of money.