I searched for buffer spring rates and never found a real answer, just some manufacture estimates of relative percentages. So, I measured some of the springs I had laying around and calculated the following spring rates.
Carbine (oz/in):
- Damage Industries Chrome Silicon: 25.3
- Brownells Chrome Silicon: 26.0
- Ruger MPR Take-Off: 28.0
- Sprinco Yellow: 23.3
- CMMG: 26.1
Rifle (oz/in):
- Damage Industries Chrome Silicon: 21.9
- Brownells Chrome Silicon: 23.1
- DPMS Take-Off: 23.8
- Aero Precision: 20.8
Carbine (oz/in):
- Damage Industries Chrome Silicon: 25.3
- Brownells Chrome Silicon: 26.0
- Ruger MPR Take-Off: 28.0
- Sprinco Yellow: 23.3
- CMMG: 26.1
Rifle (oz/in):
- Damage Industries Chrome Silicon: 21.9
- Brownells Chrome Silicon: 23.1
- DPMS Take-Off: 23.8
- Aero Precision: 20.8