According to HKParts, they are different.
"New HK USP 9mm Tactical Recoil Spring With Buffer Assembly Complete. Great spare or replacement item to have as a spare. This is the factory part. This recoil rod assembly was designed to be used for heavy use with a sound suppressor attached."
However, I haven't heard a concrete answer to how they are different.
http://www.hkpro.com/forum/hk-handgun-talk/119356-usp-tactical-recoil-spring-vs-regular-usp.html
I can see how a heavier slide along with a suppressor may require a weaker spring.
"New HK USP 9mm Tactical Recoil Spring With Buffer Assembly Complete. Great spare or replacement item to have as a spare. This is the factory part. This recoil rod assembly was designed to be used for heavy use with a sound suppressor attached."
However, I haven't heard a concrete answer to how they are different.
http://www.hkpro.com/forum/hk-handgun-talk/119356-usp-tactical-recoil-spring-vs-regular-usp.html
I can see how a heavier slide along with a suppressor may require a weaker spring.
