I tried one and wasn't impressed. Plus, it seemed to not let the slide fully return to battery if you slowly let the slide forward when manually cycling the pistol. Just an observation. Never caused an issue, but I was glad to go back to the OEM guide rod/spring.
I used to have one for my 9 mm. Sorry for the Sprinco guys but I definitely did not like it because :
- the rod obviously was designed for the .40 with the somewhat longer slide (compared to the 9 mm's slide), leaving the front of the rod protruding out of the slide (not a great sight)
- as for the "recoil reducing properties", I could not ascertain or feel any improvement over the original guide rod (I admit this is a subjective assessment)
- after a couple of shots fired, the guide rod looked like being ran over by a truck. As a matter of fact the steel rod slammed against the inner edges of the rod passage hole in front of the slide every time the slide went back into battery (not to mention the damage this could could have done to the slide)
In short, I kicked the damned thing out of my gun and went back to the OEM guide rod. Nevertheless I feel a bit sorry because the idea is not bad, the rod was a nice piece of craftmanship, well machined and finished but the concept clearly was not worked out properly for the P99. I would provide a plastic buffer (like the one found on the H&K) and solve the problem of the disalignment of the rod by adding a guide sleeve of bushing.
I installed one not for it's recoil reduction (not much if any), but since my original plastic rod was bending more than I liked. I just wanted a steel guide rod. I'm happy with it for that purpose, but generally not worth what I paid for it though.
I have tried two different Sprinco springs in my old 1998-manufactured P99. The first one did not work at all, as the slide frequently failed to return to full battery, so I discarded the assembly.
A few months later I acquired some high-pressure ammunition, and wanted to avoid beating up the gun, so I ordered another one. This one worked, with both regular and carry ammunition, and did a good job of taming the recoil of the higher-pressure carry ammunition.
A few months ago I acquired another P99, this one a 2005-manufactured P99QA, and I wanted to get an assmembly striclty for use in this gun. I have contacted the proprietor and he told me that I might be waiting a while for this, since a subcontractor that does some of the machining has been out due to medical issues.