ATTENTION! 
We have had a few customers have an OOB detonation do to cutting an HBI buffer and using it in place of the factory buffer. The ONLY advantage to that during our own personal testing is the bolt action is slightly quieter. It does nothing to reduce any actual additional recoil.  
 
1st: During testing I have found the spring works its way into the soft rubber material which then causes the secondary spring to wedge in between the factory recoil spring which then does not allow for the bolt to fully close during the next shot. 
 
2nd: Because the HBI buffers soft compound The spring itself causes slight expansion on the OD of the buffer so it can NOT move freely as it needs too. 
 
3rd: The spring can bind up in the receiver itself from the added expansion & as it expends even more from oil and heat. The rubber also expands through the spring coils then bind to the recoil spring itself not allowing the bolt to fully close.
 
4th:  BE SMART.. Run our kit it how its designed to or run or don't run it at all. 
 
As the FIRST in the industry to develop a short stroke damper kit for the Stribog's & Unlike our competitors I took 30 years of experience tuning  shocks for some of the fastest desert racers in the world and applied it o the Stribog SP9a3! Introducing the 1st of its kind 3/8" to 1/2" shorter stroke recoil damper kit!  Since Grand Power release the 3000 plus serial number Stribog SP9A3 delayed blow back with the US Bolt lock system, recoil hasn't been much better then the SP9A1 which was really disappointing.  I spent countless hours applying my shock tuning skills to the recoil system trying different rubber compounds, secondary rate spring set ups in 19 different rates and configurations only to end up with sub par results that were not worth calling a product.   In the end we were able to find a real solution to completely bring the felt recoil back down to the level of what a delayed blowback should feel like.  Even with high powered ammo) it will give you HANDS DOWN the softest, flattest shooting, and because of the shorter stroke follow up shots are much quicker!  The only thing you feel is the energy of the round much like a higher end PCC like an MP5. 
 
This kit was designed using a Factory SP9A3 & SP9A3S with the factory Stribog lower & bolt stop & trigger. Customer also use it in aftermarket lowers and in the SP9A1 Gen 2, but because the bolt is heavier it will not perform as well as it does in the SP9a3, but will out perform any other option out there!   It will NOT work or fit with the dual recoil rod SP9a1! Note: Due to the slow down of the bolt you will notice that the bolt release just slightly harder to release when the bolt is locked back. This is 100% normal.  
 
New Stribog's beware! Newer Stribog springs seem to have a slightly larger diameter recoil spring than the older models. From testing I have concluded its just a thicker coating than before. After installing make sure the buffer can move to the rear somewhat freely while compressing with your hand, and release freely. If it is tight you will need to lightly sand off the coating on the factory recoil spring just on back end where the secondary spring sits.  If you don't feel confident you can send in your recoil spring assembly and I will do it for FREE. You just have to pay to ship it to me, and pay to ship it back. 
 
SP9a3 & SP9a3S Aluminum 2 Stage Damper Kit (This can be used without the pad for a 3/8" shorter stroke or with the pad for a 1/2" shorter stroke)
 
Includes:
-One 3/8" CNC Machined Aluminum Spacer/Recoil Spring Carrier for 2 Stage Damper
-One Pad To Convert To 1/2" Stroke  (Note: Its 100% normal for these to flex when installed)
-One Secondary Rate Spring
-One Washer
 
Installation:
1st & If needed take a scotch bright pad or light sand paper and sand just the outer coating on the stock recoil spring. On older versions you never had to do this, but on newer versions you might. 
Slide the stock buffer over the recoil spring.. It should move freely
 
Disassembly & Install Instructions
Disassembly:
Compress factory recoil spring
Remove spring cap and guide rod (Be careful! The Hollow rod is very thin & weak!)
Remove rod assembly from factory buffer and remove the little black washer inside the buffer
Remove the step down spacer from the stock buffer
Press step down spacer into 3/8" spacer
Re install guide rod (Be careful!  The Hollow rod is very thin & weak!)
Install the new washer only as you will no longer need the small black washer 
Install the pad for 3 stage set up & 1/2" Shorter Stroke (Leave out for 2 stage and for 3/8" Shorter stroke)
Install the stock recoil spring
Slide secondary spring over the recoil spring all the way up against the the 3/8" spacer
Slide the factory buffer over the spring making sure that the larger deeper side of the hole faces the secondary spring
Once you slide it up against the secondary spring compress it all the way against the spacer to seat a portion of the spring into the stock buffer
Compress the recoil spring, then re install the guide rod end cap (Easiest way is to make sure the guide rod is fully extended then hold the buffer up against you chest in a slightly downward/horizontal position before compressing the spring. This allows the rod to stay extended so that you aren't fighting to compress the spring)
If you need any more assistance feel free to email me at kdgunwerx@gmail.com