Just thought I share my current build, because there is not a hole lot of info on GBB SVD's. And see if any one has some pointers / give people an idea what this gun mite work like for some people. Rifle: WE-tech GBB SVD. Modifications: Over View - Spaced inner barrel W/. Teflon tape: to reduce barrel wip. - Modded gas piston spring to be stiffer: In order reduce impact on the bolt return to closed position - Converted 3X Green Gas Magazine's W/. CQB Russia HPA Taps HPA System: - 36cu/in. 3000psi SLP Tank. Modifications: Detailed - Spaced inner barrel W/. Teflon tape: while the mod is simple in it's self the process to remove the inner barrel is not, and i will say easier to disassemble to to put back together. all said and done i did 5 bands of spacer's made of Teflon that are 5 wraps thick Each. - Modded gas piston spring to be stiffer: In order reduce impact on the bolt return to closed position: i remove the Bias spring closest to the Receiver, than added Nylon Washer's to compress the spring at the gas block to stiffen the stroke - Converted 3X Green Gas Magazine's W/. CQB Russia HPA Taps (Note) "Due to the painting process From the Manufacture The Valley of the threads is filled in" which causes the threads to be an interference fit, so i would tighten the HPA Tap until the resistance was high, then completely back off the tap, fallowed by cleaning the threads, rinse and repeat until the O-ring could be fully seated. also the base plates needed to be drilled out to allow the Tap to pass though. No Field test as of yet Will Upload Photos later. **Edit** 9/14/2021 Planned Modifications: - Slide Rail Polish, Reason To Create a smother blow back Action to help control Recoil. - "Buffer Block" at the back of the receiver will have a rubber buffer installed to reduce recoil and help reduce internal wear. - Scope........ need i say more.