Questions about CSS performance puck

[Terminator03 18]

I've had my S-12 dialed in for a long time now so that it's very reliable with all types of ammo, including cheap Wallyworld low-brass. I did a ton of internal mods including gas ports, fully profiled and polished bolt and carrier, JP stainless guide rod, Auto-plug, etc. etc. Well, recently I was placing an order to CSS anyway, so I decided to try out their performance puck just for the heck of it. I haven't had time for the range yet, but during the install, I noticed that the CSS version is quite a bit shorter than the stock puck. The stock measures .587", while the CSS version measures .527" high. The diameters are identical so that isn't a concern. Does the height matter? It seems like it would lower the compression ratio in the gas block similar to running lower compression pistons in an internal combustion engine. I would guess this could have an effect on my previously dialed in gun making the Auto-plug adjustments need to be re-done again since I had it dialed in for the stock plug. I am also trying the GS-01 brake in place of the Krebs flash hider I was running, which may also have an effect on the cycling, but not positive on that one. Any insight on this would be greatly appreciated. It will be a couple of weeks before I can test this at the range so I figured I could do some research in the meantime.

 

Also, just to verify since there were no instructions sent... the little nub on the new puck goes in toward the operating rod - correct?

[JonWienke 131]

Any time you change any component in the gas system (including muzzle devices, or altering barrel length), expect to readjust the gas regulator. You may get lucky and not need to readjust, but you should always test fire with a sample of all the different types of ammo you plan on using.

 

According to the factory, the nub faces forward so there is always a slight gap between the gas plug and the puck, so gas can get between them and push the puck rearward. But if you are using most aftermarket plugs, like the Tac-47 or the CSS 6-position manual plug, there is a recess machined into the rear face of the plug that is deeper than the nub on the puck, so the nub doesn't really do anything. If you turn the puck around when using one of these plugs, you'll increase your power stroke length by the length of the nub and increase cycling energy a few percent.

 

Just make sure that if you put the puck in "backwards" that it still has a little bit of play when the bolt carrier is all the way forward. The op rod won't be happy if the carrier stops forward travel when it hits the puck instead of the barrel trunnion. When you shake the gun front to rear, you should still be able to hear the puck clicking inside the gas block with the gas plug screwed all the way in and the bolt carrier all the way forward.

[Terminator03 18]

Any time you change any component in the gas system (including muzzle devices, or altering barrel length), expect to readjust the gas regulator. You may get lucky and not need to readjust, but you should always test fire with a sample of all the different types of ammo you plan on using.

 

According to the factory, the nub faces forward so there is always a slight gap between the gas plug and the puck, so gas can get between them and push the puck rearward. But if you are using most aftermarket plugs, like the Tac-47 or the CSS 6-position manual plug, there is a recess machined into the rear face of the plug that is deeper than the nub on the puck, so the nub doesn't really do anything. If you turn the puck around when using one of these plugs, you'll increase your power stroke length by the length of the nub and increase cycling energy a few percent.

 

Just make sure that if you put the puck in "backwards" that it still has a little bit of play when the bolt carrier is all the way forward. The op rod won't be happy if the carrier stops forward travel when it hits the puck instead of the barrel trunnion. When you shake the gun front to rear, you should still be able to hear the puck clicking inside the gas block with the gas plug screwed all the way in and the bolt carrier all the way forward.

Thanks, that makes a lot of sense.