I'm putting together a SPR build and I was considering buying one but I have hear mixed results with rifle length buffer tubes and rifle length gas systems. Anyone have any experience with these?

Thanks

I use one on my 10.5" carbine and my 20" rifle, with plans to add one to my 14.5" middy.

While I have a carbine extension on my 20" gun with perfect reliability, I don't see why a rifle extension would make any difference. The JP-SCS comes with a spacer to use with a rifle extension.

I use one in my sbr and my 20" grendel, they work great in both.

The JP capture spring really smoothed out the action on my rifles.  

Too bad I have to leave the state to visit them.  

I use the .308 SCS with a carbine setup. Very happy with it so far and would expect to see the same performance in a rifle setup. I'd suggest buying the spring pack for it, that will give you one lighter spring and two heavier spring's. The factory installed spring was too light for my build and I had to step up to the heaviest spring. 5 minute swap out. Just remember, once you've determined which spring is going to work best. Let the red loctite setup over night to cure properly.