I'm in the middle of trying to figure out how to modify my JP SCS to work with my Revolution DI. I like the idea of being able to fiddle with not only buffer weight but spring tension. While the rifle runs fine, it chews the crap out of the brass (shaves off and raises up material off the base) and I've not been able to tune that out with the stock system. Does it with factory and hand loads. I've tried three bolts and two barrels, still does it even with a bolt that's been in use for a long time.
The Rogue/Revolution DI both use a buffer tube that's .5" longer than your standard mil-spec buffer tube, coming in at 7.75" for the POF. The spring is also longer and I don't think anyone makes a compatible springs in various rates both firmer and softer for tuning.
My JP was originally for a suppressed SBR so slightly heavier than normal buffer and I believe a slightly stronger spring vs. the standard offering. I then purchased the conversion parts for a 308 which consist of a much shorter back stop, new springs, a spacer, etc...If you drop the 308 configuration in the POF buffer tube, it comes up about .48" short of where it should interface with the back of the carrier. Using the supplied spacer, drilled out so the rod can travel through it, there's a touch of preload (compression) on the JP spring. Ok great, instructions say to remove some material until it sits flush where it would mate with the back of the carrier.
On top of that, if you fully compress the JP spring and then slide the carrier over the rod, the rod will impact the back of the firing pin. Not good and shaving down the spacer would shorten the distance between the rod and the firing pin.
Here's two photos of the JP SCS, spring removed with the weight at the bottom of the system like it's fully compressed, showing the overlap between the JP rod and firing pin. This is with the bolt rotated back so that's the furthest the back of the firing pin can extend theoretically.
We're looking at an overlap of slightly less than half an inch with the bolt rotated back and less with it moved forward, (.360"). By cutting down the spacer to remove any preload, the amount of overlap grows. Even if you went with a VLTOR A5 buffer tube which is .5" longer, you'd be cutting it pretty close assuming the JP mass bottoms out and the bolt moves all the way to the back.
Maybe the bolt doesn't move all the way back, I can't say. I'd think if you had a hot load and too much gas, it could happen pretty easily. The nylon spacer doesn't give me a lot of comfort as I'm sure it'll compress over time and could get chewed up as well.
Seems to me, for reliability, the entire system would need to be redesigned and the metal portion that would normally sit against the back of the carrier would need to be lengthened the appropriate amount, the rod slightly shortened and the weights adjusted to compensate for the increased mass of the extended metal face. At the very least, with the A5 carrier, you could use a 1.25" spacer at the front and it would work. I know aluminum will compress, maybe a titanium spacer? I have an extra tungsten and steel weight so I might be able to compensate.
