In all defense to Xplorer, their kit looks like an excellent one, my Version of the Xplorer Xpower one day will have this powerplant in it as the current R-Spec and i'm sure with stephans it will beat the R-Spec Retaliator I have now, probably 150+ feet flat.
Next I tried a new idea, since this is the gun that always gets it first, I broke outs some gunsmithing tools and countersunk a Retaliator dart bolt so that the load finger no longer drags on the dart on the way out, Shown Here on an aluminum bolt sled assembily
The result was wonderful, I did need to buffer the piston with a piece of felt and glue it i n there because it wasn't latching correctly at first, and I also filed some rough points off the piston (seam marks) and put in several layers of teflon tape. Worth the work however, this stuff is tough ass composite, most likely a strong thermoset casting resin like epoxy. Still working out some kinks, but it fires great. Here Are some other pics.
In foam we trust, I'll see you in Disneyland.