Ares G36 FPS Drops

I am currently trying to R-hop my Ares G36. Yesterday I had a working flat hop and today after fitting the R-hop patch my gun seems to shoot about 50fps (I have no chrono's) with maybe one in 15 shots going at what appears to be around the normal ~390fps. I have tested the gun with the hop turned down, the BB's drop right away, and with the hop up, the bb's can get a significant amount of lift. The Velocity appears to be consistently low no matter how the hop is adjusted. What could be causing my fps to drop so drastically?