I have a Gamo Whisper IGT and it is shooting at an average energy of 9.4 ft/lbs energy. It has been like this since new about a year ago. Will shimming the gas ram, as with a normal spring add extra power, or does the gas ram pressure remain constant even if shimmed. I have been told that the HW90 could be adjusted by a valve at the rear of the ram and a special pump. I haven't had the rifle apart yet, but wondered if anyone had fine tuned their gas ram. My goal would be 11 ft/lbs, so not much extra energy required, possibly 50 or 60 feet per second.
Edited by MarkHolding, 17 February 2017 - 02:49 PM.