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: Daniel DeMerchant posted recently one of the major causes of noise in the M98, the sudden release of blowback gas as the O-ring on the hammer reaches the side slot. I have thought about this and discussed it with an engineer friend and here are several of my 2 cents on the subject. : My first thought was to port the receiver just ahead of the slot, allowing the gas to escape over a wider area; problem is it makes lots of entry points for dirt. : My next thought was to cut grooves on the inside of the receiver so that the gas could escape past the O-ring and be vented into the rear area of the receiver. There could be lots of grooves just ahead of where the O-ring would reach the side slot, and some longer ones to allow a gradual release of pressure. You would just have to be careful not to cut too many grooves or there may not be enough pressure to cock the hammer, especially with C02 pressure changes in different weathers. : So what you need is an adjustable vent of blowback pressure, just like with the RT! How about mounting the valve from an RT and adjusting it to release most of the pressure, leaving just enough to cock the hammer. The outlet from the RT valve could vent more gradually, perhaps in a silencer arrangement with wadding filled chambers, to deaden this sound. : My engineer friend suggested a wadding filled cover for the side slot, a much simpler idea than mine, and doesn’t actually make any changes to the receiver, especially if you already have rear cocking. : What is really required is a variable blowback in the valve so that only the required gas is released, you’d get greater gas efficiency and less recoil too. This would require a redesigned CVX valve, a bit beyond my scope. : Any constructive comments ?