GTA
PCP - HPA - C02 Gate => QB-7X Gate -W/Co2 & HPA => : December 13, 2006, 08:49:07 AM
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I was reading a post on the Crosman forum about extending the bolt prob on a c02 gun. The reason they did this is to move the pellet beyond the transfer port in the barrel where the gas would have a good flow. I put a pellet in my QB78 and closed the bolt and then opened the bolt to see the location of the pellet in the barrel. It looked like the skirt of the pellet was setting right on top of the transfer port, I couldn't even see the port. My gun seems to function just fine with plenty of velocity, is the pellet suppose to sit right on top of the port ?
I have read about the mod you make to the bolt of the QB where you cut the prob off and drill the end and put a short rod to use as a prob. Will this mod move the pellet past the port in the barrel and maybe increase the velocity ?
Thanks Bill
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That's the idea anyways, remove another restriction for the gas behind the pellet. The pellet itself is the restriction in this case. Be a little careful here though, if you make your probe too long it gets hard to load a pellet:)
Dan
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In the .22 models the distance from the shoulder on the bolt to the end of the probe should be 1 3/8 inches, you can have the same lenght on the .177's also if you oval port the barrel.