Forums › PCP Airguns › PCP Airgun – Discussion › Drill bit for transfer port Views : 1404 Likes : 0 Likes : 0 | Subscribe September 28, 2018 at 7:18 pm Link BluecupParticipant Member HI, I am going to open up the transfer port on my .25 Marauder to 3/16th" and was looking for some … Restricting the transfer port by it's size, on a regulated airgun yields lower power but no more shots. First the nominal weight of the pellet changes. In an Airgunner (May 1991) article, Hancock and Pope said that Venom didn't bother to open out the transfer port on Weihrauchs. On some of their other guns they have a valve spring setting which also … I would think that for the lightest 0.22 pellets that the best transfer port size … In the piston/transfer port rifles there's a massive blast of air going through that port. It would appear Tony has cracked the code for piston weight, stroke length, air chamber bore size and transfer port dimensions. I have 3 standard brass transfer ports so had a play with the 1 in the rifle after i had fitted a robert lane regulator which i had setup for 11.4ftlb! And combustion (and because it is compression ignition yes, it is Dieseling but not the destructive kind. The tranfer port is smaller the the port in the barrel. yep 1mm took it up 10ftlb so unless you are using a Regulator to adjust power be very carefull when opening up the brass transfer port. Do you think this has a negative impact on the efficiency of the gun? B.B., Caliber size would of course have two primary effects. Bore size transfer port and tune with the hammer, that's the way to go when you have no power restrictions. Airguns don't work the way you initialy think because they are realy fuel-air guns. The factory Weihrauch transfer port size seems to be fixed at 2.8mm, so a 4mm transfer port is twice the volume. In general a small transfer port flattens the power curve and moves it up in pressure range. Is it bad to have the area lower transfer port larger then port on the barrel. If you have a .22 calibre Beeman R1 humming along at 22 foot-pounds and you alter the size and shape of the transfer port, don’t count on the gun delivering the same power afterward. Gun I’m working on is a Marauder with a Cothran valve. “Alan”There is a limit, but there is a whole lot more to it than just the transfer port size.What is the rest of the gun like, and start with the valve and pressure. In that capacity, the tune of the gun relates directly to the length and shape of the transfer port. FX uses a valve opening limiter on Impacts which reduces power and increases efficiency. this is more a word of warning than anything else, i drilled mine out to 2.5mm put it on my chrono 22ftlb !!! With power restricted guns tp is just part of the tune, there are restrictions in all components and everything is made to work together. In terms of airgun efficiency, it could very well be the perfect formula… I opened my 77 port from 2.9mm to 3.9mm and using 8.4gr pellets the power went up by over 1fp and the shot cycle improved. performance of the gun. He suggests (and the gun is … )takes place in the transfer port. Yes, I said the shape, too. So I don't know how something in the line of flow would affect the consistency of the output to the pellet. Transfer Port Diameters - Ask Bob - The AirGun Guild The AirGun Guild. So the size and length of the transfer port is important. A friendly place to share one's interest in all things airguns. Would be a good idea to inlarge the lower area of the transfer port to match the port into the barrel.