1377 transfer port diameter

[MyCrosman]

How much should I drill out the transfer valve to get the most fps on my 1377? I guess that's what you call that little sleeve between the barrel and tube.Can it go to .395 mm's.Will it add fps or no? Everything else on the gun is stock.

[breakfastchef]

Where are you going with your pistol? Are you looking for fps, accuracy, both? The best bang for your buck is to install a flat top piston and flat top valve from a place like Mellonair or Mountain Air Custom Airguns. This setup easily will increase velocities at 10 pumps up to 100 additional fps. No, really! That is an easier mod to start off with while TP transfer should be lower down on the list. Also, adding a longer barrel increases velocity on the order of 5-10 fps per inch. That is sort of a general rule, but YMMV.

[Trophyhunter49]

breakfastchef is rite. I would do a Flat Top set-up 1st and a longer barrel . Think you will be happy with the results

[jSan22]

i think i read somewhere that .22 cal benefits better from enlarging the transfer port.

[1377x]

since you asked about opening up the transfer port i can tell you this
the stock transfer port should measure .140 inside diameter the most it can be opened up is to .161 best done if you have a lathe
there is another solution to the transfer port that is to use poly tubing for refrigerator/icemakers.it has an inside diameter of .170
here is a pictorial/tutorial of that mod
http://www.network54.com/Realm/CFTech/Bioportupdate.htm

heres some more readind for you
http://www.network54.com/Forum/275684/message/1230699502/Welcome+to+the+addiction.++Some+1377+information+for+you...
hope this helps on your your new found venture

[Motorhead]

Yup ... both the PC-77 ( 1377) and SP-250 are set up with @ .165" I.D. Truck air brake tubing.
Easy - peezy 

[1377x]

Yup ... both the PC-77 ( 1377) and SP-250 are set up with @ .165" I.D. Truck air brake tubing.
Easy - peezy 

is the truck airbrake tubing available at auto parts stores?

[Motorhead]

Napa or those stores dealing more industrial indeed should have it.  Typically in RED or BLACK

[JEBert]

Can it go to .395 mm's.

Double-check your sizes.  1377x's and motorhead's dimensions are in thousandths of an inch.  Your .395mm would be less than one millimeter which is much smaller than stock.  .395" would be larger than the pellet and probably larger than the outside diameter of the transfer port.
Cheers,

[1377x]

Double-check your sizes.  1377x's and motorhead's dimensions are in thousandths of an inch.  Your .395mm would be less than one millimeter which is much smaller than stock.  .395" would be larger than the pellet and probably larger than the outside diameter of the transfer port.
Cheers,