1377 valve question

[Colt25]

I'd like to turn my 1377 into a .25 or larger carbine, just for novelty. But I'm wondering if the valve is large enough. I don't care how many pumps I need, so I can bore it out cut threads off etc.
Just for a fun gun, for plinking so slow velocity is okay but I want it to still get out of the barrel with some oomph.

Thanks

[targettgii]

I would think so Mountainair builds a .25 pumper I think Noah had one.

[Colt25]

I would think so Mountainair builds a .25 pumper I think Noah had one.

Hmm.......*gears turning*....

Is there a list of mods for 1377 valves? I know of porting, valve stem slimming, flat topping, and a few other common ones.

[targettgii]

That is about all I can think of too.But I buy parts.

[bgmcgee]

I think you might be able to hog out the inside for a little extra volume. You can also take a couple of threads off the cap of the valve for another increase.  Also look at Wyoman's stickies about pinning the check valve. That adds a little more too.

[K.O.]

An alternative to pinning the check poppet is to sleeve the intake passage with brass tubing,   you can reduce the size of both poppets.  If you have the right tools you can use a 664 pump tube (I used a 2100b but that is a whole nother story) also if the right tools can move the exhaust seat back a bit.