Springer air port

[bil601]

I know relieving the port on a springer on both ends will help air flow & if done with a tapper will form a venturi which will increase air vel., but has anyone made the port larger then relieved the ends. I would think this would get the air out of the piston chamber faster & increase pellet speed or at least shoot heaver pellets without as much loss in vel. I am speaking of stright through ports not angled thanks in advance.         Charlie Mellon

[bil601]

So Im geting nothing on this? No one has bored the port out before?

[Splash]

A bunch of us experimented with this idea, awhile back. You can go slightly larger, but too much and you'll loose fps, IIRC 5/32 is pushing the outer limits. A good polish would be the best and leave the size alone. You can do a search to find all of the info, from before.

[shadow]

That's right we did tinker around with port mod's and as Mike said there's a fine line there but we did sqeeze some extra power out of em. Ed

[RCnMo]

I haven't experimented with boring out the transfer port, but I plan on giving the compression side of my Quest port a polished taper just to see what it will do.

[bil601]

Thanks guys thats what I kinda figured.

[shadow]

Please keep us updated on your result's. Ed

[kiwi]

Hi.... Only a few weeks ago I bored out a 1.77 Stirling. The port was 3.2mm 1/8th ,I stuck a 4mm drill through it.
It had more power/fps but you could hear the piston slam its still going but I have only put about 15 pellets through it.
I reckin by about 100 pells the seal or spring will be stuffed The only chance for it now is 9+ gr pellets.
Ps ...I was told what would happen before I tryed it But I just had to fined out for myself.
O yes I do have a cheap Stirling air rifle  for sale!!!!

[bil601]

I think I was on the right track with the venturi. I believe what is needed is high pressure air on the piston side & high vel. air on the pellet side. I am making some hard wood tapers & using diamond lapping compound. Going to be slow going but its simple & it works. You can tell what shape you are getting by the marks on the wood & the wood holds the compound nice. The gun I am working on is a QB25 you dont hear much about these.

RCnMo - 9/5/2008  8:21 PM

I haven't experimented with boring out the transfer port, but I plan on giving the compression side of my Quest port a polished taper just to see what it will do.

how are you gonna get in there?

[bil601]

Im going to make a wooden guide block that fits in the piston chamber then slide the hard wood dowel through the hole & use a hand drill to turn it. That side needs a short sharp taper the front gets a long shallow taper. This should form a high vel. venturi. I think I am going to use a B2 as  a test bed. Ill drill out the to 3/8 & make drop in ports different shapes & sizes or maybe thread & screw them in. I can always bring it back to the stock hole/ Its raining here so its something to do.