22xx tube bleed hole and Disco valve

[sholo]

I was in a discussion on another forum about how the hammer creates an "air cushion" when it accelerates towards the valve, and different ways to remedy the problem (bleed hole drilled in tube, fluted hammers, etc...). Someone mentioned that 22xx tubes already had a bleed hole from the factory, so no need to worry about that. So, while I had my 2260 apart last night while I cut a notch in the hammer for the M-Rod trigger sear, I just happened to look at the bleed hole and noticed something interesting.

Now, most of you probably already knew this, and I'm just late getting to the party (as usual), but did you know that if you use a Disco valve in a 22xx tube, the factory bleed hole is useless? Well, I didn't! I knew about the bleed hole, but never even thought about the Disco valve being a little longer.



The end of depth gauge is where the end of Disco valve is. JUST long enough to cover the hole! And to think I've been using it like this for close to a year now. Needless to say, there is now a new, 3/16" dia hole right behind the factory one. Will find out tomorrow if it helps or not...

Todd

[rsterne]

The fit is not tight enough to completely block the air from escaping.... However, not wishing to take a chance, I grind a notch in the back of the Disco valve so that the air can vent out the bottom hole.... The 22XX and Disco hammers are also not a great fit in the tube, which allows air to leak out around them as well.... I think the problem first came to light in my Hayabusa where the hammer was too good a fit in the tube, the valve stem was a bit sloppy in the valve, and the combination caused HORRIFIC hammer bounce.... A hole drilled in the side of the tube just behind the valve cured it (thanks to Al)....

Bob

[sholo]

Just ran some shots over the chrony (with the new bleed hole), compared the numbers to what I was getting before, and lo and behold - gained an average of 10 fps no matter what PA setting or pellet I tried

This is even after lightening my hammer by 1 gram by cutting a notch in it so it would miss the M-Rod trigger sear.

Might be some merit to having the bleed hole even in a 22xx tube after all?

Todd

[rsterne]

Or, maybe you were experiencing some hammer drag even with the other trigger group?.... Two changes (or more) at once, you can't be sure....

Don't matter, though.... the final result is an improvement....

Bob

[sholo]

Or, maybe you were experiencing some hammer drag even with the other trigger group?.... Bob

Possibly, but I don't think so (?)

When it had the 22xx grip frame/trigger group, I had my spring guide/trigger overtravel stop set up so that when I squeezed the trigger, the sear stopped flush with the outside diameter of tube, plus, when I took it apart, I looked for (but didn't find any) scuff marks on the rear portion of hammer. I could see marks on the front section from cocking, but none on the rear.

This is all just pure speculation on my part, but like you said - doesn't matter, the final result was an improvement! At any rate, I'm done messing with it now, get back to shooting it rather than working on it...

Todd

[SeanMP]

I still think it's a good theory.

If the tolerance on the hammer fit inside the tube was a little tighter you could easily be fighting an air cushion

[SeanMP]

I'm done messing with it now, get back to shooting it rather than working on it...

I call Bull$h!t

[sholo]

I call Bull$h!t

Whatever do you mean?

OK, ya got me.... I still have to make a trigger guard, but HONESTLY - that's it! (and NO - I don't need any more ideas!)

Is it weird that I enjoy working on them as much (or more) as I like shooting them?...

Todd

[rsterne]

YUP!... if the 8 fps is repeatable and measurable, then you can assume you had an air cushion slowing the hammer.... I notch the back of my Disco valve to uncover the vent hole just for that reason.... I reckon it can't hurt....

Bob

[rsterne]

Todd, stay in the game and keep trying things.... If we think you are coming to conclusions not warranted by the methodology you use, we'll tell you, hopefully politely.... On the other hand, if you come up with something new we haven't thought of, I'll be the first to congratulate you.... and then steal the idea....

Bob