Five Easy Probes

[Adam77K]

Like a horseshoe in cross-section Paul?  Sounds like a good idea if it was rigid enough.
Though I'm not sure what the gains would be over a hollow probe with a large enough aperture at the bottom and nice smooth porting inside.

[Paul55]

That's was I was thinking    My thinking was that there would be more free space for the gas.

[sshewins]

My concern would be the flow if air, or turbulence. But the patent pending "no bolt bolt" sorta alleviates my concern with that. So I'd have to guess that it would probably be ok from that standpoint.

[johnf1966]

Very  good tests and thanks for taking the time to  produce all the data, very interesting.  I have an extended hollow probe in a gmac steel breech and am seriously considering taking it out.  The FPS is better as proven here but I find it can pinch  the skirt on the pellet and can also damage the head.  As the probe is pushing the pellet forward of the breech port the pellet head drops slightly into  the breechport and can  damage it. I use domed pellets, it does not work well with flatheads.  A damaged pellet will affect its aerodynamics on its way  to  the target.

[quickster47 †]

johnf1966 what you say is quite true. I find that when making and using an extended probe it is best to make it work with one particular pellet and try and stay with that pellet in that gun.  Which these days is easy to do.

Carl

[johnf1966]

Thanks Carl.

[Xxoo0o0o0ooxX]

Here are results from the fourth test.  These are the average of 240 pellets fired in batches of 30 pellets at a time using the Charles Mellon flow-through probe that I cleaned up ever so slightly to remove some tiny burrs.  Not that I am prejudice but this has always been my go-to probe for all my target guns.  Again the only thing done was a tiny drop of Pellgun oil to the o-ring and also a change of the powerlet after 30 shots.

The length of this probe is slightly shorter than the other two extended probes but I believe it has a more consistent seating of different pellet types if you are prone to changing pellets quite often. Although for this test I have used the same pellet type throughout my testing.  You can also see from the first picture that the opening is directly over the transfer port and lined up very well with the transfer port.

Carl

I love the flow-through probe for 2240's  Does anyone know if they are made for the P-rod pistol?

[quickster47 †]

I love the flow-through probe for 2240's  Does anyone know if they are made for the P-rod pistol?

Not sure if there are any being made for the P-rod but will look around.

Carl

[South Bay Dave]

Carl, thanks for the work you put into this and the cool data presentation.  Your findings were most helpful in my understanding of the head space past the valve.
I had only one thought that seemed untouched by the earlier discussions that I may try here at home if I can find the means.  I would make the wire probe as you did and then taper down the midsection of the probe between the tip and the o-ring and finish the tip in an enlarged round (skinny in the middle, wide at the ends and rounded on the face) -sort of a tear drop looking thing if you were holding the probe pointed down.   My thinking is that this would allow more of the air to collect behind the pellet and then be further increased in pressure as it moves past the widened tip of the probe thus compensating for the suspected turbulence issue - however, because this would be constricting on the air flow I don't know if there would make a positive difference.

Happy Plinking!


Dave

[WaltWhite]

Lots of great information here!  Does anyone know how applicable this information is for a 1377-type gun?

If I've extrapolated correctly from these seven pages, would it be best to stick with a stock bolt if you plan to run a variety of pellets?

[quickster47 †]

Lots of great information here!  Does anyone know how applicable this information is for a 1377-type gun?

If I've extrapolated correctly from these seven pages, would it be best to stick with a stock bolt if you plan to run a variety of pellets?

You can still use a custom probe with a variety of pellets and the loss of efficiency will most likely be very negligible.  So my suggestion is get yourself an extended probe and use it.

Carl

[sshewins]

Johnf, have you tried melting some wax on the breech screw? Ooze a little Crayola on the screw and form it a little. Should keep your pellets from hanging up and getting damaged. Plus, you can remove it later, if necessary.

[Poorman Plinker]

Granted that the test was about velocity and not accuracy and the tests were done very professionally and the results presented very scientifically. Thank you Carl. .

[arkmaker †]

Glad to see someone thinking about this again.


Another train of thought to ponder is when Carl and I talked about using a bolt that filled the bore of the barrel, pushing the pellet past the transfer port, which would only make contact with the back of the skirt, but then retracting while still leaving a seal on the ramp of the bore. This would leave the entire camber open, seal and do the least amount of damage to the pellet by limiting tilt that can accompany an extended bolt probe. Nothing really has been done on this because frankly it would be a PIA to make and the pay off just isn't there (for most folks).


Personally, I do favor extended bolt probes over hollows just because they are easier to make. That said, I would not trade the Hollow bolt that is on my 114 for anything. Even then, for the minimal gain that requires $ and/or time, the stock bolts can't be faulted to awful much. My 1740 uses a stock bolt and I have had great results and a fairly flat shot string.


Anyway, keep thinking and pretty soon you will be consumed with the 22xx/13xx platforms and on the verge of bankruptcy like the rest of us 
BTW: Welcome to the Forum!

[Poorman Plinker]

LOL Arkmaker... I may be new to this forum, but already way over my head in Crosman parts and spending way too much time on the topic. Thanks for the welcome and the thought provoking ideas.