Chrono test: 1377 with and without extended probe

[kar120c]

My 1377 is detuned to <7,5 j so to be legal in my country so I must be very careful whit mods. One of this mods is the Gmac extended brass probe and steel breech.
I have made test with the extended probe and the results are almost the same as the stock probe:

with 7 grain pellet my pistol shots at 7,12j and 583 fps with stock probe and breech.
with extended probe the results 7,10 j and 583 fps.
Question. What is the longer probe, amnd when it could bring benefits?

[CraigH]

Extended probe results will vary with pellet.   If the pellet internal design/construction is open or deep, it may seat to the same location with respect to the transfer port as the fatter portion of the probe is pushing the pellet.   The whole idea is to seat the pellet past (forward) of the transfer port.

Given (or if) this is the case, that is why I like the flow-through probe design which pushes the pellet by the skirt vs from some point inside the pellet.