Probing uses an instrument that can and many times is inserted too far. This may result in an infection that can and does kill the snake.
The fact is popping never does this and is safer for this reason alone.
John Light's statement that popping has made a male unbreedable was the source of my statement regarding sterility. John, please re-read your own post. There is no way you could possibly know why the male you reference did not breed; yet you blame popping.
Popping is superior because one can visualize the hemipenes quite clearly, or not in the case of a female.
Males have been mis-probed as females because of bad insertion angles. Males determined correctly can still be damaged by over-insertion of the probe.
Females have been probed as males becuase the instrument was inserted too forcefully.
My daily job is working with hobbyists who need guidance with their snakes. I see mis-sexed animals all the time. We are in an era of herpetoculture in many cases which the breeder and the buyer cannot determine the gender of the snakes they are selling/buying.
I recently bought three 2500 gram females. The "breeder" had them for five years. Purchased as a trio (1.2) he tried and tried to breed them. To no avail. He was frustrated and sold me the animals cheap. This "male" was probed as a hatchling. It turned out to be three females. The probe job had to have punctured the female that luckily survuved the incident.
Popping errors make too many females. However, one cannot mistake a male.
Probing errors go both ways.
In skilled hands probing does work. We do it but only rarely.
It should not be attempted by beginners. Popping is far safer.
Yes this is an opinion. One based on the training of hundreds of hobbyists and over twenty years of keeping & breeding reptiles. I'll guess I personally have popped a few thousand ball pythons in the last five years. Only one, an albino male recently gave me trouble. His hemipene was less than a quarter of an inch despite his 1200 gram body weight and I could not pop him. He only probes five scales. Dan Sutherland was able to pop him successfuly (and safely) to prove the gender. Thanks Dan. You are a hero!
The animals we sell are properly sexed. Popping is our technique of choice.
Using the Barker's reptile years of experience, I have over five thousand reptile years of experience.
How many do you have? 
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