...if you can call 50fps a big difference...
The difference in the velocity is 2x, which is a fairly significant difference. But that's not really the main point. The main point is that 4X
FEWER rounds resulted in 2X
HIGHER velocity due to increased pressure.
The test was attempting to find some basic method of insuring that safety was maintained and ended up proving that what was perfectly safe in one gun resulted in a 100% velocity increase due to pressure with 75% fewer rounds shot. How do you make a general rule based on those results? The answer is that you can't.
It's not hard to shoot several hundred cast rounds through a Glock with NO leading at all.
He does indicate that he has "seen some Glocks that do not seem to lead"--but then points out that the tests he's carried out show that the same load in another Glock will result in leading. Again, the point is that it's not possible to say that if you follow this rule, if you do this, if you don't do that you'll be safe.
Furthermore, your assessment that the apparent lack of visual leading means that there is no pressure buildup is mistaken. The pressure measurements he did (and details in the book) indicate that there is even a slight pressure increase from shooting a number of jacketed rounds due to the small amount of fouling buildup caused. A little thought will reveal that if even the small amount of fouling/metal fouling from a jacketed load results in measureable pressure increase, it should be plain that even when leading doesn't seem to be obvious or significant there can still be pressure buildup as a result.
In addition, the testing shows that while the pressure increase from jacketed loads rises only slightly and then levels off, the pressure increase from leading doesn't always level off until well after the pressure is high enough to blow the gun and the increase isn't linear. That means that while the pressure increase from one round to the next may be small/incremental at first, as the progression continues, the pressure increase from one round to the next will increase until it is increasing dramatically from one round to the next.
And yet, he did.... His crappy load...
If you really have an interest in learning about this topic, you should read the book. Even if you don't have an interest in learning about the topic, but still want to speak intelligently about the contents of the book you should read it.
Basically nearly everything you've assumed about the book is incorrect. The testing done took place over a long period involving many different loads, different bullet hardnesses, many different guns and many different testing protocols. Some of the testing was actually done for clients to determine if there was product liability as a result of an incident experienced by a client.
I obviously can't and won't reproduce the entire chapter here, but your repeated insistence that this issue boils down to one particular loading that you claim is "crappy" is a massive oversimplification and a terrible misrepresentation of the material.
You have to understand it's difficult for me.
I think you may believe that I'm trying to change your mind. I'm not, that's why I've said twice now that the chapter is a good read "
for those who haven't already made up their mind".
If you choose to ignore the testing results and information, that's purely your business, provided you don't do it next to me at the range. It's your gun, your fingers and eyes, your choice. I'm not trying to change your mind because, frankly, I don't really think it's possible given your responses.
So why did I even chime in? Because not everyone who reads this thread will have made up their mind to the point of being resistant to the facts. I think it's important to let people know that, contrary to what is often claimed on the internet, there is
hard evidence that shooting lead (unjacketed/unplated) bullets in factory Glock barrels can be dangerous.