It was me who made the video. And I can explain both of the points made here. I'm not sure by scientific what you would mean outside of a chronograph reading of comparitive velocity. I clearly said these were self defense loads. By science do you mean that you are still wearing a mask because your covid shots haven't killed you yet?
On the velocity, most likely you have stuck to standard charges, which will generally not lead your barrel. But if you load a Remmy up to snot with 3f Triple Se7en, you will notice that there is lead stuck to the corners of your rifling, if not to the bottom of the groove also. Getting it out is a pain.
It is not the same with BP It is slower, so proportionally more powder burns outside the barrel. But I have to say, even with BP, it can and does tend to eventually become a problem with longer barrel guns, if you are loading them up. If you shoot a lot, over time, some lead will start to stick. On cartridge guns this is even worse, but with those you can always shoot a few jacketed bullets through to clean it out.
All steel is different, and even "pure lead" is different from one lot to the next. So I would not say that there is a specific velocity where you can expect it, but generally it is over supersonic. I don't know if the two are related. It could be that you have not looked closely if you are pushing your loads, and you just wondered why all of a sudden the gun shoots a pattern instead of a group.
On the loading rod, clearly you have not shot 10 stages of a SASS match with a 5 1/2" Marshall '51 navy. And yes, especially on Remmys the pin is very subject to break, and I have broken a few trying to get that last grain of powder to squish and be nice. I am very hard on guns.
My focus on the Black Powder Project is to bring some of these new shooters who have come in since '08 into our fold so that what we enjoy lives on into the future generations. The article accompanying the video generally explains things much better than I do in the video But this was not my best work lol. I retired from GA last year and this was my first contribution to the Digest in a while. Ring rust. I also haven't been around here much, because I buy too many darn guns. -ph