The 5.5 air springer barrels to .22lr is true, they are also used in Africa, you drill enough diamether for the case, replace the piston with a percutor thingy and you are basically good to go on models with thick barrels BUT.... still pretty dangerous, The .22 have to squeeze to that barrel more than with a legit firearm barrel, plus, I don't think a springer barrel got much of a heat treatment for tensile resistance. Those people are risquing their lives every time they pull the trigger, I bet that some of them got a pair of fingers or part of the cheek and an eye blowned off.
In that sense, a standard flobert black is much more safe, the flobert system don't actually uses powder, just fulminant, and the power figures range from 20 to 40 joule, not that far from a powerfull airgun, but still a lot of things could go wrong, air is air, and a detonation is a detonation with a much more dangerous pressure spike.
As of use a regular blank to shoot a marble, well... that would be easy, you just need to 3d print a external surrounding case or even make a aluminium or clay (?) cast for the blank to make it fit on that barrel, and here you go. Problems... I'm pretty sure that would be illegal in almost any country and state, plus, you can't put a rubber bump to give the ball some spin like in airsoft guns, but with that speed, I guess you are good at any regular handgun distance, smooth bore shotguns with round slugs performs pretty well at 80 metters or so.
THe question there is... why marbles instead of regular chrome or steel balls? sure I seen those marbles shatter rocks with literally not a scratch to the damn thing, but a firearm explosion sets a diferent stage for materials, for example, the mithical ice bullet of some cheesy movies is bullpoop, the firearm detonation pulverize the thing along the barrel, and maybe can shatter glass as well cause the sound waves of the detionation or some weird crap.
If you are on a state or a country where, making a DIY firearm that shoots marbles or round metal balls is legal, you can posibly walk to store and just purchase a damn military machinegun or something, so you don't have any need to do it, as for poops and giggles, well, Joerg Sprave have already prove that you can shoot a round ball with a blank with lethal outcome:
I have a "flobert" revolver, that is considered an airgun as well as a blank/starter pistol, by the gun legislation of my country (all legally bought). The thing with this revolver is, that it's actually much more versatile than an actual 5,6mm flobert gun, because it fires .22 caliber (up to 5.55mm) pellets with the use of short 6mm/.22 flobert blank cartridges (you know, those tiny, little acorn-shaped starter rounds). I've shot all kinds of pellets and slugs through that gun, mostly COAL Classic wadcutters, JSB Express 5.52s and Knock-Out (25.39gr) slugs. The slugs flew slowly, but sure hit hard, much harder than 15+ grain pellets; They were also quite accurate from this smooth-bore revolver and were being slung at some 140 m/s out of the muzzle. The energies the pellets/slugs developed at the muzzle of this gun, ranged from 15-22 Joules, depending on the brand of the blanks and the weight of the projectiles (the bosnian Pobjeda/Maxx-Tech blanks were the most powerful, second to the RWS/Geco brand and the S&B ranked the least powerful). Here's an article I wrote about this revolver on the site:
Greetings everyone, I'm about to discuss an "air" revolver, that most of you've probably never heard of and by the way, I'm not making this up, this thing actually exists and it's awesome as it can be, it's like a true S&W classic, but miniaturised in terms of its caliber, to shoot airgun...
www.airgunnation.com For certain now, this thing didn't exactly develop as much power, that a long flobert gun in 6mm would, with a rifled barrel. My revolver's got a 4.5" barrel. A full-power variant of a 6mm ME flobert long gun develops up to 50 Joules. This has been confirmed by the Czechs and Ukrainians, where guns like these are quite common and belong into the C-1 category in Czech Republic, where they're are a subject to declaration only, as of 2022. You do not need a firearms licence there to get a gun as such, just the delclaration is sufficient. In Hungary however, traumatic guns are sold over the counter - both 12mm and 15mm, possibly 9mm too. In France the authorities allow their citizens to transform (without any notifications required) blank guns, chambered in 9mm PAK mostly, into less-lethal, single-shot defense weapons by threading a Self-Gomm/SAPL rubber ball adapter into the muzzle of the barrel, which is of course, threaded. They call these kinds of weapons "Gomm Cogne" and they fire 15-20mm rubber projectiles and slugs that can penetrate a refrigerator door with more than 80 Joules at fifteen meters. Self-Gomm balls are 18mm, whilst SAPL are 20mm. These things are not toys at all and they're certainly adequate for home-defense in case of an invasion, with the use of rubber balls. Retay company even makes an 2"+ long adapter with a bore diameter of .68 - 17,3 mm, which means that you can even fire paintball cartridges out of a blank gun with it, although unsafely for paintball sports, because I think they'd have the potential to cause serious harm and trauma to whomever would be shot by one of these balls. The energy levels of rubber balls range from 35-50+ Joules with the SAPL adapter, which as I've already explained, would not exactly be lethal, however it could very well happen to be so.
And that brings me to the video you've shared... I've seen this video a while ago. For the last 20 years or so, both 8mm Knall and 9mm PAK front-firing blank guns were considered actual firearms and required a firearms licence for purchase in my country. Things have changed for the better since the last year, and they're now over-the-counter items, that anyone over 18 can buy and sell to another person of full age. Blank guns in 8 and 9mm PAK had to be top-firing only in order to be sold over the counter, whilst 6mm flobert - short guns were o-t-c all along. The reason this change in the law was made, lies in the fact that both PTB-certified guns and those that do not have a PTB certificate, but have a manufacturer that complies to the 2019 technical-parameters/specifications document, are made in such a way, that cannot be converted to live guns by ALMOST, if even possible, means. It kind of seems to me, that the governments within the EU have figured, that top-firing guns are able to be converted to live guns with a greater success rate than front-firing ones
UK still hasn't lifted their ban on front-firing guns and they're never going to, as things are getting worse in that country day by day for the natives, especially for those that are armed...
Back to the marbles... I've acquired the Sig P320 blank banger in 9mm PAK last year, as I've been running around with a 6mm flobert blank gun till then; I usually take a blank gun with me when I go hiking or mushroom picking, to scare off any possible wild beast I might encounter in my travels, we've got a lot of wild boars after all, and since I got that gun I've kind of been wanting to do some actual single-shot target practice with it, you know, by shooting marbles out with an adapter, as I've got plenty of marbles od all kinds. I even found an iron threaded tube in my local hardware store, that I could thread onto the gun, which has a 7mm inner diameter, and those marbles are anywhere in between 5-9mms, so it would work just as Joerg has described in his video
Now in order to shoot slingshot balls (of whatever diameter) with a blank gun, I'd require a threaded tube with the said diameter and there probably aren't any such out there, I know, cause I looked everywhere... but I have found this tube through which I could theoretically shoot marbles. Last year, by new years eve, I've probably shot more than a 100 firework cartridges with my P320, works just like the real thing, only it shoots rockets and fireworks
Love the damn thing. At one point, I headed out into the woods and shot a beer can with a rubber ball that I squeezed into the flare adapter, it crimped that can like it was nothing
I felt like I shot it with an actual 9 mil.
Yeah, I've heard about that glass bullet thing... it's bizzare that someone was actually to come up with such an idea, haha
One more thing about the flobert/rimfire type of cartridges I once heard in some podcast about the manufacturing of .22LR ammo; The fluminant as you've described it (I just call it the priming compound) is actually dropped in a liquid state into the empty cases during the priming process of reloading rimfire ammo, the cases are set up-right on a spinning table that gets powered up and which generates centrifugal force that then smears the priming compounds all along the bottom of the cases evenly, the more even the compound will get distributed into the canal of the trough in the rim, the more precise ignition will be and will therefore provide greater accuracy to the projectile. Now that's interesting.
