... hobby level printers ...
... commercial machine ...
Do you notice the distance between these two options...? It's like the difference between a hand operated pan brake and a 100 ton hydraulic press.
Don't grumble when you get a wheelbarrow and it doesn't perform like a dump truck.
I really don't see that much of a difference if you consider what people are paying for higher end hobby printers vs. the used prices on the commercial machines - It looks to me like you can get a "commercial" grade machine that may need some repair for under $5,000 USD easily.
Projectile weapons? That's a worry (to me, at least) - but, yes, you should expect a commercial machine to be far more capable - even if more expensive to acquire, operate and maintain.
It isn't a worry in the USA due to the number of weapons steadily climbing towards 1 billion already, as well as easy availability over the southern borders for stuff not normally sold in USA. For other countries with more tyrannical rules on self defense and weapons, I can understand how it would be a worry for the bureaucrats but it's really only a good thing for the freedom minded. Imagine this scenario: Someone is breaking into my house! Oh no! *prints weapon before murderer makes it through the door* (I know, this is a silly situation, but would make for a funny short film
What does "engineering grade" mean? Engineering is the art of achieving goals with available materials and processes. I make wrenches, structural joints and other parts using a hobby grade 3D printer. You just have to be aware of material limitations. And realize that one tool doesn't fit all applications and some applications are just out of reach for some tools.
There has been much hype about 3D printed projectile weapons, but the reality is not really more worrisome than the decades old zip gun made with pipes, piano wire and scrap.
To me it's material vs. dimensional stability and repeatability. It really doesn't look like you can print a lot of the more exotic materials without a heated chamber, or rather, you can't print them w/o a heated chamber if you care about the dimensional stability/repeatability. Also layer bonding for some of them. I'm not an expert in any way, I am learning about this and deciding if I want to get a commercial grade machine.
The 3D printed weapons aren't hype, these new glass and carbon filled exotic materials are pretty amazing, people just aren't talking about these efforts online much since it tends to trigger(lol!!!) the bureaucrats. I think we'll see some exciting developments in coming years, it may become very close to the new Lost In Space series (which I higly recommend watching!!!)
Danger, Will Robinson, danger!