https://www.youtube.com/watch?v=FXzn27vFb5Q

Does somebody know about the internal differences between this design and ultimax 100 Mk V?

There's enough differences that it's pretty likely that the only interchangeable part between the two is stanag magazines...

One of the biggest differences to the original ultimaxes (not sure about later marks) is that it's open bolt full closed bolt semi. It's also substantially smaller and lighter with a very different securement method for it's quick change barrels.

The mg X is in many ways a very highly evolved ultimax that has corrected most of the downsides of the original like the really long receiver length.

More or less, everything is different between the two.

What specifically do you want to know about?

I can try to find answers for you, but I kinda need more specifics to even start answering.

I really would like to know "how the magic happens". How it delays and distributes the recoil without the extra receiver space of the ultimax. I guess that recoil springs use all the space above the bolt carrier group, but I'm not sure

Thanks in advance!

I'll read the patent tomorrow and try to extract relevant sections Along with the relevant illustration figures... You can kinda see quite a bit of what's going on just from the illustrations of the patent. L. James Sullivan patents seem to be pretty universally beautifully and thoroughly illustrated.

Edit: if you do a Google search for the firearm blog Sullivan mg X patent and it has a link to the Google patent page.

the way i see it by looking through the patent images, it looks like something in the firing control group could have some plays in managing the recoil. So much stuff in there compared to a common simple open bolt sear used in most MGs.

My only concern would be how easy it is to detach the barrel. It looks not very rigid and could came off accidently. then again, i'm sure j. sullivan got everything figured out.

The barrel securement is actually really nice if you look at it, it appears to hold itself in dynamic tension.

And yeah there's some fcg and other magic that appears to sorta buffer in both directions so that they can keep the overall firing cycle energetic enough to make the gun run dirty and push through issues with sheer kinetic energy without making strong impacts happen at either end of the receiver.

At the end of the day It focuses a lot on dissipating excess energy not needed to power the gun cycling in several directions that are advantageous to the person operating the gun.

I'd kinda like to see what the gun does if clamped down a couple different ways and test fired. 

At the end of the day it's not secret what Sullivan is doing though, he's using a combination of destructive interference (like dead blow hammers) and spreading out the forces over a longer time curve instead of quick rise time sudden impacts

Agree. It looks hard and complicated to figure out what actually happened in the fcg during firing cycles. Hope someone could explain.

Also the piston head looks like it has some additional parts, like a spring and dual clamps thingy.

Nathaniel, do you know something about the details of last Sullivan's design iteration?

Not anymore than I've already published. The patent is pretty clear, I think.

Yeah, I decided not to try and redo what's already explained in the patent because I will inevitably get things wrong. And in the case of the patent in question which is illustrated beautifully and very completely documented in the claims, I think it's best to just let Sullivan (and his patent attorneys) speak for themselves.