In the 1980s, the US Navy requested a new submachine gun to replace the MP5 then in use. In particular, the Navy wanted a gun that was optimized for use with a suppressor. H&K built two models of experimental guns in the 1980s to meet this request, creatively named the SMG and SMG II.
Both guns were hammer fired, closed bolt designs that used simple blowback actions. They had collapsing stocks similar to what would later be used on the MP7, and vertical front grips. The early pattern had a remarkably complex rear sight offering two different sets of range calibrations for subsonic and supersonic ammunition (out to 150m). The SMG II reverted to a more standard HK drum rear sight, but added a very interesting velocity-reduction system. A pressure vessel under the barrel was connected to the barrel via a set of holes just in front of the chamber, and when opened it would reduce chamber pressure and thus velocity. It could reportedly reduce muzzle velocity from 350 m/s (1150 fps) to 305 m/s (1000 fps), thus bringing it below the speed of sound.
The Navy tested both models, and decided that neither warranted replacement of the MP5. No other sales were made of the designs, but much of the developmental work would be put into the UMP program that came afterward.
It also would be a source of inspiration in the design of the 10mm SMG seen in the Fallout series.
Ian's video: [14:47]
https://youtu.be/e7hX2jWw8cU?si=
A channel you might not know about's take: [12:44]
Is there a source on the gun inspiring the design of the Fallout SMG? Because to me, the original Fallout sprite is a brick with a grip that shares little to no resemblance.
I know this page says it “resembles” an SMG 1 and 2, but it doesn’t claim the designer was inspired by the SMG 1 or 2, provide a source of a claim of inspiration, and is the opinion of some random Fallout wiki contributor. It is an opinion which I give no weight to after looking at both guns side by side.
I was going moreso off the nv model
Besides the similar lower, selector, and hooded front sight post, which are all also common with the mp5, it also has a long mlok-like hole in the handguard that resembles the two on the SMG 2. Which given the time period (before mlok began appearing on commercial guns) is a distinctive feature. There's also the the upper which has the same general rectangular silhouette (plus some greeblies).
Your image above is from a mod for Fallout 4, it is close but I’m going to stick to looking at NV designs.
Here is FNV concept art. The gun is inarguably inspired by an HK silhouette, but beyond that, specifically linking to the SMG 2 is tenuous. Everybody knows what an MP5 is, but suggesting that a very obscure prototype was the basis needs a pretty strong link specifically to features unique to the prototype.
The “MLOK” isn’t an MLOK, but the intended path of travel for the charging handle. If you look at the handle that hole is really the only place to go. There are reinforcements/guides around the hole, placed intentionally by the artist. There is a little metal nub in the hole that looks like it was made to be pushed by the handle, which looks like an intentional choice by the artist to show something inside that slot will get pushed.
The boxy front really looks like something from a Browning machinegun receiver translated onto an SMG. Whereas the SMG 2 is sleek and polymer, the NV SMG is ugly riveted metal. Which again suggests more visual inspiration from a Browning. The NV SMG even looks like it has a Browning-ish top cover and baby Browning charging handle.
Here is the ingame model.
I believe it fairly closely translates the concept art.
I think the link to an SMG 2 is too strained to definitively declare the NV SMG to be inspired by it, without something more to show a link.