The first strategem we've all used during at least 100 of our helldivers' lives:

The MG-43 medium machine gun!

I've pulled the files directly from the game and gave my absolute best fixing and adapting the model to be printed and as solid as I humanely could.

IF YOU PRINT IT FOR COSPLAY PURPOSES (hear me out cause it's important):

I have printed it out of PET-G HF and it turned out to be not only almost indestructible and as solid a piece could be, but also just above 2kgs at 105cm (roughly 41 inches) in length, giving it a nice feel holding it. That being said, I simply super-glued the internal reinforcement rods (aka ribs/ connectors) and put everything together into what feels like a single piece; no wobble or vibration whatsoever (at least on mine). I do NOT reccomend using PLA making it, go PET-G or tougher. 

I already took care of everything and put a lot of time and effort into this model, so just slice & print, then straight to the assembly. That simple.

Anyhow, let me give every disclosure I can that you seriously won't need for the sake of being proffesional if you reaaally wanna read it (but first, one short advertisement below):

Unlike the sword from my other makes, I didn't drop it on the ground full-force while swinging it around to involuntarily test its toughness, but I tried bending it with quite some strength and accidentally hit it against the wall and it's confirmed to be sturdy as heck. I also wrapped a sling on it to go on my back as I cosplay with the entire armor on and it handles some rough treatment like a king. The 5-wall profile has no trouble surviving pretty much whatever you throw at it as long as you don't drop on it with your entire body weight or use it as a crowbar of sorts.

I also pre-scaled the ribs to 98.5% to account for tolerance and gave them just enough room to slide in (bare-handed, without a hammer) with some super glue applied, so it's just a matter of pressing print and you're good to go! I know - I was also surprised that I really didn't have to struggle pushing them in.

If, for whatever reason, if your belts are loose, if your printer is 5 years old or whatever, you experience any issues just sliding them in with minimal resistance, simply scale them at 99%. Or just use a hammer and you may not even need glue anymore, but that's on you, not on me; I did my part leaving every possible instruction or caveat possible in this description.

There's also a control rod (or so I called it) aka the toughest and most important part regarding structural integrity. There is a pic in which I highlighted all the ribs in orange; should be pretty self-explanatory which is why I don't see the need of including an assembly guide or manual. Just keep track of the things you print, tetris them around a little before you glue everything shut and it's all good in the hood, brother in democracy.

DO NOT make any changes to the model; just slice as it is because I spent a long time making it work exactly the way it is.

Yes, the rods are MEANT to go exactly the way they go, even if they seem to only go in less than they should. I calculated the tension throughout the entire barrel (double-checked) and the way I made them hold everything together allows for the most stress tolerance in case of a hit while retaining maximum durability.

It does have some imperfections inside, but I guarantee and it won't affect the model, neither structurally, nor visually. You'll see what I mean when you press slice and you'll also see how trivial the thing I'm talking about is (just some minuscule areas inside that aren't fully filled but, if anything, they ironically ADD to the overall strength). I didn't bother anymore since that'd mean so many more hours of work for literally no change. I advise you not to bother either, because it's simply irrelevant and it's TOUGH AS (redacted) already!

I also included a version that is NOT meant for cosplay, but rather a decorative piece, which is ~20% faster to print, uses much less material and is definitely not as sturdy. That one is solely meant to be displayed on a shelf, hanged a wall etc and I cannot guarantee it'll survive any quicker handling or rougher roleplay action.