As with most 3d printing it’s not so much that it is hard to do, just hard to get right!
Usually involves quote a bit of prototyping… where you measure and design, the print and trial fit… then repeat until happy.
Most would just run some holes to mount left and right pieces together with some bolts, I would go for more of a friction fit combined with some snap together lugs/cavities to keep it more seamless and natural looking. Not hard just long winded.
I guess by the time it would take it would be too expensive to commission someone to do it and too niche for it to be available online or off the shelf. Maybe I should look for a Men’s Shed with a 3D printer. I would have to act older than I am to get in though. Lol.
Or… keep floating ideas and give me some time, if a get a successful print for mine you’re welcome to have one 
Would also be dead easy to fill that void with a small piece of the right thickness styrene craft foam. 
plenty of replica modellers use it to great effect.
Easy enough to add holes and greeblies for detail, cuts with a stanley knife, easily painted and so cheap you can have twenty goes at it to get it right for the cost of a cafe latte.
It’s how I would do it if I was doing one for myself… because I know jack about 3D printing. 
Thank you for your kind offer @RokSolid. This guy has a good one but the infill would need a curved recess either side instead of being flat to look the business. I think he charges for the 3D print files though.
He’s on the right track.
Not sure if the styrofoam suggestion would hold up to a game @Friendly_Fire might work for prototypes though.
Fair enough. 
Just so you know, Styrene isn’t flimsy like styrofoam… much tougher. Closed cell, very dense like MDF but easier to cut and shape.
A lot of movie prop firearms are styrene builds for convenience.
You’ve got me thinking about filling the void in my LDT AUG now.
Cool, was not aware of that. Glad I could be a bad influence. Lol.
Yep. Often use closed cell styrofoam or styrene block to create the shape I need and then glue styrene sheet to the edges to get a neat finish. Closed cell styrofoam is often milled in CnC machines as the buck for a mould for carbon fibre parts
taking orders for that piece ? lol
I could certainly print one, would just ask for material cost/time and postage if you’re not nearby.
that would be awesome and no problem at all but wouldn’t be until after the new year, work slowing up for Xmas and working as casual. but yeah that’s no dramas, I’ll inbox you when I need it, cheers
I’m close but the from $99 is what turned me off.
Yeah you know it’s gonna be on only one and it’ll be that AK missing the stock and probably a gearbox.
GBU has the Thompson back in stock for $320 for the standard model with upgraded spring boasting 270fps
But… GBU ┐(‘～`;)┌
Same blaster is $255 from hobby though 
And a spring / oring gets it up to 340 fps, if its big numbers your chasing…(M110)
M100 would do 300…
a spring and oring aint THAT expensive…
Yeah, I would bet they just did the spring… or just inflated numbers and did nothing! “It is the gels you are using you aren’t growing them right… oh now 30 days is up sucked in, your problem now!”
Probably just sticking wells gearbox springs in, they’d have a stack of them from all their “custom competition range” 
