Bullet Matryoshka / Ammunition Nested Doll

1:1 Scale replicas of real ammunition nested together. I chose rounds used by various multi-barrelled firearms as far as possible. The rounds are:

5.56x45mm NATO as used by the XM-214 Microgun six-barrel rotary machine gun,
7.62x51mm NATO as used by the M-134 Minigun six-barrel rotary machine gun,
.408 Cheyenne Tactical as used in some sniper rifles (couldn't find a multi-barrel firearm round that would fit),
.50 BMG (12.7x99mm NATO) as used by the GAU-19 three-barrel heavy machine gun,
20x102mm as used by the M61 Vulcan six-barrel rotary autocannon,
25x137mm as used by the GAU-12 Equalizer five-barrel rotary autocannon,
30x173mm as used by the GAU-8 Avenger seven-barrel rotary autocannon from the famous A-10 Thunderbolt II which can fire 65 of these rounds per second!

Each round can either be printed in two parts (so you'd need a filament change if you wanted the projectile to be different), or in three parts - two for the case and a separate projectile which can be glued or just friction fit. Some rounds have two versions for the projectile: a looser fit and a tighter fit. This is only important if you want a good friction fit, if you're gluing then the regular one would be the better choice (the one without "tight" in the name).

Some of the rounds have pretty thin walls, make sure your slicer handles them correctly. For PrusaSlicer the setting is "Detect Thin Walls".
The models will look better if the seams are aligned. For PrusaSlicer set "Seam Position" to "Aligned".

Filaments used in the photos were Fillamentum Gold Happens and Polyalchemy Elixir Alpha Brass.