What is the purpose of the odd gap towards the rear of the projectile?
Hard to say...
The probe is basically to provide stand-off, meaning it should have a certain length. The diameter and the geometry of the probe is there for structural and aerodynamic reasons. All of this is taken into consideration for precursors also, otherwise the precursor would lose a lot of their effect. You can see that if you look at cross-sectional diagrams that are widely available.
If you look at Russian and Soviet rockets with precursor charges mounted on nose probes they tend to bulge at the tip where the charge is mounted... the are not smooth aerodynamic probes like the one shown on this missile.
What scale are you using?
Scale is not relevant... look at the "launcher boxes" on the back of this turret (model):
And look at the missile shown. the length to diameter ratio of the missile and you can tell immediately it wont fit in such a short box.
the box next to the poster however only holds two missiles which are parallel forward mounted which would not be ideal for Drozd.
the boxes in the model image above are likely part of an APS system, while the larger tube launchers near the poster of the missile are likely ATGM tubes.
I have been thinking about it too. It is, of course, an annular gap, which complicates things a tiny bit. Irrespective of that, it should be the area where the rocket motor nozzles are. There may be many pairs of nozzles arranged circularly, with each pair possibly firing in tandem. This explanation, I think, is a good match to the outward appearance of the missile and also to the dynamics of solid rocket motor operation.
I rather doubt this is Dragonski... they would not adopt such a failed missile design now.
Personally I think it is a minor body extension to shift cg during flight... most ATGMs roll slowly in flight so two opposed rocket motors with their exhaust somewhere around that ring would suffice to provide propulsion for the missile to its target.
backpack ammo belt PKM looks awesome.
Even better would be PKP bullpup. The only thing missing would be a juggernaut suit hehehe.
It is an assault backpack and would probably hold up to about 450 rounds of ammo ready to fire.
Carrying that much ammo would restrict mobility, but having all the ammo on the gunner ready to fire means he is actually more mobile and better able to provide support in a fluid situation.
Normal operating procedure is for other soldiers in the unit to carry ammo boxes and when the unit stops the gunner sets up position and troops carrying ammo deliver it to him as needed.
If you have to move then that ammo has to be collected up because the gunner wont be able to carry it all.
With this backpack it means the gunner is ready to fire most of his ammo at all times.
There's actually a more refined self-feeding backpack made by TYR tactical for $4,000.
Unfortunately is says: RESTRICTED: US Government Sales Only
Hahahaha... yeah... no one else in the world can make a backpack able to hold ammo so by banning exports no one else in the world can have it.
I rather suspect the US system is not designed for rimmed PK rounds so it would probably be useless anyway.