The topic is about the Army, but I think the discussion about calibers must be done looking at the entire Armed Forces. The main reason is that there is not a real optimization of calibers if it is done by branches. If some caliber must disappear must disappear in the entire Armed Forces.
I have been looking at the weapons present in the Russian Armed Forces, and I found present the following calibers (not included grenade, rockett or missilie calibers):
240 mm
203 mm
152 mm
130 mm
125 mm
122 mm
120 mm
100 mm
076 mm
073 mm
057 mm
045 mm (to confirm if continues in production)
030 mm
025 mm
023 mm
014.5 mm
012.7 mm
009 mm
007.62 mm
005.45 mm
I found all these calibers recently in production except the 45mm caliber.
Also it is possible to see how the less used calibers are the biggest, or are used by a good number of different warfare (like different warship projects), or by warfare with high number of units still present in the Russian Armed Forces.
Aditional calibers offered by Rosoboronexport today:
155 mm: Nato caliber.
082 mm: Mortar caliber. Decommission may be not totally finished.
018.5 mm:
005.66 mm: Underwater caliber. Decommissioned weapons liquidation. Ammunition in production at the begin of this decade.
005.56 mm: Nato caliber. Ammunition in production at the begin of this decade.
004.5 mm: Underwater caliber. Decommissioned weapons liquidation. Ammunition in production at the begin of this decade.
Other calibers used and/or produced until recently that are not offered today to export:
180 mm: Ammunition in production at the begin of this decade.
160 mm: Ammunition in production at the begin of this decade.
115 mm: Ammunition out of production at the begin of this decade.
107 mm: Ammunition in production at the begin of this decade.
085 mm: Ammunition in production at the begin of this decade.
037 mm: Ammunition in production at the begin of this decade.
011.43 mm: Foreign caliber. Ammunition in production at the begin of this decade.
005.6 mm: Ammunition out of production at the begin of this decade.
005.5 mm: Foreign caliber. Ammunition in production at the begin of this decade.
Conclussions:
1.- These 20 calibers of the first block are the result of a continuous process of selection done in the last decades. While 20 calibers remain, 12 are out of the Russian Armed Forces in recent years (without to count the NATO calibers).
2.- To see all these calibers still in production and to know that Russia has been directly involved in 5 wars in the last 25 years, likely means that the amounts of ammunition of these calibers in storage have not too much size.
3.- The range of calibers surviving is well balanced, without holes but with some redundant case still. There is not need of new calibers. The future changes can be for reduction.
4.- Assuming the total decommission of the 82mm caliber, the weakest caliber, and the first caliber to disappear, maybe the
73mm caliber used by the BMD-1 and the BMP-1.
5.- The rest of redundant calibers can remain easily until at least 2030.