Propellant charge TC-F (BMCS) 
Contents
Propellant charge TC-F — the upper module of the BMCS bi-modular charge system
The propellant charge TC-F (manufacturer's designation XF; English: Top Charge) is the upper module of the bi-modular charge system BMCS (Bi-Modular Charge System) for 155 mm guns.
It is a second-generation modular charge for separate-loading ammunition. According to its developers, it was created for long and maximum firing ranges.
The system consists of two types of modules. The lower module BC-E covers short ranges (zones 1 and 2). The upper module TC-F is used in zones 3–6: zone 3 — three modules, zone 4 — four, zone 5 — five, zone 6 — six. The modules differ in marking, colour, shape and the conspicuous black stripe on BC-E.
The bi-modular system is easier to handle than fabric bags, and the logistics of storage, transport and use in combat are simpler. For more on how it differs from the classic modular charge system, see the separate article.
The charge was developed primarily for 155 mm guns with a 52-caliber barrel and a 23 L chamber. Tests have shown that the system can also be used in guns with barrel lengths of 39, 45 and 47 calibers and chambers of 18–25 L. The system works in guns with 45- and 52-caliber barrels, while in old 39-caliber guns no more than 5 TC-F modules may be used.
The TC-F case is fully combustible and waterproof, silver-grey in colour. Inside is multi-perforated grained propellant (tri-base according to manufacturers' tables), an ignition set with a protective film (CBI and black powder), a flash suppressor and an anti-copper additive. The details of the design are shown in the diagram below.
Advantages of the bi-modular system:
- Versatility: complies with JBMoU (Joint Ballistic Memorandum of Understanding), suitable for all types of 155 mm projectiles.
- Operating temperature from −50 to +63 °C.
- Moderate barrel wear.
- Reduced muzzle flash.
- Automatic and manual loading are possible.
- Shelf life of more than 15 years in original undamaged packaging at an average temperature of +25 °C.
Structure of the TC-F charge
The diagram is schematic: the position and thickness of the elements are not to scale. Module dimensions are as given by the manufacturer.
Zones of the BMCS bi-modular system
| Zone | Composition | Muzzle velocity, m/s | Pressure (max.), MPa | Range (max.), km | Overlap | Charge weight, kg | Propellant, kg |
|---|---|---|---|---|---|---|---|
| 1 | 1 × BC-E | 315 | 60 | 8,0 | — | 1,9 | 1,5 |
| 2 | 2 × BC-E | 470 | 140 | 13,0 | min. 15 % | 3,8 | 3,0 |
| 3 | 3 × TC-F | 560 | 95 | 15,5 | min. 30 % | 8,4 | 6,9 |
| 4 | 4 × TC-F | 690 | 150 | 20 | min. 30 % | 11,2 | 9,2 |
| 5 | 5 × TC-F | 822 | 230 | 24,5 | min. 30 % | 14,0 | 11,5 |
| 6 | 6 × TC-F | 940 | 355 | over 30 | min. 30 % | 16,8 | 13,8 |
155 mm gun, 52-caliber barrel, 23 dm³ chamber, projectile equivalent to L15A1/A2. With a HE ER FB-BB projectile the maximum range is 43 km. The highlighted zone 3–6 rows are TC-F modules; zones 1–2 are made up of BC-E modules. The weight per zone is calculated by multiplying the module weight by the number of modules (BC-E — 1.9 kg, propellant 1.5 kg; TC-F — 2.8 kg, propellant 2.3 kg).
Test results for TC-F modules
According to an open article (Beránek, Lehký, 2012), the modules were first tested in a 100 mm TK V20 test gun (converted from 125 mm) and only then in 155 mm guns. The aim was to trace the pressure waves: they show whether the pressure near the projectile base exceeds the chamber pressure at the start of motion.
155 mm/45 cal. gun, OFd-Mk projectile (with a base cavity), 43.55 kg. The charge was heated before firing to 21, 50 and 62.5 °C. Below is the experimental module design (VAR4 in the article), not the manufacturer's production values:
| Charge | T, °C | V0, m/s | Pressure (piezo M1), MPa |
|---|---|---|---|
| 3 × TC-F | 21 | 547,3 | 101,8 |
| 3 × TC-F | 62 | 556,1 | 102,8 |
| 4 × TC-F | 21 | 680,1 | 167,6 |
| 5 × TC-F | 21 | 807,8 | 255,1 |
| 6 × TC-F | 21 | 935,4 | 380,8 |
| 6 × TC-F | 50 | 948,5 | 390,0 |
| 6 × TC-F | 62 | 958,2 | 405,0 |
Heating the charge from 21 to 62 °C raises the muzzle velocity with six modules by approximately 23 m/s (935.4 → 958.2) and the pressure by approximately 24 MPa. For 6 × TC-F at 62 °C the pressure difference between the chamber and the projectile base rose to 20.1 MPa (under other conditions — 2.7–4.6 MPa).
Test in the 100 mm TK V20 (14.4 kg projectile): 4 × TC-F gave V40 from 815.7 to 840.6 m/s and a pressure of 213–240 MPa.
Acceptance tests by charge weight were conducted with the full set of modules: 5 × TC-F in a 155 mm/39 cal. gun, 6 × TC-F in 155 mm/45 and 52 cal. guns. The measurement consisted of two groups of three rounds with two different charge weights, plus a group with three modules; 9 valid rounds in all.
Charges and conversion
Modular charge system
Modular Charge System (MCS) and Bi-Modular BMCS
Conversion of propellant charges
Conversion of MACS charges (M231 and M232)
Propellant charge conversion table
Propellant charges
Propellant charge BC-E (BMCS)
Modular charge M231 (MACS)
Propellant charge M232 (MACS)
Projectile L15A1
Technical specifications
- Manufacturer's designation: XF
- Purpose: upper module, zones 3–6
- Total module weight: 2.8 kg
- Propellant weight: 2,300 g (per MSM), 2,400 g (per Explosia)
- Diameter: 158 mm
- Length: 177 mm
- Propellant: tri-base, with additives
- Ignition: CBI + black powder
- Case: fully combustible, waterproof, silver-grey
- Modules per charge: up to 6
- Operating temperature: from −50 °C to +63 °C
- Shelf life: over 15 years (+25 °C)
Usage notes
The manufacturer forbids combining TC-F with other types of charges: do not assemble it with MACS modules M231 and M232.
Only TC-F modules (three to six) are used in zones 3–6, and BC-E modules in zones 1 and 2.
The manufacturer's data are given for a 155 mm gun with a 52-caliber barrel and a 23 dm³ chamber and a projectile equivalent to L15A1/A2 (HE ER FB-BT).
Zone 3 (three TC-F modules): muzzle velocity 560 m/s, maximum pressure 95 MPa, range up to 15.5 km.
Zone 4 (four modules): 690 m/s, 150 MPa, range up to 20 km.
Zone 5 (five modules): 822 m/s, 230 MPa, range up to 24.5 km.
Zone 6 (six modules): 940 m/s, 355 MPa, range over 30 km. With a HE ER FB-BB type projectile the range reaches 43 km.
Range overlap with the neighbouring zone — not less than 30 %.
Charge weight: zone 3 — 8.4 kg (propellant 6.9 kg), zone 4 — 11.2 kg (9.2 kg), zone 5 — 14.0 kg (11.5 kg), zone 6 — 16.8 kg (13.8 kg). If the Explosia value (2.4 kg of propellant per module) is taken, the propellant in zones 3–6 will be 7.2 / 9.6 / 12.0 / 14.4 kg.
Conversion of propellant charges
Modular charge system. Video
What is the difference between the Modular Charge System (MCS) and the Bi-Modular BMCS
Oleh Syrota (Georgich©) for the Armed Forces of Ukraine /
Share your experience of working with 155 mm ammunition.
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