Platoon Weapons

[Fuchs]

Doesn't matter. It has been observed many times.

[JMA]

Doesn't matter. It has been observed many times.

You talk of exceptions. There are always exceptions. You want to provide your soldiers with the best terminal ballistic result at combat ranges. Don't get hung up on semantics.

[Compost]

Re-reading the NDIA 2012 notes on the LWMMG for the N-th time made two things very clear. One, the brief is slanted. It exaggerates the range gap by comparing the M240 on its bipod against the M2HB on a tripod (page 5), but tabulates weights for the M240 with tripod against the LWMMG with tripod (page 15).

See http://www.dtic.mil/ndia/2012armamen...662steimke.pdf

Two and more vitally, the reference to ".338in variant” (page 15) indicates the internal mechanism of the LWMMG can be modified and mated with an appropriate barrel to operate with some calibre(s) other than .338in.

One likely calibre is 7.62mm and especially a magnum cartridge, with 7.62x51mm NATO as a less likely contender. The .338in reference covers both the current 8.59mm NM cartridge and longer cased 8.59mm Lapua. An amateurish effort at mensuration suggests that the LWMMG feedslot might be able to admit something even larger such as a 9.3 or 9.5mm cartridge.

The power of such ammunition would seem too much for a lightweight gun. However it also seems that no-one inside/outside GD is prepared to fully describe what it is intended for and with the LWMMG.

[Compost]

My last post fell into a soundless abyss. So here is another attempt to obtain views on what GD Armament and Technical Products is really intending for the one or more ‘variants’ of its LWMMG.

The GDATP brief on the LWMMG at NDIA 2012 featured a somewhat misleading table that tallied weights for the 7.62x51mm M240B, 8.59x63.5mm LWMMG and 12.7x99mm M2HB as tripod-mounted weapon systems. The table ignored on-bipod weights and used different quantities of ammunition - 800 rds with the M240B, 500 rds for the LWMMG and M2HB – because those quantities approximate each gun’s cyclic rate of fire in rounds per minute. That supposed equivalence of 800 and 500 rounds is only sometimes appropriate. Also the tally did not include the weight of the containers/magazines holding each ammunition supply.

Ammunition for a section and platoon level M240B is typically carried in ILCE pouches as free belts of 100 or fewer rounds, or in 100-rd belt bags that can be attached to a bipod-mounted M240B to function as a magazine. The weight of a 100-rd belt (6.6lb) and magazine bag is about 7.1lb and one such bag can be carried in a large ILCE pouch. Alternatively - and especially when the M240B is mounted on a tripod at platoon or company level - ammunition is supplied in strongly constructed metal cans each containing two 100-rd belts of 7.62mm rounds in two cardboard cartons with cloth bandoliers. The metal can has a gross weight of 17lb and is suitable for use as an off-gun magazine.

The GDATP table lists the weight of a 50-rd belt of 8.59x63.5mm Norma Magnum ammunition as about 6lb. The brief also shows a 50-rd soft pouch/bag on the LWMMG. On a pro-rata basis relative to the 7.62mm magazine bag that 8.59mm magazine bag would weigh about 0.45lb empty and hence about 6.45lb gross. On a similar pro-rata basis, an off-gun ammunition can containing 100 rounds of 8.59mm NM ammunition would have a gross weight of about 15.45lb.

Ammunition for a tripod-mounted 12.7x99mm M2HB is usually supplied as a 105 or a 100-rd belt (29lb) in a metal can which has an empty weight of about 6lb. For completeness it is useful to expand the GD table to include the squad level 5.56x45mm M249 LMG. A 100-rd belt of 5.56mm ammunition weighs about 3.2lb and the M249 typically carries a 200-rd magazine bag that has a gross weight of about 6.9lb. As a short-range weapon the M249 is rarely mounted on a tripod.
 
The above data together with other ammunition and gun parameters (from the NDIA brief and various references) can be used to correct and expand the GDATP table to better inform consideration of the main bipod and tripod-mounted MGs that might be used by infantry units.

MG on Bipod or Tripod .. M249_B . . . . M240B_B . . . M240B_T . . . LWMMG_B . . LWMMG_T. . M2HB_T
Cartridge (mmXmm) . . . 5.56x45 . . . . 7.62x51 . . . . 7.62x51 . . . . 8.59x63.5 . . 8.59x63.5 . . 12.7x99
Projectile wt (gm) . . . . .4 . . . . . . . . .9.5 . . . . . . . .9.5 . . . . . . . 19.4 . . . . . . 19.4 . . . . . . 46
App Rate of fire (spm) . .800 . . . . . . . 800 . . . . . . . 800 . . . . . . .500 . . . . . . . 500 . . . . . . 525
Muzzle velocity (mps) . . 915 . . . . . . . 850 . . . . . . . 850 . . . . . . .810 . . . . . . . 810 . . . . . . 900
Effective range (m) . . . .500 . . . . . . . 800 . . . . . . . 1100 . . . . . . approx 800 . .1700 . . . . . 1800
Weapon length (in) . . . .42 . . . . . . . .48 . . . . . . . . 48 . . . . . . . . 49 folded . . .49 folded . . 65
Basic weight wt (lb) . . . 15.6 . . . . . . .28 . . . . . . . . 28 . . . . . . . . 25 . . . . . . . 25 . . . . . . . 84
ACOG sight wt (lb) . . . .. 2.5 . . . . . . . 2.5 . . . . . . . . 2.5 . . . . . . . 2.5 . . . . . . . 2.5 . . . . . . 2.5
Spare barrel wt (lb) . . .. 4.6 . . . . . . . 6.6 . . . . . . . . 6.6 . . . . . . . 6.2 . . . . . . . 6.2 . . . . . . 25
Tripod wt (lb) . . . . . . .. na . . . . . . . .na . . . . . . . . .11 . . . . . . . . na . . . . . . . 11 . . . . . . . 44
Ammunition (lb) [rds] . . 27.6 [800] . . 56.8 [800] . . . 68 [800] . . . .64.5 [500] . . 77.3 [500] . . 175 [500]
TOTAL GD+ (lb) [rds] . . 51 [800] . . . .94 [800] . . . . 116 [800] . . . 98 [500] . . . 122 [500] . . . 331 [500]
MG on Bipod or Tripod .. M249_B . . . . M240B_B . . . M240B_T . . . LWMMG_B . . LWMMG_T. . M2HB_T

The above table is focused on suppression and on the duration of fire as approximated by cyclic rate. However for any reasonable standard of accuracy, the lethality inflicted - as opposed to suppression imposed - by ball projectiles on a series of fully or partly exposed area targets increases with the number of rounds fired before those targets obtain cover. The next lines show the system weights of the M249, M240B and LWMMG when each has 800 rounds available.

MG on Bipod or Tripod .. M249_B . . . . M240B_B . . . M240B_T . . . LWMMG_B . . LWMMG_T
TOTAL w800 (lb) . . . . . 51 . . . . . . . . 94 . . . . . . . . 116 . . . . . . . 137 . . . . . . . 168

If NATO adopted 8.59mm NM ammunition and the LWMMG then they could be employed alongside current MGs that fire 5.56, 7.62 and 12.7mm ammunition. Alternatively, 8.59mm NM ammunition might wholly succeed/replace one or more of the current types of ammunition with the LWMMG similarly replacing the corresponding MG or MGs. Various options can be briefly assessed and ranked in a pseudo-math format where: + positive, - negative, +*n strong positive, -*n strong negative, . spacer.

Why pseudo-math ? Here’s an example.

Option 5: 8.59NM LWMMG as special-purpose MG for snipers
+ . light-weight barrel assists portability and is unsuitable for sustained fire
- .. sniper prefer rifles chambered for faster and flatter trajectory 8.59x71 Lapua Magnum
- .. 8.59x63.5 NM would be orphan round
= odds against.

- as opposed to the wordy -

Snipers usually have a choice of several long-range calibres and specialised types of rifle. Also snipers typically use match-grade ammunition that often employs a non-standard cartridge size. Perhaps snipers should be able to additionally select a MG that can fire that same ammunition. Such a MG should be light-weight and compact for ease of carriage and handling into, in and out of a location. However, such specialized MGs are not currently available. Mitigating against any prospective use of the LWMMG by snipers, the initial ‘variant’ (as described by GD) is chambered for the 8.59x63.5mm NM cartridge rather than the 8.59x71mm Lapua Magnum cartridge that has been widely adopted by snipers.

Several options can be briefly considered.

Option 1: 8.59x63.5mm and LWMMG to succeed 7.62x51mm and M240B
+ . 8.59NM & LWMMG harder hitting
+ . 8.59NM & LWMMG longer effective range
-*n. 8.59NM & LWMMG could not effectively replace infantry use of M240B because
. . . 100rd belt of 8.59 in magazine bag (& in ammo can) weighs same as 180rds of 7.62
. . . 8.59NM too powerful for parallel use in infantry rifle, also unsuitable for marksman rifle
. . . LWMMG_B awkwardly long compared to M240B_B
-*n. large expenditure invested in production facilities for 7.62 ammunition
-*n. ditto barrels, receivers and other sub-assemblies for M240B & other 7.62 MGs
= long odds against.

Option 2: 8.59NM and LWMMG to succeed 12.7x99mm and M2HB_T
+ . LWMMG_T is more compact and can be readily used on bipod
+ . also 2ndary use as compact MG on vehicle ring and skate, swing-arm mounts etc
- .. but inappropriate light-weight barrel
- .. 12.7 and M2HB harder hitting
- .. 12.7 and M2HB longer effective range
+*n. LWMMG_T system weighs less than 43% that of M2HB and occupies smaller logistic cube
-*n. large expenditure already invested in 12.7x99 ammo & M2HB & M3 & rotary
= odds against.

Option 3: 8.59NM LWMMG as successor for both M240B and M2HB
-*n as per Option 1, also Option 2
= long odds against.

Option 4: 8.59NM LWMMG alongside 5.56mm M249, 7.62mm M240B and 12.7mm M2HB
-*n . logistical load inherent in supply of four calibres of ammunition in general use
= odds against.

Option 5: 8.59NM LWMMG as special-purpose MG for snipers
+ . light-weight barrel assists portability and is unsuitable for sustained fire
- .. sniper prefer rifles chambered for faster and flatter trajectory 8.59x71 Lapua Magnum
- .. 8.59x63.5 NM would be orphan round
= odds against.

Option 6: 8.59NM LWMMG as MG for vehicles, and subsequently other purposes ?
+. .. 8.59 NM possibly superior to 8.59 Lapua Magnum for vehicle use
- . .. light-weight barrel unsuitable for sustained fire
-*n . logistical load inherent in supply of 3rd calibre of ammunition alongside 7.62 and 12.7
...... as per Option 4
= odds against.

Option 7: 8.59 LWMMG as trojan horse for 7.62 Magnum MG to succeed 7.62x51
+*n. prove soft recoil and ruggedness, then introduce a variant in 7.62 Magnum
. . .. 7.62 Magnum harder hitting and longer-ranged than 7.62x51
. . .. weight differential of 7.62 Magnum ammunition is less extreme than that of 8.59NM
-. 7.62 Magnum too powerful for standard infantry rifle, marginally suitable for marksman rifle
-*n .large expenditure invested in production facilities for 7.62x51 ammunition and barrels
+. some continued use of facilities to produce Magnum barrels etc
+. continue 8.59 variant as prospective MG for vehicles, see Option 6
- . light-weight barrel inappropriate for infantry use and especially vehicles
= marginal but best option so far considered.

None of these options provides a convincing case. It is unlikely that GDATP has gone totally off the rails so I have missed something(s). What is missing ?

[Compost]

Just remembered that Lapua Magnum caselength is 69.2mm sometimes referred to to as x70 mm, rather than 70.2mm which might be referred to as x71.