LB-X ACs were always described as "BattleMech-scale shotguns", with the cluster munitions being consistently represented as
shotshell rounds (which fragment immediately upon leaving the weapon's barrel) rather than proximity-detonation "
Shrapnel shell" rounds (the latter of which most people tend to refer to as "flak rounds" and/or conflate with actual
canister shot rounds (which, as it happens, are closer to shotshells than Shrapnel shells, in that they typically fragment upon exiting the weapon's muzzle)).
The LB-Xs' dual ammo system mirrors that of (dual-feed/dual-tube) shotguns (to which the LB-X is consistently compared in the BattleTech source materials), as well as the ammunition systems used by real-world tanks (the LB 10-X would essentially be firing an advanced form of the
M1028 canister round used in the Abrams MBT (with something more like a bomblet or grenade than a tungsten ball as the submunition) as its cluster round, and an advanced form of the
M830 or
M830A1 as its standard/slug round).
Even TRO 2750 (in which the LB-X was introduced) uses the shotgun comparison (on pg. 08).
"In addition to firing the standard Dual-Purpose Armor-Defeating Rounds, the weapon may also fire a special Cluster Round that acts much like an anti-'Mech shotgun. After being fired, the round breaks up into several smaller submunitions."
Use of the phrase "after being fired" rather than something to the effect of "prior to impact" indicates that the fragmentation/break-up phase happens early in the firing cycle (e.g. "at muzzle exit").
The shotgun analogy is also used in the CBT Master Rules (pg. 132), as follows:
"The LB-X autocannon can fire cluster munitions, which act like an anti-BattleMech shotgun in combat. When fired, the ammunition fragments into several smaller submunitions. This improves the attacker’s chances of striking a critical location but disperses total damage by spreading hits over the target area rather than concentrating the damage on one location. Cluster munitions can be used only in LB-X autocannon, not in standard or Ultra autocannon types."
Note that the CBTMR description specifically says, "
When fired, the ammunition fragments into several smaller submunitions" - indicating that the shell fragments at muzzle exit, much like its real-world counterpart (the aforementioned M1028).
It also shows up again in
TechManual (pg. 207):
"An improvement on the common autocannon intended to expand the weapon’s role into anti-vehicle and anti-infantry work, the LB-X makes use of light, heat-dissipating alloys to reduce its weight and thermal buildup. These materials, coupled with a smooth-bore, multi-munition feed mechanism, make the LB more expensive than standard autocannons. However, the slight range increase and the ability to switch between standard-style bursts and explosive cluster munitions - both specially developed for this weapon system - more than mitigate this higher cost."
Traditionally, the LB-X family of autocannons are known for their ability to fire a standard high-explosive, armor-piercing (HEAP) shell as well as a shotshell-like cluster rounds (filled with a number of explosive submunitions equal to the number in the gun's designation) from the same gun - in addition to being lighter (essentially built from Endo Steel), cooler-running, longer-ranged, and very expensive.
However, the trade-off was that the LB-X was limited only to these two types of ammunition, while the Standard ACs had access to a wider variety of
special munitions, in addition to being cheaper to acquire and maintain.
By contrast, the oddly-named "flak round" (described on pg. 352 of
Tactical Operations) that is fired by Standard ACs - and
not the LB-X family - is what behaves as Bishop's proposal describes.
"Despite having been a proven technology in ages past, flak autocannon ammunition remains uncommon today. Intended to deal with airborne combatants such as VTOLs and fighters, this ammunition uses proximity charges to detonate in mid-air. While potent against fast-moving targets susceptible to foreign object damage (FOD), flak ammo is less effective against slower-moving targets on the ground because the charges scatter their shrapnel too far and too quickly to benefit from the target’s mobility."
Further compounding the issue is the flechette rounds, also available to Standard ACs and is directly compared to the LB-X cluster rounds.
From CBTMR, pg. 133:
"Flechette rounds are similar to LB-X cluster rounds, except they release a shower of metal slivers instead of shotgun-like flak. Designed to combat unarmored infantry, these rounds are ineffective against armored targets."
And from
TechManual, pg. 208:
"Developed by the FedSuns in 3055 for standard ACs, flechette munitions deliver a shotgun-like blast of metal shards rather than a stream of shells. Intended for use against infantry, flechette rounds can wipe out entire platoons of conventional troops in seconds and can even ravage battle-armored squads, but this ammo type loses effectiveness against armored targets such as vehicles and ‘Mechs."
(In other words, the BT flechette shell is a more direct descendant of the Abrams' M1028 canister shell.)
To reiterate (and summarize):
LB-X cluster rounds = canister-round/shotshell (fragments at muzzle exit) with explosive submunitions
Standard AC flechette rounds = canister-round/shotshell (fragments at muzzle exit) with non-explosive shrapnel
Standard AC flak rounds = proximity-detonated Shrapnel shell or HE shell with non-explosive shrapnel
The current "LB-X as shotgun" implementation, while in need of its ability to fire standard shells and a minor adjustment to its
choke setting, is demonstratably more "correct" in terms of BT canon than the Shrapnel shell concept being proposed, and should thus have that aspect remain unchanged.
3
