Why do some mechs only have IF instead of LRM specials?

[Thomas]

What is the reason for some mechs having IF only but other mechs having IF and LRM special rule?

For example - Catapult C1 has two LRM15s and also the LRM special rule. However, the Catapult C2 not only has two LRM15s, but it has superior LRM15s with artemis guidance yet it does NOT have the LRM special rule... only IF.

Why would two mechs, both with 2 LRM15s, not both have the LRM special rule?

[Alexander Knight]

Because the LRM special is used for alternate ammunition loads.  Artemis does not function with alternate ammunition, so Artemis equipped units do not gain LRM or SRM specials.

[Thomas]

Oh. Dang. That was fast reply. Is that really it? One mech has artemis and the other doesn't. Artemis doesn't use special ammo so it doesn't get the LRM special rule but there are no artemis rules in Alpha Strike. Seems an odd thing to be penalized in Alpha Strike for having an "upgrade". Doesn't seem quite right.

[Alexander Knight]

Not really penalized.  Artemis-equipped units have a higher damage value in conversion.

For example.  Twin LRM-20s vs Twin LRM-20s w/Artemis, all other things being equal:
Twin LRM-20 damage curve:  2/3/3, LRM 2/3/3, IF 3
Adding Artemis:  2/4/4, IF 4

[jshdncn]

That still doesn’t account for units like the Warrior H-7C. Standard LRM-10 but no LRM special.

[Starbuck]

That still doesn’t account for units like the Warrior H-7C. Standard LRM-10 but no LRM special.

see p. 126 AS Companion, converting special abilities.
you have to deal at least 1 or more points of damage at Medium range after heat-modification and before final damage value rounding for getting the lrm special. so one lrm10 is not enough.

[Tai Dai Cultist]

As an aside, the presence of the LRM special is a hindrance if you're not actually using alternate ammo.  Various defensive abilities can trigger if you shoot at someone and possess the LRM special.   Of course most of them also trigger by IF anyway (for example if the target has AMS), but IIRC not all such abilities trigger on IF.