I can confirm that the strings for the Sniper Rifle are missing in the en-US language, but not the en-GB language. I checked the ruleset myself:
- type: en-US
strings:
...
STR_ROCKET_PACK: "Rocket Pack"
STR_ADVANCED_ROCKET_LAUNCHER: "Advanced Rocket Launcher"
STR_ADVANCED_ROCKET_LAUNCHER_UFOPEDIA: "Utilizing the Alien Optical Processor, the Advanced Rocket Launcher can be aimed faster than the original design and is able to fire guided missiles."
STR_EXPLOSIVE_AMMO_UFOPEDIA: "Explosive ammunition causes violent detonation on hit, which is destructive to both enemies and the environment."
STR_INCENDIARY_AMMO_UFOPEDIA: "Incendiary ammunition releases flammable agent on hit, causing immediate immolation of the target."
STR_INCENDIARY_AMMO: "Incendiary Ammo"
STR_EXPLOSIVE_AMMO: "Explosive Ammo"
STR_ADVANCED_FIREARMS: "Advanced Firearms"
STR_ADVANCED_FIREARMS_UFOPEDIA: "Working upon the most recent advances in human engineering, a number of weapon designs was developed to give the X-Com troops more firepower and flexibility on the battlefield."
STR_HEAVY_SNIPER_RIFLE: "Tactical Sniper Rifle"
STR_HEAVY_SNIPER_RIFLE_CLIP: "Tactical Sniper Rifle Clip"
STR_HEAVY_SNIPER_RIFLE_HE_CLIP: "Tactical Sniper Rifle HE Clip"
STR_HEAVY_SNIPER_RIFLE_AA_CLIP: "Tactical Sniper Rifle Alloy Clip"
STR_HEAVY_SNIPER_RIFLE_UFOPEDIA: "This heavy sniper rifle sacrifices mobility for accuracy and power."
STR_STORMTROOPER_ARMOR: "Stormtrooper Armor"
vs
- type: en-GB
strings:
...
STR_ROCKET_PACK: "Rocket Pack"
STR_ADVANCED_ROCKET_LAUNCHER: "Advanced Rocket Launcher"
STR_ADVANCED_ROCKET_LAUNCHER_UFOPEDIA: "Utilizing the Alien Optical Processor, the Advanced Rocket Launcher can be aimed faster than the original design and is able to fire guided missiles."
STR_EXPLOSIVE_AMMO_UFOPEDIA: "Explosive ammunition causes violent detonation on hit, which is destructive to both enemies and the environment."
STR_INCENDIARY_AMMO_UFOPEDIA: "Incendiary ammunition releases flammable agent on hit, causing immediate immolation of the target."
STR_INCENDIARY_AMMO: "Incendiary Ammo"
STR_EXPLOSIVE_AMMO: "Explosive Ammo"
STR_ADVANCED_FIREARMS: "Advanced Firearms"
STR_ADVANCED_FIREARMS_UFOPEDIA: "Working upon the most recent advances in human engineering, a number of weapon designs was developed to give the X-Com troops more firepower and flexibility on the battlefield."
STR_SNIPER_RIFLE: "Sniper Rifle"
STR_SNIPER_RIFLE_CLIP: "Sniper Rifle Clip"
STR_SNIPER_RIFLE_AA_CLIP: "Sniper Rifle Alloy Clip"
STR_SNIPER_RIFLE_UFOPEDIA: "This precision rifle is more powerful than a standard rifle and has excellent accuracy. However, it is harder to use and has a low rate of fire."
STR_HEAVY_SNIPER_RIFLE: "Tactical Sniper Rifle"
STR_HEAVY_SNIPER_RIFLE_CLIP: "Tactical Sniper Rifle Clip"
STR_HEAVY_SNIPER_RIFLE_HE_CLIP: "Tactical Sniper Rifle HE Clip"
STR_HEAVY_SNIPER_RIFLE_AA_CLIP: "Tactical Sniper Rifle Alloy Clip"
STR_HEAVY_SNIPER_RIFLE_UFOPEDIA: "This 12.7-mm caliber sniper rifle sacrifices mobility for accuracy and power."
STR_STORMTROOPER_ARMOR: "Stormtrooper Armour"
You can see the difference between the two codes above the Heavy Sniper Rifle entries.
I probably didn't have to prove it, but it's still good to save Solarius Scorch some time, right?
(Another quick note: while searching in Notepad++, I found that the Sniper AA Ammo string for the italian language (it-IT) is missing, too.)