The weighs you're giving (as far as I can understand ancient units of measurement) are for relatively light tactical suits, basically what is built in the X-Com uniform (after all it does have some armour value). Remember it's 1999, not 2014. The combat armour is something heavier, to be used against aliens... Oh you know, this is sci-fi.
(For future reference: The American M4 Carbine weighs 6.36 lb (2.88 kg) empty, 7.5 lb (3.4 kg) with 30 rounds. Meaning that the Xcom Rifle weighs roughly the same with a larger bullet size but decreased magazine size.)Okay, let me pull up the facts again.
Improved Outer Tactical Vest used by the American Military, (IOTV) medium size (complete with all components and pockets filled) weighs in at 13.9kg, or around 30 pounds. But this includes - but is not subjected to - 3 magazines for a rifle, a grenade, first aid bandages, food, broken down MREs, notebook, pens, maps, radio batteries, (for company mortar 60mm guns) a 60mm mortar round, a belt of 100rds of 7.62mm for the M240B machine guns, more ammo, 2 x 1qt canteens (can't always trust a Camelback), VS-17 marking panel, small squad handheld radio, flex cuffs, candy, a book to read, more ammo in mags, weapons cleaning kit, phrase book of the local language, compass, GPS and some other luxuries such as an ice pack or a candy bar. Reminder, this is ALL in the tactical vest. Now taking most of this stuff out, the armour weighs about half of what it is. Again, taking in consideration that the weight is spread across the torso and limited on the shoulders, it should weigh a little bit less than half of that. BUT most Xcom operatives will not take anything but an extra magazine or a grenade into the fight, meaning that the IOTV weighs even more less than 30 pounds.
(Source: A US Army Vet, 82nd Airborne edit: made it sound like I was the army vet. I'm not, by the way.)
BUT IOTV was in service in 2006. The OTV weighs 3.6 kilograms more than the IOTV, and the OTV was in service since the late 1990's. Meaning that most tactical vests the Xcom Project would purchase would weigh roughly around 8 kilograms, or 17-18 pounds.
Typical Kevlar Vests used by Military and Police forces around the world (different from tactical vests. No pockets and less armour plating) are around 6-8 pounds (3.5 kilograms), while civilian ones weigh 10-15 pounds (5-6 kilograms)
Now Dragon Skin armour, in it's current state, has no pockets and protects against a Fragmentation Grenade at point blank range and from most infantry firearms. It weighs in at approximately 5.5 lb (2.5 kg) with level 3 protection. This is the current iteration of Dragon Skin armour, and includes no pockets but has it's armour plating. I am not sure if there is a level higher than the Level 3 protection that it is currently at.
Here, we have a full body suit, the Interceptor Body Armour. IOTV and OTV are apart of Interceptor Body Armour, but do not use the full set of Interceptor Body Armour. This includes protection on the arms, legs, better coverage of the torso and groin protection. Other packages include a neck piece and even a combat diaper to protect super sensitive areas. The arm and leg areas are considered Level 2 combat armour since they do not protect from .44 Magnum rounds, but this is a case of pure penetration power and not Directed Energy Weapons which mostly rely on equal amounts of Heat and Kinetic energy. Plasma weapons are no exception. While they might provide limited protection against plasma pistols, taking a hit and protecting the soldier from most of the damage, they will not protect against anything else. These neck, arm, leg, and groin add-on make the armour weigh in at 33.1 pounds, or 15 kilograms.
Lastly, the last body armour I am going to cover, is the PASGT, or Personal Armour System for Ground Troops. Not based entirely in america, this is the most likely armour the Xcom Project would buy. Designed in the mid 1970's the PASGT refers to the helmet and vest together. In the US army the PASGT was simply referred to as Kevlar, or even Flak Vest. Other applications include night vision goggles and a riot control visor for the helmet. Speaking of which, provides limited protection against rifle ammunition, according to informal tests. The US army used PASGT in the vest format, which weighs in at 16.5 pounds or 7.4 kilograms. Overvest variants of PASGT nearly doubles this weight, at 25 pounds and 11.3 kilograms, but overvest was considered too bulky and most preferred to use one vest.
So what does all of this mean?
Remember how I said the rifle, when filled, weighs around 7.5 kilograms?
Well let's translate that. The Xcom Rifle weighs roughly around 9-11 strength points, when filled with ammunition. Considering weight distribution techniques and the LACK of equipment that Xcom Operatives/Agents/Soldiers receive, it roughly translates into anywhere from 3-7 strength points for armours. 7 for armour like Interceptor Body Armour, which is full coverage, and Overvest PASGT. In the middle are armours like Dragon Skin torso armour and OTV. Lastly we have basic Kevlar armour, which should weigh near to nothing, something like 2-4.
Again, all for the realism.
