My Ulfsark, Huskarl, Húd, And Fárbjóđr armors are all infantry armor. Ulfsark armor is a simple armor made with ceramite (a durable ceramic material) and aluminum designed to slightly enhance the soldier's strength and endurance while providing basic protection against projectile and plasma weaponry. Huskarl, Húd, and Fárbjóđr armor suits have adamantium armor plating at varying thicknesses. Huskarl armor has a standard thickness that can protect from at least one hit from most weapons. Húd armor is less armor and more of a stealthsuit, so the armor plating is thinner. Fárbjóđr armor is the dreadnought of my armor suits. The Einherjar who wear these suits are like walking tanks. The reason why I don't like you penetrating any infantry armor in one shot is because you can protect your infantry with more than just steel and Kevlar. I understand my standard infantry and the Sækjar getting one shot killed, but my standard Drekrekkr and especially my Einherjar should be able to take some hits and keep going.
And with armored vehicles, solid projectiles are subject to basic physics no matter what they're made of. If you're firing an 88 mm APCR (Armor Piercing Composite Rigid) round, you only have about 250 mm of steel you can penetrate at 500 m distance with a chance to ricochet at slopes greater than 60 degrees, the chance being greater the more the armor is sloped. Angled armor also plays into bouncing the projectile as well as rounded armor. I'm not denying the fact that armored vehicles will have weak points. I'm just making sure you know they usually have very strong defenses.
I'm not talking about a special compartment. I'm talking about a whole new system to fire the solid projectiles. If you try firing the slug through the same barrel as the laser, you're going to destroy all the focusing lenses and make the laser part useless. It just doesn't work.
If it's more like aluminum, that's more understandable. But still, being malleable at high temperatures does present a significant weakness to plasma weaponry.
Yes, energy weapons are allowed. Somebody didn't bother looking at my factbook... 
I saw all of that and am eager to see what else you add.
I really, really don't want to have to fight you. Because that means that I would have to read your entire factbook and, in the immortal words of an ancient meme, "Ain't nobody got time for that". 
Fair enough. If you have armor that can block such weaponry from doing a one-shot kill and you have it in your factbook, that's fine by me.
Obviously, fighting armored vehicles is an entirely different ballgame than infantry combat. But my weapon, especially using a slug, should be able to disable external turrets and severely damage exposed mechanisms (i.e. joints, engines, turret barrels, etc) with ease. Piercing armor without multiple consecutive hits? Very unlikely.
The idea is that the laser would ablate the back end of the slug and vaporize it, sending it flying at supersonic speeds towards a target. The laser would push everything out the barrel, protecting the fragile focusing lenses and the power source from the debris. Think like a laser-powered grenade launcher.
I'm retconning the sensitivity to heat. Mistarillium (as I'm renaming it) will be lightweight, heat resistant, and strong but incredibly hard to work without advanced tools.
I didn't get that far, apparently. I knew plasma and laser weapons were allowed, but I didn't think that energy blades would be a thing. Energy-focusing crystal blade with a mistarillium core, coming right up.
I work a job, play hard in War Thunder, keep my place clean, and moderate and participate in several RPs. I still find the time to read massive factbooks. Why? Because I made the time! You can do it too. You're just choosing not to.
You really ought to read my factbook and see just how outclassed your forces are compared to mine.

Like I said, vehicles do have their weaknesses. But who would try to snipe the barrel sticking out of a turret? Not many people, that's who. Takes too much skill and a little bit of luck. In the immortal words of an ancient meme, "ain't nobody got time for that!" As for your projectile penetrating the armor, there are many factors to take into account. There's projectile mass, density, shape, and velocity coupled with armor thickness, density, composition, and shape along with other factors such as weather conditions and advanced armor systems, not even mentioning shielding. There are so many factors in play that most people can't comprehend. You're lucky you're talking to an engineer fully versed in weapons and armor technologies. Or unlucky depending on your point of view. What I'm saying is that landing a penetrating shot is not a likely occurrence unless you know where to aim the shot and can get it to land there. And as for what damage it does on the inside depends on type of ammunition and its effects as well as what the internal anatomy of the vehicle and which location it penetrated in.
Perhaps you should consider using a rail of magnets to induce linear propulsion, sending the projectile to hypersonic speeds. What I'm suggesting is a railgun. It's much more efficient and propels the projectile at a higher velocity. It's what I use. As for the laser protecting the focusing lenses, those lenses should be running all through the barrel. Unless you have a barrel extension, the projectile will destroy the lenses.
An interesting decision. I hope it works out for you.
A crystal blade? Crystals have unique structures which cause them to break right apart if struck at the right angle. Are you sure you want to do that?