I'm designing three guns here: a two-handed rifle, a two-handed shotgun, and a one-handed handgun. All of them are breechloader guns, so they can only shoot once before reloading.
The goals I want to achieve with these gun designs are:
- The guns should have the biggest cartridge caliber that can be fired while standing.
- The guns should be able to shoot accurately. Well, at least it shouldn't be inferior to a musket in accuracy.
- The guns should have the maximum length of a battle rifle. For the handgun perhaps it should have a length similar to a desert eagle. Because the accuracy over long distances doesn't really matter here.
- The guns should be comfortable enough to be carried by a single soldier in "ready-to-fire" position.
- The guns shouldn't have a pistol grip.
- For the shotgun, it's preferable to have a few big pellets, rather than many small pellets.
The biggest cartridges I know are .950 JDJ and .50 BMG, but I doubt if these cartridges are able to be fired while standing. For the shotgun shells, I don't really know much about them.
So, what is the biggest cartridge for each gun that meets the above criteria?
EDIT: My world era is similar to early Cold War era.
EDIT2: Sorry if I'm not clear enough with my detail or if I can't clarify it further with better word, but basically to harm the enemy of my soldier, we need the most powerful guns to penetrate their armor. That's why, I gave a standard breechloader rifle for the frontline soldier. You know, it's like the more powerful version of assault rifle like AK47 or M16 with breechloading mechanism. For close quarter combat, I gave them the shotgun version. For personal defence, I gave them the handgun version. But all of them have to be powerful enough without hindering the soldier from shooting while standing.