OK, now we're getting somewhere.
0.728 grams is about 12 grains. That's less than half the weight of even the lightest
.22 Long Rifle bullet, and though the caliber is smaller (.22 LR is 5.6 mm) the weight is still very light and the speed is nearly the same. And with them being spherical ... I just don't think you're getting what you want.
You're shooting the rounds very fast, but the effective range isn't going to be 200 meters. If this is meant to be armor-piercing, the effective range with the speed and weight you have now is 50 meters, tops.
But I don't believe the rounds can penetrate thick space-faring clothing, let alone armor.
The reason is that the bullets are too light, have a poor shape for penetration, and have a low
ballistic coefficient. It's as if you were shooting a
.17 HMR-like round, but without enough speed or weight to penetrate very far into naked tissue. Worse, the rounds lack the shape they'd need to pierce armor.
The coating of the rounds is duly noted, and that idea's sound. But at best, these BB-like rounds will penetrate an inch or so into naked tissue. If a person's wearing body armor, the rounds will bounce off without penetrating.
If other ammo is used, the calculations change. Needle rounds, for example, could be more effective against bare tissue, but even less effective against body armor.
Bottom line, however: Too light, too slow and of poor shape to do damage.
From the overall tone of the submission, the weapon is meant to:
- 1. Accept many forms of ammunition.
2. Extend the amount of time the user is in active combat (high ammo capacity).
3. Be relatively cheap.
4. Be durable and convenient.
5. Be effective in killing unarmored opponents.
I think to do this, the best change you could make would be to use spitzer- or conical-type projectiles as the standard round, and make them at least 31 grains (2g) in weight. No, you won't get much penetration, you won't defeat good body armor, and you'll significantly add to the weapon's loaded weight. But you will be able to pierce heavy clothing and naked tissue, and that's something.
(No offense meant by the links; I don't know who knows what I'm talking about or not, so I 'cited' my work.)