Recoil is effected by two things, and both of these things are also factors in the firepower of the weapon.
There's also some workarounds to make things less proportionate.

-Mass of the round particle
This is how heavy the bullet is, and naturally heavier bullets mean more kick.
-FireVelocity of the round
This is how fast the bullet shoots out, and faster bullets also cause higher recoil.
-!- AEmitter recoil altering technique
Shooting an emitter of lower mass/velocity, meaning low recoil, then the emitter can emit the actual projectile at it's full mass/velocity.
-!- TDExplosive recoil altering technique
Shooting a lower mass TDExplosive, meaning less recoil, which instantly gibs into the actual projectile.

Accuracy is effected by several things.

-ShakeRange
How much the actor using it shakes it whilst firing. The higher this is, the less accurate the weapon is.
-SharpShakeRange
Just like ShakeRange, but it applies to when your actor is actually aiming with the sights; when you see the three yellow dots.
-NoSupportFactor
The lower this is, the more accurately the actor can fire the weapon when the other hand isn't helping, because it's busy with another device or blown off or whatever.
-ParticleSpreadRange
This is the precision, the spread of the particles. For example, the Ronin sawed-off has a really high spread, while a sniper rifle would have a really low spread.

Firepower (even if you didn't ask) is effected by four things, in the case of MOPixels. You'll notice some of these also effect recoil.

-Mass of the round particle
This the the weight of the bullet, and naturally higher bullet mass means more punch.
-Sharpness of the round particle
This is how sharp a bullet is. It's simply how well it penetrates things; such as enemies or terrain. But it's only one of three factors in penetration.
-FireVelocity of the round
This is how fast the bullet goes when fired. Naturally, a bullet will penetrate more when it's shot at you than it would slingshot'd or thrown at you.

-ParticleCount of the round
This is how many particles the gun shoots; and more particles mean more inflicted wounds, should the particles all penetrate. The best example is a shotgun, and the shot they shoot, many smaller projectiles that aren't terribly impressive alone, but have a devastating cumulative effect.

I have this problem too. Basically, the guy can't reach far enough with his support hand to grab the handguard. You will have to move supportoffset back, sharpstanceoffset back, or both. Maybe you can increase Maxlength for the arms, but that could introduce a whole different set of problems.
Finally, you can try moving your BG arm offset as far forward as you can without making the actor look odd.

Lesson: Actors in CC weren't meant to use RL guns.

EDIT: I realized you aren't making actors, just guns. In that case all you can do is mess with the support and sharpstance offsets.