'Recoil is the backward momentum of a gun when it is discharged. In technical terms, the recoil caused by the gun exactly balances the forward momentum of the projectile and exhaust gasses, according to Newton's third law.'
By definition, this -2 penalty is recoil. It's more than usual because there is more force than the gun is designed to handle. I get that. But it should in no way apply to the first round fired. Again, the additional force of the projectile and gasses exiting the barrel would have to push the gun out of position as the bullet is still in the barrel, and considering the high velocity of such a projectile, I find that hard to believe. Recoil works by adding a cumulative penalty because each shot moves the barrel slightly out of position. If the gun 'kicks to hard', then would not a shoulder pad and stock counter that? That would be recoil comp in action.
Now, as a GM I would look at this as a limiting/balance factor, not a realism one. I would not want people walking around with HP pistols or SMGs, so I would very much play up the Forbidden factor, and make them very, very hard to get. Expensive, too. Not something you want to toss away like those cheap and easy to get APDS rounds(which for my money, are more effective than HP rounds on a cost v return basis). HP rounds would be something the sniper would use. And because of that, I would not apply the -2 to the first shot, but to each addition one. I would pretty much end up doubling the recoil BEFORE comp is applied. -2 per additional shot each initiative pass. This is a take aim and geek that mother fragger kind of shot, not empty the magazine kind of shot.
This might be RAW v RAI debate, but I for one just do not see how the extra kick could possibly affect the first shot.
