What your justification for denaying the smartgun and laser sight bonuses.
And what if im using a rifle with shortened barrel.

Firing from cover wouldn't apply most of the time, if I'm not mistaken when you fire from cover you're popping out from cover, shooting then popping back in. A sharpshooter would be hidden, not behind cover.

Extreme range is a -6 penalty now. So the total penalty is -16, -13 with the scope. 16 dice are needed (with scope), to be able to make the hit based on probability. You aren't going to kill the target with one shot though.

What, you mean a carbine? A rifle that's been shortened for the purpose of being used in closer range environments? Common sense takes over again.

Scope straight-up eliminates range modifiers. Unless i'm mistaken, scopes do not have ratings anymore. Penalty is -10. </nit-pick>

In a d20 system (vs. a success based system of d6s or any other die size) you can impose -1 per N meters of distance, where N is based on weapon type. Pistols get -1 every 5 meters, SMGs ever 10, sniper rifles ever 50+. You can also impose a minimum effective range, and impose penalties of -N per meter when attempting to fire inside that range.

Works pretty well in Alpha Omega, although as a whole the rules have a very fine line between "I can blow the crap out of it, hitting it 4 times a pass," "I can hit that once a pass" and "I can't hit that." Not to mention that if you build a character in one direction and find it's not working you're behind the curve (and will always be behind the curve) training up your new skill path. There's also this odd balance between "high stat, low skill" and "low stat, high skill" that isn't quite fair. It's perfectly balanced, but...oddly so (high stat: more random results, high skill: more bonus points--at extreme high skill levels you can use very few of your allotted 6 action dice per combat cycle and still succeed, high stat can allocate some dice and have a good average on those dice).

Let me know how your chemotherapy works out.

There is the minor detail that it's over 5 feet long and weights 35 lbs, but in SR that doesn't matter.

...I must be missing a reference to something here.

D20 causes cancer. Haven't you heard?

Oh, I see now. Got it. The game I actually mentioned--Alpha Omega--is only loosely based on d20. You don't actually get to roll many of them (well you can, for the critical success/failure, but you're rolling a d20 in addition to the other dice and it only matters if it rolls a 1 or a 20, so my group made it optional) unless your stats are over 72 (AO actually has a nicely balanced system that parallels D&D with the human average 10, human PC average 12 and scales up to 100).

I just called it a d20 game due to the type of rules set (dice values + mods vs. threshhold + mods as compared with [dice = stats + mods] vs. success threshold).