Orks are the 40K army I have faffed about with most in the last few years and it\'s tough to make a really competative army at any size, but also really rewarding. 500 points is particularly tricky. I have used them in the last three Doubles Tournaments (with 400 and 500 point forces) and although it\'s slightly different because you have a team mate to back you up I think the same principles apply. I have no clue who you are going to play against most, so I\'ll try and make suggestions that are as versatile as possible.
The first thing that leaps out is the Stormboyz. The first problem is that with only 5 boyz your squad is incredibly easy to take out with shooting. Unless you can hide them completely during their approach even a small shooty squad in your opponents force will destroy them, or at the very least make them take a leadership test. If they break from that, which isn\'t unlikely, they can\'t mob up so they are gone anyway. Also, if they do get into combat they are unlikely to pass their mob size check, so will hit with initiative 2, and will most likely die before they get to attack.
A squad size of 10-12 is pretty much the way to go, but that is just too costly for 500 points, so I have to advise you leave them out of the plan altogether.
A big Slugga Boyz unit or two is definately good for a large force. At 500 points I think Slugga Boyz overkill will make your games rather boring by seriously limiting your tactics. If you are set on Slugga Boyz I\'d say one unit of 16 is the way to go. I have to disagree with OrkyDave about dropping the burna. They will almost certainly do more damage in one turn up close than a big shoota in a few phases of one hit and a possible wound on average. A nob with a power claw also packs a good punch if you are going to be against high armour opponents.
A Gretchin mob is my recommendation for your other Troop compulsory (although I would probably take a Burna Boyz unit instead of the Slugga Boyz, with the grots to shield them). Gretchin are fun, and mighty useful. Take a slaver and squighound and a good amount of grots and set them up in a packed line in front of the boyz. It\'s surprising how much unwanted fire they can soak up.
Your Warboss, who I guess will join a squad, is better off with two close combat weapons. If you can stretch to a claw as well as a chopper he has enough versatility to hit first and wipe out swathes of people using the choppa, or split from the unit to take out a tank, dread, monster or similar big bad using the claw.
The stripped down Warbikes are just awful in the game. They are vulnerable, have no choppas and will generally be ignored and do bugger all until they enter combat and get wiped out instantly! Buggies are must have in comparison. Two skorcha buggies (taken as two seperate fast choices) are cheap and terrifying to a great deal of units in almost every army. You will decimate squads with them or draw a whole lot of fire away from the boyz. Spikes and blades is a great upgrade for these against horde armies too.
Man I am going on aren\'t I? And completely tearing apart your list too. Sorry about this, if you have based it around the models you have just tell me to sod off!
OK I\'ll try and speed up.
If you do any of those things you\'ll probably have some points left over, so a few options.
Skarboyz with three burnas are nasty. 9 power weapon attacks on the charge with strength 4 hurts armoured troops a fair bit and three templates splats horde armies!
You don\'t really have much stuff to take out vehicles, so some Tankbustas or \'Ard Boyz with rokkit launchas could be a good idea, or get some heavy support from a kan or two (again as individual choices, not a unit) and arm them up with rokkits.
Remember that your mobs can fall back into each other, so even if one takes a kicking the elite models from it will drop into another, which will make it even nastier when it finally gets to krumping in and doing what Orks do best!
Use cover to your advantage if the enemy tries to assault you, and practice predicting distances big time! Getting the charge in against the right enemy units is so vital, and getting assaulted whilst out in the open is so devastating to your force that it\'s really important to be in the right place at the right time.
Hope that is useful to you. Sorry about rambling on.
