I have been looking around the alliant powder site but i cannot find what the C.O.L. will be for a 300 Ultra mag. with a 180 gr. Sierra Matchking. I was wondering if anyone knows what it is. I am just reloading my first couple of cartriges today so any tips to reloading this case would also be nice.

You gotta find out yourself. The throats can vary quite a bit when you're loking at thousandths of an inch. One method (there are a few) is to seat a bullet in a case, smoke the bullet with candle fumes, then gently chamber it. Trial and error will show you when you've seated as far as you can without marking the bullet. That's your COL. For that bullet at least. To get a more meaningful number, go with a comparator, which will measure the length from base to ogive instead of base to bullet tip, which can vary a lot from bullet to bullet, especially with semi-spitzers with exposed lead points.

The Sierra Reloading manual indicates 3.575" for the 180 gr HPBT Match King