I saw one very comprehensive list on this thread, but below is another. I just traveled to Colorado to hunt mule deer for my first time. I did a self guided hunt but bought a land owner tag. (didn't want to wait 7 years to draw). I worked with a local outfitter to gain an understanding of the terrian and what to expect. It was a great hunt.

I would definetly recommend getting a bi-pod or shooting sticks. My shot was 225 yards and I never woud have connected without the bi-pod. The grass was too tall for prone or kneeling, so standing was the only option.

Also, I'd recommend a decent range finder. I had a Bushnell scout I used for 6 years in the eastern woods. Never had shots more then 200 yards. In Colorado, my Bushnell Scout (400 on tree / 200 on deer) was just not enough. It couldn't read anything past 300 yards. After this trip, I bought a Leupold RXII with TBR. It great for up and down hill shooting.

The 270 will be great, I would practice for 300 yard shots in moderate wind.


CHECKLIST:
Following is a list of items we suggest you bring with you on your hunt. The gear you bring is dependent on the actual hunt itself and the time of year. A good rule is to have with you everything you think you might need to hunt for a full day alone, and in the case of an emergency you need to stay dry and safe for a night or two by yourself. You can survive for many days without food, but clean water and dry clothes are a must have on any wilderness hunt. Assume these items need to be with you even on a guided hunt.
BE PREPARED: (get in good physical shape, read the rules and regulations on hunting in Colorado, know the basics of backcountry survival and know some emergency first aid)
RIFLE AND AMMO OR ARCHERY EQUIPMENT
COLORADO HUNTING LICENSE AND NECESSARY HABITAT STAMPS
HUNTER SAFETY CARD
CAMERA/FILM
COAT/OUTER LAYER AND RAIN GEAR (light weight, packable Gore-Tex is good)
FLASHLIGHT AND HEADLAMP (with extra batteries)
HUNTING PANTS AND SHIRTS (at least 2 pants and 3-5 shirts, dress in layers, bring a belt too)
KNIFE, ROPE, GAME BAGS
BINOCULAR
EAR PLUGS (for snoring and shooting)
POLY-PRO LONG UNDERWEAR (tops and bottoms)
COMPASS
SOCKS (5-10 pair)
CAMP SHOES AND CLOTHES (comfortable and loose to relax in)
ROLAIDS OR TUMS(helps with altitude sickness)
HUNTING BOOTS (1 pair Gore-Tex)
GLOVES (one light weight pair and a heavy mitten)
HATS (ball cap style and wool cap, blaze orange)
COW ELK CALL
FLORESCENT ORANGE VEST & HAT -500 SQ.INCHES TOTAL. (hat must have orange on it, please read the DOW regulations before you hunt!)
GPS AND TOPO MAPS (recommended and helpful, bring extra batteries too)
EMERGENCY SURVIVAL KIT: (whistle, fire starter, small piece of foil, space blanket or survival bag, matches, Ibuprofen, mirror, rope, light weight plastic tarp)
PERSONAL HYGIENE GEAR INCLUDING A TOWEL
SLEEPING BAG (-20 degrees)
QUALITY DAY PACK (pack as light as possible each day!)
WATER BOTTLE/PURIFIER (we like the KATADYN EXSTREAM $39.99 from Cabela's)

HAVE FUN!: It is a privilege to be able to hunt in these wonderful mountains. Know the hunting regulations and respect the animals you hunt. Read the regulations on public land use (BLM and National Forest) and respect private property at all times. Help us keep clean, quiet camps and have a great time hunting in Colorado!