i will be shooting a mathews q2xl 30inch draw at 70lbs. my arrows will be beman ics340's. i use a nap quicktune 3000 rest with no overdraw. i would like to order my arrows online precut. what length should i order?

Either 30" or 31"
Some people prefer an inch of clearence for safety reasons. I like to shoot the same length arrows as the draw length. That way I get a better speed.

With the 31 inch arrows, your bow will be shooting slightly slower because the arrow is slightly heavier and viseversa for 30"

Nic

You will want you arrows to be about 1/2" longer than where your arrow rest sets. I have a 29" draw, and shoot 29" arrows, my arrow rests set back about a inch behind my riser.

TAKE YOUR KIDS HUNTING AND YOU WON'T BE HUNTING FOR YOUR KIDS

You must remember that Mathews will be at least 1/2-3/4" longer than what the limb tag states.The Q2XL runs long,mine with a 27.5" cam draws 28 1/4".
To be safe I would order the arrows and the points seperate,then when they arrive mark where you want them cut,any shop should cut them for you then install the points.
There is nothing worse than having them too long or short.

I currently shoot a Q2 and I would recommend that you take an old arrow and make a ruler out of it with felt pen. Start from the pocket in the nock of the arrow. Have a friend with you and have him tell you the length of measurement at about 1/2 to 3/4 in in front of the arrowrest. This should be about the center of the riser to just a bit behind center. The riser was designed for this and has plenty of clearence for your broadheads. This should get you the most out of your Mathews. I have a 30 inch draw length and shoot aluminum with uni's. The arrows are just shy of 30 inches from nock pocket to end.
A note of caution with this set-up though. It is HIGHLY recommended that your rest have a tray or guard in the event the arrow falls off the rest at full draw and cuts the crap out of your hand.