What your opinion of a Leupold Mark 4, 2.5x8 mil-dot, and with a Bullet Drop Compensator (BDC)?

A gun shop here in town has one on clearance ($850).  The BDC is for the 62 grain bullet.  I mostly shoot 55 grainers.  How would you compensate for the difference in bullet weight?  Is this a big deal?

I've never used a BDC so I'm unfamiliar with their use.

I have a long distance shoot (up to 1000+ yards) coming up soon and do to a shoulder injury, I'll be using my .223 for it, and the mil-dot Leupold looks like it would be a good scope, but as I said, I don't have any knowledge using a BDC.

How would the BDC affect the use of different bullet weights from 50 to 77 grain bullets?

I love my Mark IV on my AR.  You say it has a mildot reticle so I assume the BDC is on the turret.  Leupold will make you a custom turret with a BDC for any bullet weight/velocity you like for about $80.  Out to 300 yards the difference is negligible but if you are shooting beyond that you will probably want a BDC for your particular bullet or switch to the standard turret that just reads in MOA.

You'll need to get a different set of target knobs to match the bullet weight / velocity you shoot to stay calibrated.  Leupold CS will set you up.  I have a M4 3x9 w/ 1/4 MOA knobs and it is kick-ass for stout.  Your 2.5x8 is even better in terms of eye relief.

I have one on my Arms Tech USR.  It is extremly clear and easy to use.  I actually use it for mixed ammo and find that my rifle is less than a half an inch off with M193 and M855 at 100 meters.  This scope has eye relief you can't believe.

It's a great combo.