So, I have been using a borrowed Aimpoint compM4 on my three gun rifle waiting to buy a scope and mount.  I got a smoking' deal on a Vortex scope and have it in hand...now here is the problem...I ordered a vortex mount for a great deal and it went on backorder the same day. I am scheduled to shoot the 3GN match in Birmingham in 3 weeks and I am weighing my options. So I am seeking y'all's opinions.

Do I....

1. Change to factory division and keep running the red dot?
2. Call the vendor that I ordered my mount from and see if I can cancel or change my order...but it still will not be here for a week?
3. Spend more money than I have buying a mount from another vendor and getting it shipped here quick, so I can practice using it before the match.
4. Run a mount I do NOT like, but can find locally. (Burris PEPR with top rails, the only 30mm mount I can find locally).

The match letter says expect the farthest shot to be 500yds.

Assuming you are talking about a 1 piece mount.  The Aero Precision mount is crazy light compared to everything else.  If it was me I would order one and cancel the Vortex mount you ordered.  I replaced all my mounts with them.

Well, impatience got the best of me and I followed your advice.  

I ordered another mount yesterday, and says it shipped yesterday. Hopefully I will have it early next week and that gives me 2 weeks to play with it.

I went with the Aero Ultralight extended, so we will see how it works.

Update: Ordered at 10am on Wed, will be delivered tomorrow. I should be shooting it this weekend!!! That is some damn quick service.

Shots out to 500, you're gonna want a scope. I know I would. 500 is doable with a red dot, or even iron sights. It's just a lot harder than it is with a scope.

So, in 3 days I received a new scope mount. Now if my range will become un-flooded, then I can sight it in before my next match.

Next one I get though will be the SPR aero or the 3" offset vortex. This extended is just a tad close for comfort. It'll work, but I think moving the scope forward and inch will make things a little better.