I found a left-hand American Predator in 6.5CM. it should arrive next week. I've had the intended scope for a couple of months now, an Athlon Ares 4.5-27x50. The intent is to take it to Jason's class and learn how to run it properly.

My question is about scope mounts, bases and rings. The rifle comes with a factory rail over the receiver, but I don't believe it is Picatinny spec. Should I replace the rail, and should I go +20 MOA if I do? What about rings vs one-piece bases? I have a lot more experience with with AR type mounts, not so much with traditional two-piece rings. With a 50mm objective and traditional rings on the rail, what height rings will I need?

Clearly, this is a budget build, but I don't mind spending money in the right places,

Thanks.

Your scope has 80 moa of total travel. A zero MOA base would put you in the middle of that with 40 moa up and 40 down. With a 20 moa base, you will have 60 up and 20 moa down. That should be fine.

Find the rings you plan to buy and do the measurements on the rings with your scope to see if they will fit. Most 50mm objective will need medium to medium high rings.

I'd put a 20 MOA pic rail and rings on it. The scope is probably made for a 20 MOA rail to give you plenty of travel impact up. And the rings I use are either Badger Ordnance, Talley Tactical, or Nightforce Ultralite. All four screw, all with a hex nut that clamps the rings to the pic rail. Every rifle I own has a 20 MOA pic rail, including my .22 lr. I can move any scope to any rifle, and use it, with nothing more than a 1/2" wrench or socket. It makes scope and rings one unit, and makes the whole system modular.

I ordered an EGW 20 MOA rail. I'll wait for the other parts and measure for the rings. I'm not sure if the barrel will determine the height or the end of the rail. I guess the barrel as I can always modify the rail.

I ended up with Seekins .82" low rings and they have plenty of clearance. I guess I'm set.

Same here. Seekins with a nightforce 20MOA rail and no complaints here