I would also use loose powder because you can really dial in a load with it.

You didn't mention what type of scope you are replacing so I might be recommending something you are getting rid of.

The Burris Fullfield IIs, either in 2-7 or 3-9 are a real good deal right now (I prefer the 2-7 for a ML). Also the Vortex Diamondback line, also in 2-7, is well thought of. Pity they no longer make the Vortex Viper 2-7, that was a sweet deal.

Regarding whether to use loose powder or pellets, I would definitely go with loose, but ask or do a search in the ML section to get a full understanding as to the why.

Pellets are very simple to use, and usually 100 gr. in a 50 cal. behind a bullet in the 250 gr. weight range works fine. Downside to pellets ... I have found pellets less consistent than loose powder, but it might be worth a try. And pellets that I have found come in 50 gr. increments. Not a simple way to custom a load other than try different bullets. I use loose powder.

As for a scope? I am guessing you may be hunting both woods and ag fields???? I suspect that some of the ag fields might be expansive enough to test or exceed the reasonable far distance that your ML is capable of. Something like a 1.5-6x40mm or 2-7x40mm would be a good choice.