+1
I'd like to add:
The reason for the generally smaller rear sight aperature on the AR is that the sight radius is so much shorter than on the Garand (or M14 for that matter) that a smaller hole is necessary.
I believe that RRA gives you the option of .030" or .040" aperatures on its NM models. The .030" is, IMHO, only good for competition and then only if the shooter has young eyes. Take the .040" if you have a choice.
You should probably shoot with it a bunch before changing the aperature. See if you like it, 'cause the .040" on your RRA might work silmilar to what you're shooting with on your M1!
I think that RRA also gives you a choice of 1/4 or 1/2 minute clicks on the NM rear sight. Unless you're a really hard holder take this advice, from lots of experience shooting Service Rifle competition, get the 1/2 x 1/2 min option.
You can also hedge your bets with the rear aperture by installing one of the rtemovable aperature setups from B Jones, Albert Turner, and some vendors here on arfcom. They just screw in and out of the housing in half-a minute or less. Then you can easily experiment to get what you need. My B Jones setup came with five different size aperatures. Plus, you then have the option of installing a tiny corrective (colored if wanted) lens for serious target work. They go in same as shamayim described above.
HTH