I know this isn't an answer to your question, but I wonder about the SRO in this use case. Maybe the bigger 5moa dot would be not so bad, even though not the circle-dot you prefer.
Made in Michigan, top loading battery, lots of mounting options, and I think they are around $485 right now (without mount).
ETA: Jagerwerks BROS might be a cool accessory for a carbine.
I actually thought the SRO was only pistol-mountable like with optics plates, can it mount to a Picatinny?
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