What caliber bullet does the AR-15 fire and how many rounds per minute can it fire fully automatic?

The AR15 has a rate of fire of 650-750 rounds/min (M16A1) or 700-950 (M16A2/M16A4). Calibers: .17 Remington, .17-223, .17 HMR, .17 HM2, .204 Ruger, .20.MORE?

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