I built 4 AR's using del-ton rifle kits. (anvil arms lowers) All have performed flawlessly in the years they have been running. One has more than 12,000 rounds through it. No significant issues.
Can't speak to the built out "sport model" but the firegroups, barrels and bolts all work fine as any.
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"You can have it fast, cheap and accurate...pick any two."~Me
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