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Iminanalog posted on r/liberalgunowners6w
If you're ok with added bulk, the impact pro from Howard Leight work great. 30db NRR. https://www.howardleightshootingsports.com/products/impact-sport-pro-electronic-earmuff Website has all the relevant data you asked for. https://www.amazon.com/Howard-Leight-Amplification-Electronic-R-01902/dp/B007BGSI5U