I tried this on my M1A and fired it 60 rounds. It dramaticall decreased recoil. I did not notice that noise was much louder. I did NOT notice a shift in impact or group size. Photo below shows all. I put my M1A back into its classic look and sold it. I am selling this muzzle brake, because I no longer have a use for it. $85 shipped Priority Mail. Checks, money orders, and PayPal are all good. I am a firefighter/paramedic and work 24/48...also, a family member is having surgery this coming week and will be out of town, here and there. Please email with any questions. I will return email ASAP when I get it.
Here is what Brownells says about it.
Link to Brownells page: Smith Enterprise M14/M1A Muzzle Brake
"Lets you spend more time practicing with your favorite high-power, match rifle without the recoil. Absolutely no gunsmithing required for amazing muzzle control and greatly reduced felt recoil even on select-fire rifles. Changes the sharp recoil that most shooters experience with the military stock into a soft push. Easily replaces the issue flash hider without alterations and includes the front sight dovetail and castle nut set screw. SPECS: Machined steel, manganese phosphate finish. 3" (7.6cm) long, .862" (21mm) diameter, 4.3 oz. (123 g.) wt."