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I am new to this forum and new to the 300 Whisper. I have been all over the web looking for info. Real simple:

1. What Subsonic Ammo/AR rifle combo works conisistanly together in .308?

2. Does an AR .308 lower receiver require modifications to use subsonic ammo? If yes, can other uppers be used with it?

Many Thanks!

Subsonic loads are very inconsistent, velocity wise, in .308. There is also a KB risk if the wrong powder is used. I think there is but one company that even makes subsonic .308 ammo. I tried it 8 years ago and there was still more noise that I wanted.

I doubt you can find or modify a semiauto to run with subsonics.

I use Accurate 5744 powder, mag primer and 200/220 Sierra bullets tightly crimped for very consistant subsonic loads in my 1:8 twist Encore in .308. They are plenty accurate. I wouldn't want to try to make them cycle in a semi auto action though.