Can you use the 300 Whisper ammo in a 300 ACC Blackout ? I know they are very close but not identical. Someone i know has a Blackout and having a hard time finding supersonic loads. Remington stopped the 123gr load and just has the 220gr subsonic. Thanks for the help

This thread on Quarterbore will answer your questions.
Quarterbore has a lot of 300 Whisper stuff in various threads and forums. This is a good site for the 300 Whisper.
My Dad shoots a 300 Whisper Contender pistol and rifle. We have quite a bit of fun with the fast twist rifle barrel.

300 BLK to 300/221 Compatibility Grid - What Dies & Components Work Interchangably - Quarterbore's Forums

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slim

Moving this to the wildcat section...perhaps you'll ge more answers.

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Chris in NH.

"some days, I wish my dogs could talk"

OK, thank you much
Thanks Slim

Most people say yes, they are close enough to be interchangeable. You can find a lot more information on AR15.com.
Personally, I like the .338 Spectre a lot better than any of the .30 caliber offering but it is even more pricey to shoot factory loads (SBR is the only maker of factory loaded ammo so far as I know) and is really a reloader's cartridge, made from modified 6.8 SPC or formed 10 mm MAGNUM brass, but it is a dandy if you are looking for something a little different.

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.300 AAC Blackout is not a wildcat cartridge. Remington is making ammunition for it. AAC is a Freedom group company.

.300 Whisper is also not a wildcat cartridge. Hornady is making ammunition for it.

They got their roots as wildcats, and as such, will probably generate more replies here.

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Chris in NH.

"some days, I wish my dogs could talk"