I just got an email from Midway USA:
Per your request for notification, we received the following:
SI Defense Barrel AR-15 300 AAC Blackout (7.62x35mm) 16" M4 Contour 1 in 8" Twist Matte
Supplies may be limited and are first come first serve. Don’t wait until they’re gone.
To view this item, click on the link in the next section.
Thanks for Your Business,
Larry Potterfield,
Founder and CEO of MidwayUSA
I got the following email from Redding:
We are shipping those to our dealers as they order them.
The part number is 80327 for a two dies set (full & seat) or 84327 for a three die set (full, neck & seat).
We have also made a Type S Bushing Neck, as a Custom Series die, for bolt action guns.
The two die set is recommended for semi-auto rifles and the three die set is best for bolt action rifles.
These dies are marked 300 BLK (300 AAC Blackout) but will work for the 300/221 Whisper if the seating die is readjusted for the crimp ring.
(Conversely, the 300/221 will work for the 300 Blackout if the seater is adjusted for crimp.)
If you call Graf & Sons, Midway, Midsouth, Natchez, Gunstop, etc. they can get the dies if they don't happen to have them on the shelf.
We can sell them directly, but it will be at full suggested list price and you must send a check as we do not take credit cards