Go to
www.quarterbore.com and of course ar15.com for more complete discussions on the .300 Whisper (.300/.221 Fireball).
As far as components go, as long as you have access to .223 brass you'll never have to worry about brass as you can make it from this case. Using .221 Fireball brass (when available) is ok too. Rumor has it that Starline is going to manufacture .300 Whisper brass for the public. If that's so, it'll do nothing but boost interest in this neat little cartridge.
Of course, bullets and fast shotgun type powders will always be available. Using hard cast bullets may be an option here if you are very careful.
The only dies you should consider purchasing are Redding - period. They are by all accounts far and above the best dies in this cartridge and include a 7mm expander ball assembly to help neck up brass. Dies are likely a stateside only option.
The use of an adjustable gas tube is highly recommended and will allow you to use a wider variety of load combinations that will cycle the firearm. The Fulton Armory tube is highly regarded.
By the way, you never mentioned the twist rate on the Oly barrel. Is it 1:10 or 1:8? For heavy (+180-200gr.) bullets the faster twist may be necessary when loading these rounds subsonic. The heavier bullets may possible stabilize in the 1:10 barrel if the rounds are kept super-sonic. This is something you'll just have to experiment with.
Subsonic rounds are extremely difficult (if not impossible) to cycle in an AR even with the adjustable gas tube. With the adjustable tube you can simply close the gas port off and cycle the AR like a bolt action with the charging handle, when using subsonic rounds.
I've dreamed of building a .300 Whisper for years on either an AR or a bolt gun. At this point, a bolt gun seems to be the more logical choice for me. The Savage platform would make this project a very in-expensive and easy custom project.
Good luck on your project. Keep us informed on the developments.
