The obvious first option is to contact JD Jones at SSK Industries. JD coined the name "Whisper" and made the cartridge famous. I've never heard a single complaint about his work and you will receive a first class firearm, but you will pay BIG bucks to get a gun from JD!!! While it deserves to be the first option, I think it's the least desirable for the individual with a limited budget... But, check out his website because it has tons of great stuff, including VERY cool guns and proprietary wildcats.
The third choice is to build your own. You can buy the barrel from OlyArms, or have one chambered for you if you want a custom twist and/or better quality steel. Randall Rausch at AR15Barrels.com makes a lot of custom barrels and would be an ideal choice to help you get the right barrel for your application. Then match it with the upper, hand guards and gas system of your choice and you're ready to go. If you've ever built an AR upper assembly, this is no different; that's the charm of this cartridge, you don't need a custom bolt or mags!!! This is probably the best choice because you can assemble the upper just the way YOU want it. Quarterbore's 300 Whisper project is a good example of building an upper from the "ground- up". My Gunsmithing Links
and AR-15 Links pages should have the necessary links to find the parts to assemble your dream rifle.
I’m assuming you’ve decided what you will be shooting through your gun: lighter bullets for hunting (125-180 grains), heavier bullets for sub-sonic fun (200-250 grains), or maybe you want a gun that will handle both? The chart below is a collection of information provided by people a lot smarter than me, people who understand the complicated interaction between roational forces, velocity, bullet length, bullet weight and things that make my little brain hurt. Thanks to the ballisticians and bullet manufacturers that know their craft and were gracious enough to share information.
The chart lists the minimum twist required to achieve stabilization for loads that stay below the speed of sound and those that go super-sonic.
Do I need to make any changes to my .223 magazines for them to function with 300/221?
No, your regular mags will function with the 300/221. The case has the same negligable taper as the .223 case and they double-stack perfectly. If the spring, follower and feed lips are in good enough condition to reliably feed 5.56, you will be in good shape with the 300/221.
.223 REM vs .221 Fireball vs 300/221
Case
Case Head Diameter
Base Diameter
Base to Shoulder
Taper from Base to Shoulder
223 REM
.378
.376
1.434"
.827 degrees"
221 Fireball
.378
.376
1.066"
.752 degrees"
300/221
.378
.376
1.066"
.752 degrees"
Information taken from chamber reamer specs on Clymer Tools website.
Can I buy ammunition or do I need to have the ability to reload?
The numbers speak for themselves. To my knowledge, the only manufactured ammunition is from CorBon. Here is the way their prices stack up against my cost to reload. My reloading costs include the purchase of new 221 Fireball brass, the number in parenthesis is the cost to reload minus the brass:
Factory CorBon 125gr @ 2100fps - $16.72 per box of 20
Reloaded 125gr Sierra SP @ 2250fps - $9.09 (4.42) per box of 20
Factory CorBon 220gr @ 1050fps - $18.04 per box of 20
Reloaded 220gr Sierra HPBT @ 1050fps - $10.81 (6.14) per box of 20
Even accounting for the purchase of new brass, the greater than 40% decrease in cost more than justifies the purchase of dies and the time required to reload. If you're going to shoot alot, you can't afford not to roll-your-own.
