I am very interested in learning what it would take to build a .300 Whisper/Fireball AR-15.

First, can anyone tell me which companies they know of which build these Uppers or Barrels ?

I am a newbie at this, but I would really like top learn more, and from what I have been able to see so far, making an AR-15 in the Whisper/Fireball requires a new barrel (Duh), but I would also like to know what OTHER changes need made to the Upper Receiver to accomodate the new caliber ? Assuming that the magazines hold and feed the .300 rounds, do any other changes need to be made ? Does the bolt carrier or the bolt itself need to be altered ? How about any other internal Upper parts ?

Is it possible to just change out the barrel on an AR-15 and now you have a converted .300 Whisper/Fireball ? And do any changes need to be made to the Lower to accomodate the different caliber ? What about some of the other conversion calibers (.458 SOCOM or .50 AE Beowulf) ? What changes need to be made to a standard AR-15 to accomodate any of these calibers ?

I would greatly appreciate ANY and ALL advice on this matter from anyone. I would especially like to hear from anyone who has experience building a Whisper/Fireball or SOCOM or BeoWulf.

Thanks,
Matt
Alaska

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Welcome to the board.

For many of your questions, try here:
Quarterbore's .300 Whisper pages

Is it possible to just change out the barrel on an AR-15 and now you have a converted .300 Whisper/Fireball ?

Yup. same everything else, due to the same base dimension as the .223, just shorter and necked-up to take .308 cal. bullets.

Cheers, Otto

Is it possible to just change out the barrel on an AR-15 and now you have a converted .300 Whisper/Fireball ?


Yup. same everything else, due to the same base dimension as the .223, just shorter and necked-up to take .308 cal. bullets.

Thanks Otto.

Otto (or anyone else) :

Does this mean the same is true for larger caliber conversions ? For a .458 SOCOM or .50 Beowulf all that is needed is to replace the barrel ?

Thanks,
Matt
Alaska

Zeme, the .458 SOCOM, .50 Beowolf have larger case head dimensions, so they require a bolt change.  The mags may need some tweaking, and IIRC, the mags essentially become single stack.

AFAIK, The 300 Whisper/Fireball/-221 is the only odd-ball cartridge for the AR that uses the same case head size (and thus bolt).  

Matt,
 I just had my C3 dealer build one for me a couple of months ago.  I use the same bolt from my M16 .223 in the Fireball.  He had  to try several different loads  to find one that the rifle likes but now I use a load from AL Ammo and it works and functions flawlessly.  It is truly amazing to dump a magazine on fullauto thru this upper. It is very queit and mine cycles slow enough (with rate reducing buffer) to really have some fun with.  Good Luck

Thanks everyone, you've answered some questions I've had for quite awhile.

I've owned several lightweight AR-15's and I am specifically interested in building a quiet, lightweight AR-15 based rifle in a higher caliber than .223. Originally I thought about going with a higher caliber than .300, but one of the things I am considering seriously is the addition of a suppressor. I know it's expensive and a pain to get the paperwork thru, but I really like the idea of not having to wear a lot of ear protection and the (slightly) increased accuracy and reduced recoil that goes along with fitting a suppressor. Besides ... it's something new and unusual :)

In the higher calibers, the Beowulf evidently does not come in a twist rate that works with subsonic cartridges, and in any case, the ammo is QUITE expensive. The SOCOM might possibly be adapted, but the ammo is even MORE expensive. The .300 Whisper/Fireball seems like a fairly good choice for what I want ... quiet, relatively low recoil, inexpensive ammo (thanks to the ability to convert .223 brass). It also gives me an excuse to learn more about reloading.

There appear to be several lightweight AR-15 lowers on the market, the FAR-15 (4.9 pounds for the complete rifle), and Carbon-15 (3.9 to 4.3 pounds complete from Bushmaster) come to mind. I've owned several of the C-15's and I absolutely loved the low weight. According to BM tech support, the C-15 is not completely compatible with a 'normal' AR-15 design but "if using the Carbon 15 lower with its short buffer system you would need the shorter Carbon 15 bolt carrier and action spring" to match it with an AR-15 upper. The C-15 lower is a phenomenal 0.9 pounds. My goal, if possible is to get a suppressed .300 in the range of 5 to 6 pounds. For the subsonic stuff, I would also like to use an adjustable gas block or tube to have the ability to switch between sub and super sonic ammo.

Anyways, that's my plan ... just gotta wait till I get more info (and permission from the wife :))

Any advice and/or suggestions always greatly appreciated.

:D

Matt
Alaska