Gunsmithing Question regarding building a 300 blackout

[CardiacKid]

I've been kicking around building a semi-auto 300 blackout for a little while now. I was really interested in the 300 whisper when I'd first heard about it, however it seems as if AAC has marketed theirs a little better and at least a handful of reputable reloading companies are readily marketing dies, etc. to meet the growing demand.

If I were to build a 300 blackout upper, is it simply a matter of purchasing a 7.62 barrel with a chamber reamed for the 300 blackout and mounting it with standard AR-15 components for the rest of the gun or are their other considerations that would require a tailored ground-up build? Being that it's a cut and necked down .223 casing, I would think that any .223/5.56 BCG and upper would work, however I don't know if there are any pressure variances between the two cartridges that would require different weapon components. Also, would it require a different buffer tube, different weight buffer, spring, etc.? It would be awesome if it was just a matter of purchasing a new barrel and then using AR-15 components for the rest of it.

Thanks

 

[AXEMAN]

Re: Question regarding building a 300 blackout

there are whole forums dedicated to that caliber and those topics. i had to ask alot of people those same questions and do a lot of reading to figure all that out. searching stuff here and on the web, using 300 blk and 300 whisper as keywords. man i really had to read a bunch of stuff to get it figured out. if you reload either is good. if you dont and its affordable and available, the 300 blk sounds nice. i know quarterbore has a section of reloading data on the two of them. wiki has the specs on them. ive seen barrels from $165 to $565 and complete lowers for $450 here used.

i had some say i needed to change stuff in my lower and quote me $650 for an upper. i have had others say they did nothing to their lower. i have seen the barrels in pistol and carbine gas. i was told pistol gas is best if you want to run supressed. so far everybody says just build the upper and slap it on the lower. no one mentioned buffer mods, but a heavy buffer is available from slash. he is the goto guy.

 

[Mike308Bell]

Re: Question regarding building a 300 blackout

I built mine about two months ago. I actually have a .300/.221 barrel, but it is the same as the .300 BLK.

Every thing but the barrel is .223 AR.

Build Specs:
DPMS lower, Palmetto State upper and parts kit. Bravo Co. bolt group and upper parts. Gunfighter handle. Magpul butt and grip. Midwest Ind. 12" SS tube. Palidin Machine adjustable gas block and 16" barrel with the port in the pistol position. Got ProMags, GI mags, H&K mags and a few Eagle Mags I borrowed from my AR180....Topped with a Leopold CQ/T Not counting the scope, I got about $1100 total in the gun.

 

[CardiacKid]

Re: Question regarding building a 300 blackout

Thanks for the heads up guys and great looking build above. I'll keep looking for the forums dedicated to that caliber. Wanted to try here since the rampant BS and urban legends are quelled pretty quick by this forum's members unlike some other sites. You guys brought up some points I didn't think I'd have to look at: I'm sure someone's figured out an optimal twist rate for the barrel and popular bullet weights, but I didn't think a pistol length gas system would be preferred - who would have known. Ideally I'd like to run suppressed eventually, but that's opening up a whole other can of worms I don't have cash for right now.

 

[Mike308Bell]

Re: Question regarding building a 300 blackout

Thats the reason why I got the 3way adjustable gas block since the barrel was already ported for pistol for subs when I got it. It will be awhile before I can put a "can" on it. Plus, with it in the pistol postion.....I can still go to an SBR if I wanted. I try to plan ahead....something I learned in the Boy Scouts

 

[AXEMAN]

Re: Question regarding building a 300 blackout

1/8 is the twist people are saying is the best for heavy bullets and thats subs and supressed, and it will shoot the rest too. so search "300/221 ar barrels" or "300 blk ar barrels" or "you get it now" and you will find the barrel. you may want to start to reload anyway