I would like very much to expand my AR15 hobby by adding another caliber, and have narrowed my search to either the 300 Blackout or the 458 Socom.  Despite the enormous ammo costs for the 458, this would be my first choice, in a RRA upper.

But here is my question/dilemma regarding both rounds: Are they going to stick around? I don't reload (yet), so I will use factory ammo.  I cannot afford to buy a platform where ammo dries up!!

No specialized purpose for either round for me, just another fun gun.

So, I guess my question is, from a long term viability/longevity stand point, which is likely to endure??? Hopefully both will, but am just seeking the wisdom of those who frequent here before I take the plunge.....thanks

I'd go 300BLK, all you gotta change is the barrel if you ever want to go to 5.56mm

I think both rounds are likely here to stay, as of right now the 300 blk is probably a little more secure in that than the .458.  Reloading is a good choice for both rounds and I am working on getting set up to reload 300 blk, but I have been living on factory ammo for the last year.  I don't own a .458 so I can't speak to current ammo availability and price, but 300 blk factory ammo is a little too pricey to plink with or waste rounds mag dumping.

300 BLK doesn't use anything unique other than the barrel. Brass can be made from 223, projectiles are .308.

Even if barrels stopped being produced tomorrow, it wouldn't matter.

pick your poison neither one of them are going any where . ammo for the 300 blackout is starting to become more avalible off the shelf every day . the 458 socom has been around for along time and appears to be headed for sammi approval this summer .hopefully that will make factory ammo from more suppliers avalible and maybe drive the price down abit. to be honest to get the full benefit out of either caliber reloading is the way to go. .458 diameter projectiles are avalible pretty much any where and the brass will last for ever if you dont get stupid and try to turn it into a 458 magnum. .

I think the .300 Blackout will stay even though it's a caliber I'd get into unless you do a lot of suppressed shooting.  You can get so much more versatility from a 6.5 Grendel or 6.8 SPC.  The .458 SOCOM is probably going to stay around, I wouldn't worry about it too much.  I went the 6.5 Grendel & .50 Beowulf route, I absolutely love both of them and would definitely recommend them.

Personally I have the Variant Bug bad with 6 calibers at the moment. (My two personal favorites are the 50 beowulf and my 7.62x39s) That said the easiest on your pocketbook among your choices is going to be the 300 blackout.  I am finishing up my 3rd 300blk  this time a pistol. and I love the caliber for suppressed fire. That said  if you are not going to suppress it, let me suggest you have a close look at the 7.62x39 Ammo costs are in most cases 1/4 of that of the Blackout and is very close in performance to the Supersonic Blackout.

If I was to do another big bore it will be a 450Bushmaster, again. I have had both 450B and 458S and both will do the job, the 450B is SAAMI so it has more factory support and if you don't reload it is your only logical choice unless you have deep pockets to purchase the 458S or 50B ammo.

The 300blk is awesome little round mainly intended for the subsonic suppressed crowd, BUT the supersonic rounds are great deer rounds for closer distances, I say 200 yards and under. A Fantastic round from my Encore, but marginal from the AR15 due to ammo cost with the ability to destroy a "C" note in a hurry,,,LOL Ammo availability is spotty with nothing but chump reloads from boutique handloaders for plinking

Neither would be my choice for a primary weapon, but having multiple uppers that shares a common lower with your 223/556 rifle is how I'd go..

The .300 is definitely here to stay.  More and more companies are producing barrels and ammo for it.  In a short barrel suppressed, it really shines.  But it is also a great hunting round for closer distances.  I use it in a 16" to hunt deer (200-300yrds max) and it is devastating if you use the Barnes TX or the Hornady red tips.

I think they are both here to stay but variant cartridges are always going to be a reloaders game. Even if you aren't currently a loader I recommend it to save a lot of money over time. I could buy blackout loaded for almost $1 a round or I can keep loading my cast rounds for 11¢. As you can see the cost of equipment can be offset quickly.

Both rounds will be around in a niche capacity for a long time. However,

1. Don't you buy ammo online? In which case availability is much less of an issue than most make it out to be

2. Start reloading. You'll learn a great deal about shooting, your accuracy will increase, and you can save money on ammo (caveat being is that you dont save much on 5.56 plinking ammo, so i just buy whats on special but i do reload for precision / hunting 5.56)

I can reload 125gr and 190gr subsonic BO for about $0.35 per round. (could be less if i bought in higher bulk) Either way it beats the shit out of $1 per round. I'm sure 458 is similar

I would agree with many of the posters above...I believe both rounds are here to stay, as there is enough  Industry support for both rounds especially
the .300 BLK. With that said, even most SAAMI cartridges like all the cartridges mentioned so far are really hard find at your local gun shop, and harder
to find at a reasonable price today...So, it is a re-loaders game with most of these cartridges. I believe re-loading is a must in today's economy with the
ever Increasing costs and demand.

One thing that does puzzle me with the .300 BLK round is why it is so expensive on store shelves when you can find them since the .300 BLK is a .223
based round  using cheap and plentiful brass at a average of $1 per round (of course this is primarily due to supply/demand). I have seen for example
6.8mm SPC ammo at a cheaper price-point and more often in stock than the .300 BLK, with both rounds being very popular today and the SPC having a
larger and more expensive case to produce...

The 6.5 Grendel & 50 Beo are fine cartridges, however, they tend to be among the most expensive and hardest to find mostly due to the cost of brass for
these rounds etc.

The .450 Bushmaster is likely the least expensive of the AR big bores and easiest to find over the counter from what I have seen so far in today's market.

The bottom line seems to be that one really must re-load today if one does any amount of shooting/practice or Intends to do so regardless on which
cartridge...Good luck.

Tromix is now making and selling .458 Socom barrels, bolts and related parts.  So, parts are now readily available and at reasonable prices.

And, the .458 Socom forum has lots of loading information, plus info on everything else related as well.  http://458socomforums.com

If you can assemble a standard AR-15 upper, you can build a .458 Socom upper.  The "hardest" part is opening up the ejection port to clear the larger casing, and there are specs and a diagram for this on the forum.

You probably could have built a .458., and purchased all your reloading components with the money spent on factory .300! Then again maybe not depending on how much you shoot. With the blemish bullets I've purchased, great deals on powder, primers bought on sale, brass I already have from .223, and my .300 is only costing me about $.20 or less a round!

 

IDK, I've got about 800-1000 rounds of various 300 blk around, and have only shot 100 or so rounds so far. I just haven't been too motivated to get started reloading.  I haven't been trying real hard to find it, but the lack of powder is what's holding me up right now.  Once I get some powder I'll pick up the rest of the equipment I need for reloading.

PowderValley.com has 8# jugs of 4227 right now and that is good for every projectile you can load in the .300 $154! The Hodgdons website has load data and the velocities are great with that powder for every grain.

I keep hearing that Beowulf ammo is so much more expensive than the other of the "big 3", which has never been my experience, so I started looking at the various online sites for ammo and was pretty amazed by what I found.  First thing was I found no Beowulf ammo in stock at the various places I checked which is unusual, I've never had any problems finding it before today.  However, just looking at prices the Beowulf ammo was priced lower than any of the others or tied with the lowest priced.  The .458 SOCOM was by far the most expensive, almost triple the price of .450 and .50 in many cases.  Far different than what folks quote online when they are recommending their favorite over a Beowulf.  In real life the .450 Bushmaster and .50 Beowulf have very similar prices and are quite a bit cheaper than the .458 SOCOM which was $2.25-3.50 per round.  

I've not started reloading yet so I buy factory ammo and for FMJ "plinker" (if you can call .50 caliber FMJ "plinker") it's about $1 to $1.10 a round which isn't that bad for a big ol' bear dropping bullet.  I do have a couple boxes of the big 350 grain solid brass spritzer stuff that's $2 a round but there's really nothing in north America that won't be dropped with the "cheap" stuff.  I do keep all my brass from my .50B, 6.5G, .223/5.56, .30-06, .45 Colt, .45acp, .40S&W, 9mm so I'll have a start when I do have the room and money to build a reloading station but for now it's all factory.

where are you finding beowulf ammo for 1.00 a round ? I bought some rainere 334 grain for 1.60 per round but thats been it .  so far the 50 beowulf has been a side bar for me I have alot of other projects I been working on but I will soon get some dies and start reloading for it . I agree the 458 socom factory ammo is way to expensive , but so is everything else in my opinion . I dont buy it for the most part and odds are I will never buy any more factory ammo for the wulf either . I have bought  5 boxes of corbon 458 socom ammo when I first got my 458 socom and reloaded ever since , the same for the 300 blackout I have bought 3 boxes of factory ammo and never another . If a person is going to shoot any ar15 variant then a reloading press only makes sense  . I prefer to roll my own ammo anyway since I know the Q.C. guy .

build a Mega MATEN 308 you would love it I shoot mine every week

love the thing is flawless

I buy it locally but even off AA it's only $26.49 for the FMJ 20 round box which is more than a buck a round but still WAY less than the .458.  I bought mine in bulk from AA right before the ammo craziness but I still can get it locally for $23\box of 20.  The hollow points and stuff cost more but there's nothing in NA that won't go down with .50 Beowulf FMJ.  Pretty affordable when you consider the price of .45-70 and other "big game" ammo.

I plan on getting into the reloading stuff as soon as we can make the space and source some affordable equipment, hopefully that'll drop the .50's down 25% at least.

thank you . 45/70 is not to bad but I reload it also  . I buy .458 bullets in bulk to feed the 458 socom and the 45/70 . I live in missouri and a lever action rifle is required by law   . if you start to reload a good single stage press makes loading the big stuff alot easier .

I have both 300 BLK and 458 SOCOM

The 300 BLK's are 16" and 8".  It is great suppressed and good to 200 yards or so for hunting with supersonic ammo.  I reload for it, which is the only way to go.  I can load 150's for under 25 cents per round and 125 gr TNT's at slightly over 30 cents per round.

I just put together a 458 SOCOM with Tromix parts last month.  I can reload for it using new starline brass and 300 gr HP's for $1.50 per round.  New brass is around 80 cents each, so the next loading only costs 70 cents.  Folks on the 458 forum are gettting 12-15 or more loadings on the brass and it is still good to go.

Both of these cartridges are a reloader's proposition in my opinion.

If you do not reload for any of the big bores you are missing out.  I can reload the 458 for less than $.65 each using bulk 405 remington bulk bullets.  If you use cast lead with gas checks you can go even cheaper.  It is not like shooting the 223 but neither is the BO.  I have grown very fond of the ar15 variants.  Go ahead and take the plunge.  Just be prepared to become very addicted.

I just never was the need personally for a 300 BLK. I don't foresee the need to have to have a dedicated subsonic round like that. I chose the .458Socom over the other heavies because of the huge assortment of bullet choices. And if I found a need, I could still work up some subsonic rounds with some REAL punch.