Scroll through defensive ammo recommendation threads here and all you see are 5.56 and 300 blk.  Is there a reason people aren't using beefier cartridges for HD like 458 socom?

*Edit* Okay, all useful replies thus far, but mostly answers are convenience/cost related or "good enough". Allow me to steer my own thread a bit (should I start a new thread?).  I've got existing 5.56 and .308 platforms, but thinking of what could improve.  I have no doubt either of these cartridges would subdue a would be invader, however I would like to maintain situational awareness and communication with fellow inhabitants without having my ears ringing from a Mach 3 projectile indoors without ear pro.  This makes me think a subsonic suppressed option would be nice.  Subsonic 300 blk is throwing a 300 gr bullet at 1000fps, which in terms of energy on target is in the realm of 45 ACP, oof.  458 socom can sling 600 gr lead and reloading components are plentiful.  To swap to either 300 blk or 458 socom, I'd probably build/buy a complete upper.

Seems like there must be something I'm missing or more people would be running it.  Is ear ringing from firing indoors without ear pro not that bad? Haven't actually tried it. Does a 300 gr subsonic round somehow have decent terminal ballistics, through barriers, etc.? Is reliability horrendous?

Availability and cost.

2-legged critters aren't that hard to kill

Let me count the ways:
1.) Cheap
2.) Effective
3.) Available
4.) Less over penetration
5.) Less recoil
6.) You can train with them and not have to take out a second mortgage...
7.) Firearms tend to be more reliable (AR platform designed for them, or at least their rim diameter)

Thanks for the replies fellas, I've added some more details to the original post to further discussion.

300 Blackout doesn’t run 300gr bullets that’s usually 338 and up weight.

There’s more to it that simple energy calculations. Bullet choice is important. A 600gr 458 bullet is probably a horrible choice for most HD stuff because of extreme over penetration. We do have quite a few dedicated expanding subsonic bullets from places like Lehigh Maker Hornady etc. those are good to compare.

The reason most people use supersonic is because they are so much more effective terminally.  You’ll never get the same performance from subsonic stuff so you just have to decide if the compromise is worth it. The reason most people use 556/223 is because it’s cheap effective and has good capacity with standard AR mags. Something like 458 socom holds a whole lot less rounds and that’s important to a lot of people.

300 Blackout is in the 220-240gr range.

Here's a Maker 375cal 325gr Subsonic Expander fired from a 375 SOCOM.  Often referred to, as the Trifecta of Doom.

Tony

Damn. What's that measure diamter wise? Looks huge. Do I remember correctly that 375 Socom is your favorite of the Socoms? I don't see as much talk about it but it seems pretty versatile.

you're overthinking it. A supersonic suppressed 556 or 300blk in the house, especially with stress-induced auditory exclusion, will not affect your situational awareness.

If your priority for an HD gun is stopping the threat as quickly as possible (which it arguably should be) then use the best rounds for that job, and then select for additional subsequent priorities. Using subs for HD is prioritizing quietness over effectiveness.

Using 300blk subs for HD are still within the envelope of effective. They will stop the threat, especially if you get specialty expanding rounds. But they won't do it as reliably in as many possible scenarios as supersonic. However, at least you still have 30 rounds on tap (for misses, multiple assailants, or if crap gets really bad- laying down cover fire. lol)

Going to some other round like 458 subsonic might get you better subsonic ballistics, but they still aren't as good as supersonic. And now you've got 10 rounds in a mag. And at least my 458 socom is much less reliable that any of my 300 blks guns.

If my or my family's life is on the line, I'm going to sacrifice everything else to win that battle because if I don't then none of the rest matters.

I’d have to imagine penetration of intermediate barriers with a subsonic 600gr projectile is going to be absolutely stupid.  Something I don’t want in a house with other people in a residential area with other houses.  Any proper defensive load will penetrate a lot, but intentionally choosing something that goes far and above everything else is irresponsible, IMO.

Bottom line, look at what the people who do a lot of short range work  shooting people are using.  5.56 and .300BLK.  Both work well and have their own drawbacks, but suppressed they’re about as good of a compromise as one can get.  Good capacity, good reliability, wide selection of ammo choices, etc.  Subs have a niche they fill very well, but I don’t consider HD to fall into that niche.  Supers only for me.

Short barrel performance
Ease of getting into from 5.56 (just a barrel change)
Excellent Subsonic capability
It is mainstream enough that you can find ammo everywhere.

Can be reloaded using 5.56 brass, .308 bullets and small amounts of pistol powder....thus ammo is always "available" (especially if you cast you own).

uses the standard AR15/M16 BCG

Regarding the OP's performance question on the edit update. The heaviest .300 Blackout subsonics that I would consider normal are 220gr. The 45 vs .300 comparison gets thrown around a lot, but the actual performance of the two cartridges are very different. In additional to grains and velocity, performance is also driven by the bullet design. The spitzer design of .300 blackout can defeat soft body armor and performs very different in testing verses 45 ACP.
I fully agree with you on preserving hearing and communication abilities, especially for these indoor uses. I have 220gr subsonics loaded for that specific reason. As to why not "x", Blackout has plenty of performance, it suppresses very well, it's versatile with supers, and it shares complete magazine and parts commonality minus the barrel,  with the AR-15 platform I already own. There's just no need to chase other cartridges.

Touching off any firearm indoors without ear protection is going to ring your ears and more.  I have permanent tinnitus because someone fired a .45 ACP next to my unprotected ear in an enclosed space, and that is a relatively low pressure subsonic round.  Supersonic or subsonic doesn't matter.  Loud is loud and will cause damage to unprotected hearing.  In matters of life or death, hearing damage may be a secondary thought but don't be so careless to think hearing damage doesn't matter.  During the bad days I wouldn't wish tinnitus on anyone.

As for why I run 300blk as my alternative caliber:  

Performance in a short barrel
Less wear and tear on a short barreled AR than 5.56
Commonality of parts
Eventually a can, but not likely anytime soon given my state's anti gun diarrhea agenda

Go listen to typical suppressed 556 and 300bo, both super and sub (even if you gotta buy some subsonic ammo). Neither are that quiet, unless you throw a lot of money at it and even then, may involve reliably compromises. Frankly 7.62x39 suppresses quieter (doesn’t cycle the bolt without setting up dedicated custom configuration.)
I’ve tried all three of these, both super and subs.

As for rounds like 458 socom , go price a case or two of ammo and see how much practice you’ll be doing.

IDK if PCC in 9mm 147 is reliable, but that’s what I’d be looking into if I had to pick a rifle. Mine would be SBR too. Go try moving around the house at night with full length AR rifle. This lets you not only afford the ammo, likely you got pistol in same caliber, maybe even magazines are interchangeable, a bonus.

To the OP:

There is no replacement for displacement (especially at HD distances), and 110 300blk F@&#’s hard.

Bah, another wildcat, another mag pattern, under powered. A 45 hits harder subsonic and 308 hits harder super and from way, way farther away.

Yeah, I’m pretty sure .300BLK hasn’t been in the “wildcat” category in a decade or more.  

Also, not shocking that cartridges exist that are comparable on the low end or more powerful at the top end.  It’s almost like the cartridge is a good middle ground between those two, somewhat extremes (at least defensively speaking).

Are you suggesting a .308 for HD?

300 BO is a great close quarter rifle. Most shooting are under 300 yards, which the 300 BO shines. Fairly inexpensive too.

ITT we see that some people still don't understand projectile secional density and how it affects terminal ballistics.

300blk was SAAMI approved in January of 2011 (thus no more wildcat) and uses STANAG mags (no new mag pattern).
As for the whole "X caliber does this better, and Y caliber does that better", that type of flawed, drive-by analysis can be done on ANY caliber if you are comparing to two different calibers out of completely different platforms.

I found interesting that the 5.56 V-max round started to break apart (2 significant pieces) after going through 2 walls (4 pieces of drywall with studs between each pair). And then the pieces were stopped by the next (3rd) wall.

And the 5.56 FMJ went through all 4 walls (8 pieces of drywall). Sideways through the 4th wall.

300 Blackout is sex appeal.

110 tac-tx makes it an excellent killer further than it's capacity should allow.

Once you shoot a smooth running Blackout with subs, you will know the rest.