In the FBI ballistics thread, we started to touch on .300 Blackout over 5.56 as a choice in terms of close range defensive uses, particularly in the context of short barrels and suppressed used.

I think that's a conversation worth having, fresh and new for 2026. Why? Well, if you have been under a rock or ignored all things NFA because it's complicated and you don't want to ask permission and all that, basically short barrels and suppressors are back on the menu. It has only gotten more complicated, but the simple version is that there was never a better time to get in on it.

Ok, so I have ignored .300 BO up to now. Why? Well, the subsonic ammo is expensive and it's not as quiet as subsonic 9mm for my purposes. The terminal ballistic data I've seen isn't impressive enough over 5.56 to warrant me paying more to get a little quieter for a defensive round.

Am I wrong? I'm open to having my mind changed on this as I have several cans I could use on a .300 BO SBR that would do great. I just feel like it's an odd splitting the difference thing over the two calibers I tend to like to shoot suppressed in SBR's, and it's expensive. My one oddball fun caliber that also doesn't do anything better than 5.56 or 9mm is 5.7x28, and it both suppresses really well and currently doesn't cost any more than 5.56 does.

I think let's also open it up to discussion of LE agency use, because it's relevant in the grand scheme of things.


Video for giggles because the algorithm decided this morning that I needed to see and hear this.

For close range defense, hard to beat suppressed 9mm Luger or .45 ACP. As the range extends, the 300 BO will retain more energy.

Some interesting gel testing results. 300 BO subsonic frequently tumbles on impact with the gel.

https://www.ammoman.com/blog/s...blackout-ballistics/

Thanks for starting a new thread, P220 Smudge.

I look forward to reading the comments like those touched on in the other thread.


I have zero interest in subsonic .300 and would choose a MP5 or something similar if subsonic in .300 Blackout was my only option. For me, the benefits of .300 Blackout have more to do with having rifle performance with supersonic ammunition in a very short package without the insane blast of 5.56 or loss of performance. You can certainly add a suppressor to a 11.5" 5.56 but you then start to loose the benefits of having a shorter barrel in the first place. I've heard complaints from folks who are using short 5.56 rifles during training indoors and even doubled up with ear protection, it's not pleasant.

quote:

Originally posted by Jupiter:
Thanks for starting a new thread, P220 Smudge.

I look forward to reading the comments like those touched on in the other thread.


I have zero interest in subsonic .300 and would choose a MP5 or something similar if subsonic in .300 Blackout was my only option. For me, the benefits of .300 Blackout have more to do with having rifle performance with supersonic ammunition in a very short package without the insane blast of 5.56 or loss of performance. You can certainly add a suppressor to a 11.5" 5.56 but you then start to loose the benefits of having a shorter barrel in the first place. I've heard complaints from folks who are using short 5.56 rifles during training indoors and even doubled up with ear protection, it's not pleasant.

This is pretty much where I’ve landed. I don’t shoot Subs and I’ll probably never get own a can, but I love shooting 300 BO Supers in my DD PDW. I prefer it over 5.56 for a dedicated 0-200 yd compact rifle. For my needs, it’s like having the equivalent to a 7.62x39 but in a more modern, compact package that fits in a backpack.

Even with mine having a 7” barrel, I don’t find it to be obnoxious at all for indoor shooting with regular ear pro.

.300BO’s versatility has always impressed me. A round that is effective in light supersonic AND heavy subsonic rounds gives the shooter a lot of flexibility.

The 8”-ish suppressed platforms with 220gr subsonic rounds drew my interest. An AR upper as such is on my ‘want’ list. It was Sig’s 5.5” Rattler though that won me over. A couple of years ago I snagged the pistol version. While there are suppressors that can tame this with subs quite effectively, I keep it loud with Federal 120gr HP Powershoks. These group better for me than Hornady 110gr V-Max, and it is notably milder compared to 7.5”, 10”, and 11.5” 5.56mm ARs.

This is a handy package, and adding an Eotech XPS and Surefire M340 has given me enough features in a road-trip carry. Already having 5.56mm, 7.62x39mm, and .308 kept me from .300BO for a long time, but I have no regrets adding it to the lineup.

Yeah, the difference between 147gr 9mm and 220gr 300BLK at the same velocities really isn’t worth the 5x price difference in my opinion. Plus, I suspect the 9mm bullet is better designed and understood at those velocities than the less common cartridge, but I’d love to hear somebody more knowledgeable than I on that.

The big value add of 300BLK for home defense is the ability to go to significantly shorter barrel. Seven inch barrel plus a suppressor is as handy as 11.5” without.

Personally, I’m sticking to .223 for home defense because I prefer the light, high speed bullet in a drywall house than a slow, heavy bullet.

Most of us already have a bunch of 9mm firearms. The ballistics of the 9mm from a longer barrel will be better, of course not up to 300 BO levels.

The 300 B.O. description often includes better ballistics out further than the 9mm, 100 yards +, but this discussion is geared more toward H.D. ranges.

For these reasons & likely others a 9mm PCC makes sense to me, before stepping up to the 300 BO. On top of that, most of us have a handful of AR’s with medium or shorter barrels.

I've shot some .300Bo and almost always a shorty and always suppressed. I'll admit it's a cool set up when done right. I have this strange aversion to new calibers. I also think, in my brain, it serves the same purpose as a 5.56, and I'm no longer interested in that sort of redundancy. I'm just now getting serious about a bolt gun after 8 years of looking.

I know some folks who hunt with it and love it. For me, I cant warm up to the idea of investing in the caliber.

To those that have a lot of experience shooting both .300 blackout supersonic and 5.56 suppressed, is there a noticeable difference in gas blowback to the face and how dirty the weapon becomes?

The Nosler/Noveske and SSA loads in this article are likely near-identical to the Nosler #61050 that I have chosen for my "performance" .300 ammo.

https://www.recoilweb.com/300-...rs-guide-137705.html

As stated in another thread, I had bad luck with SubX in my gun, in the form of what looked to be accelerant particulate fouling the action. In pursuit of something as accurate, boasting low velocity terminal performance, and cleaner, I settled on the Nosler. It's expensive. I don't shoot it often, and use Winchester "Super Suppressed" as my practice ammo.

My gun uses an 8.3" Ballistic Advantage barrel and AAC SDN6 silencer.

I have a Noveske Chainsaw SBR in .300 with a Deadair Sandman S. Shooting Hornady subsonic out of it you honestly don't hear a lot more than just the bolt cycling, it's super quiet. I've got a Mojave 9 suppressor for my 226 but haven't had the chance to shoot subs out of that but looking forward to it.

A recent thread that's relevant to this discussion...

https://sigforum.com/eve/forum...0105858/m/1460022125

quote:

Originally posted by Jupiter:
To those that have a lot of experience shooting both .300 blackout supersonic and 5.56 suppressed, is there a noticeable difference in gas blowback to the face and how dirty the weapon becomes?

I have enough experience tangentially or by association, however you want to look at it, so weigh in and say this is more host and suppressor dependent than caliber once you start getting up to modern rifle calibers. Pistol caliber subsonic ammo tends to have a lot of fillers in it to have enough powder volume in the case to ensure ignition at all angles, and a lot of that stuff just turns to burned crud in your firearm, which blows out every which way when you shoot. Not as much the case with rifle ammunition as I understand it, and that's maybe a whole other topic. But for sure with rifles, gas to the face is a backpressure thing by and large, and is mostly dependent on gas management in the host and what the can is.

quote:

Originally posted by KSGM:
A recent thread that's relevant to this discussion...

https://sigforum.com/eve/forum...0105858/m/1460022125

I read through it and I would say that modern ultra-low backpressure suppressor designs that weren't available to you would yield a totally different discussion. It just isn't the case anymore that port pop cannot be all but eliminated from semi-auto designs with the right can. I've experienced it. It's real.


This is all relevant to my interests, but it also kind of tangential. The gas to the face thing and port pop, fouling and all that stuff, it's manageable by enough other means that I'm personally unconcerned with the peculiarities of .300 BO in this regard. I'm far more interested in the ballistic "why should I?" If that makes sense. If it's primarily that it has comparable terminal performance to 5.56 at closer ranges with supersonic ammo at much shorter barrel lengths without as much concussive force when suppressed, then I can see a use case for it in my world. The "it's really quiet with subs" as an afterthought wasn't really the angle I was coming at it from, but when I look at it that way, it makes more sense. The real question is what is that buy-in, and is that worth it to me. I guess I need to start looking into this. I have a really nice, super-low backpressure suppressor that sounds phenomenal on a friend's MCX in .300, and balances nicely, too. I could probably be ok with something comparable.

The fact that subsonic .300BLK is reliable (and quiet) in a compact semi-auto carbine is the crux of the caliber though, isn't it?

The video you shared in the OP was about noise, after all. And it is compelling.

It has performance advantages outside of that, as you imply, but, even if the cost was the same, it lacks the practical "battlefield ubiquity" of 5.56.

The CQB terminal and concussion performance are compelling, I suppose. And I'd be interested in that scope if I was a member of an LE entry team, or if I had the ability to practice in a shoot house environment with regularity as a civilian, and wanted to maintain that niche in my "preparedness arsenal". Which I suppose I do already, outside of keeping supersonic .300 ammo on hand.

I have minimal interest in supersonic .300 performance or application because of the cost and lack of prevalence, when compared to 5.56.

I have an old Aero 8" SBR(twas my first!) which was intended for 100% supersonic and suppressed use. 8" Still gives 1000+ foot-lbs of muzzle energy, which is substantially more than 5.56 at the same length. It is super duper handy.

Mine has almost no blowback with the Radiant, I guess I got lucky with the port sizing. It is loud with supers, but not as loud as 5.56.

One thing I did not expect was how much fun subs are. It's a true DI gas-operated system, so it can be very quiet with subs. You don't even need a great can. Sometimes I bite the bullet, (haha) and buy subs when I see good ones available. Sounds like I need to grab some winchester suppressed ammo.

This message has been edited. Last edited by: DoctorSolo,

I went through the time, trouble, and expense to get a Galil ACE 2 5.56 SPR'd and I'll readily admit that it was a mistake. Waay too noisy and the concussion from the muzzle blast is extremely uncomfortable, even with a decent suppressor. On the other hand, I picked up two .300 BOs (a Tavor X95 16" bbl and a 9" bbl PSA Jakl), that shooting subsonic ammo is a pleasure and when I switch to supersonic, they function well and are very easy on the ears. From here on in, if I go with a rifle caliber, short barrel, suppressed long gun, I'll be the .300 BO.

quote:

Originally posted by pulicords:
I went through the time, trouble, and expense to get a Galil ACE 2 5.56 SPR'd and I'll readily admit that it was a mistake.

I did the same thing with a Galil ACE pistol in 7.62x39 when they first came out a number of years ago. Unfortunately, I had to send it back to IMI and cancel my form 1 after the ATF decided the ones originally imported by IWI were machine guns. Even with the extremely short 8.3" barrel, it was not obnoxious and still fun to shoot. Like stormin said, .300 Blackout is " the equivalent to a 7.62x39 but in a more modern, compact package that fits in a backpack." But enough about my 7.62x39. P220 Smudge might beat me over the head if I start to hi-jack another one of his threads with 7.62x39 thread drift

quote:

Originally posted by P220 Smudge:
I have enough experience tangentially or by association, however you want to look at it, so weigh in and say this is more host and suppressor dependent than caliber once you start getting up to modern rifle calibers.for sure with rifles, gas to the face is a backpressure thing by and large, and is mostly dependent on gas management in the host and what the can is.

Thanks for the feedback, P220 Smudge. I'll be the first to admit I'm not a suppressor expert.
One more question. So if comparing let's say a 8" .300 to a 8" 5.56 using the best suppressor technology for each caliber and the most common supersonic ammunition and same overall length of the weapons, the results would be close enough to make no practical difference when it comes to blast, gas to the face and performance of the ammunition?

I bought an 11.3" 1:7 twist Wilson Combat 300blk upper before one of Colorado's legislative attack on ARs, then made a lower an SBR. I later bought a Wilson 9mm AR-pattern with an 8" barrel. I have .223 AR15s with barrels from 14.5" to 24". I've shot a variety of factory ammo in all of them, and all are suppressed.

Part of my 300blk choice was to find the longest SBR barrel that MV for 110-150 grain supersonic factory loads was under 2200 fps, which is where I start seeing dings & dents in my steel targets. Thus, I wanted to be able to shoot AR500 steel as close at 5 yards without damaging the targets. MV testing showed that I can shoot 120-150 grain loads up close, but the 110 grain loads run 2200-2350 fps, and thus need a little distance to the plates.

I knew that a 1:7 twist was a compromise -- a little faster then necessary for supers, a bit slower than optimal for subs. I found accuracy for the 140-150 grain FMJ loads wasn't great. At 100 yards one group could be 1.5" and the next over 3". Dispersion tended to be similar in both vertical and horizontal. My 223 ARs shoot 55 FMJ more consistently.

300blk subs -- even loads with HPBT match bullets -- were even worse in accuracy than the mid-weight FMJ loads. The heavy subs showed little wind deflection, and had minimal horizontal dispersion in calm conditions. But their vertical dispersion sometimes sucked -- at times 2-3 times more than the horizontal dispersion. IMO the heavy subs were OK to 50-ish yards, but beyond that they didn't meet my expectations. I tried them at distance, too. 12" plates could be very hard to hit at 200 yards, even with good dope from prone. I regularly saw keyhole hits on plates at 200 yards, which means the bullets were unstable. This could be an issue with barrel twist.

I experienced multiple factory loads with 125 grain match-type bullets that popped primers. The number of jams were maddening. I had no idea how many places an AR could get fucked over by a loose primer. Ultimately I've settled on 2 factory loads -- Hornady 110 VMax and Aussie Outback 125 SMK, both of which are quite accurate and cycle flawlessly. The Hornady 110 is a hot load, the Aussie 125 is a mild load. Both have produced 1 MOA accuracy out to 400 yards.

The Aussie 125 load has muzzle energy of 1162 foot pounds from the 11.3" barrel. This is close to the 1153 foot pounds that my 16" barrel AR does with 223 Hornady 75 Black HPBT. Most of the 120-125 grain 300blk loads that popped primers had higher MVs, and their muzzle energies were in the 1200-1250 ballpark. That's in the ballpark of my 223s with 18-20" barrels.

The Hornady 110 Vmax produces ME of 1345 foot pounds. It's a hot load, but I experience no primer or cycling issues. I've dug a number of bullets from dirt and they expand nicely -- not the explosive varmint-type expansion that can occur from a 308 Win rifle load. I agree with unscorpsman's assessment that the 110 Vmax is a decent pig bullet. IMO the 110 Vmax from a 300blk SBR could be one of the most effective moderate-recoil HD loads. The noise levels from my 10.3" suppressed 300blk are noticeably less nasty than the noise from a suppressed 11.5" 223 AR15. Still, I won't shoot a suppressed super load in my 300blk without ear pro -- the loads are beyond hearing safe due to the supersonic crack.

Bottom line -- an SBR 300blk with the right super load has a lot to offer.
****

On to my 8" Wilson Combat AR9G -- Glock pattern 9mm. This is truly a great rifle. Light in weight, accuracy that's head and shoulders above most 9mm PCCs, minimal recoil that belies its blowback action, flawless cycling with multiple loads. I have not needed to fuck around with the Wilson to make it work for me -- everything is factory, everything works, I have no need to buy improvements. I've shown the pic where this gun produced a 10-round group with S&B 115 FMJ that was around 2.5" at 200 yards. I consider this a better option than a 300blk with subs for HD. The AR9G has ME of 458 foot pounds with the hot S&B 115 loads. Most of the factory loads produce MEs of around 400 foot pounds -- with 115 or 124 or 147 grain bullets. Now my 300blk produces MEs of 500-525 foot pounds with heavy subs. Higher ME than the 9mm loads, but not signficantly higher.