Basic Ballistics: 5.56 NATO vs. 300 Blackout

5.56 NATO vs. 300 blackout

Dan Z. for TTAG

By Matt Sandy

Yes, another 300 AAC Blackout vs. 5.56 NATO article. However, in this one, I’ll compare the two specifically by looking at their ballistics. Ballistics is a broad term that actually covers three subsections: Internal ballistics, external ballistics. Let’s look at all three.

The American-made 300 Blackout was Advanced Armament Corporation’s solution to the problem, “How do we get 7.62×39 performance in an M4/AR rifle with as little change to said platform as possible?” They started with the 300 Whisper, a wildcat cartridge. They got it standardized and approved by SAAMI before changing the name to 300 Blackout.

In order to keep this article at a reasonable length, we will be looking at the ballistics through a set of pre-determined filters. The primary weapon system will be an M4/AR-15 platform with an AAC upper using a 9-inch barrel and pistol length gas system. I will be comparing it against the 5.56 NATO and 7.62×39 Soviet when relevant, as the 300 Blackout is meant to replace one and match or surpass the other.

Cartridges like the 6.8 SPC and 6.5 Grendel aren’t relevant comparisons, because they require a different bolt face and different magazines resulting in decreased carry capacity. By comparison, 300 Blackout only requires a barrel change. From the military’s perspective, that’s ideal.

And it’s probably the most important thing to remember when looking at this cartridge and why it exists. The 300 BLK round is a 5.56 replacement, with 7.62×39 capabilities with minimal alterations required for the weapon system. Let’s look at how well AAC accomplished their goal by analyzing its ballistics. I will also give my opinion on the very simple question, “is it better than 5.56 NATO?”

Let’s dive in.

Internal Ballistics

Internal ballistics covers everything that occurs from the moment the firing pin ignites the primer until the bullet leaves the muzzle. Maybe the most significant application of this is barrel twist rate. In general, the longer and heavier the bullet is, the tighter the twist rate needed to stabilize it. AAC offers 1:7 in all three of their barrel lengths.

This tells me that AAC, the company that has fine-tuned their M4/AR-15 platforms to work with high velocity supersonic ammo and low velocity subsonic ammo, deems this the most versatile twist rate. If, however, you are building your rifle around a specific bullet weight and load, then twist rate is a valid consideration for optimizing that load. If you’re using lighter bullets a slower twist rate can give better performance.

External Ballistics

External ballistics is everything that happens to the bullet between the muzzle and the target. Trajectory, wind drift, velocity, etc. This is what most people refer to when they talk ballistics. The accompanying images show several different common loadings of 5.56 NATO, 7.62×39, and 300 BLK.

The data was generated using ballistic coefficients and muzzle velocities primarily from Hornady. I did this for two reasons.

First, Hornady is a reputable manufacturer. Second, they list all the information I need to generate the data. The muzzle velocities are an estimate because most published velocities use longer barrels like 20 or 24 inches. I subtracted 25 fps per inch until I reached the desired barrel length.

These aren’t supposed to be hard numbers, but general indications of how each cartridge performs. Each cartridge is subject to the same degree of error, since I will be doing the same math for each. Data was generated using the Applied Ballistics phone app, at sea level, on a 70-degree day, 50 percent humidity, a 10-mph crosswind for drift in 100-yard increments.

Supersonic Ammunition: I was surprised by what the data showed here. Across the board, the 300 BLK rounds were only minimally better if not worse than military grade 5.56. (NOTE: After reviewing comments from readers, the author sent us updated supersonic data, shown below).

The 5.56 had at least 500 FPS on the 300 Blackout for velocity, slightly decreased muzzle energy, a little less than half the bullet drop, and less wind drift. And when I say “slightly” decreased energy, I’m talking within 50 ft/lbs at any distance, with the 5.56 actually outperforming 300 BLK at some.

The 7.62×39 ammunition is basically identical to the 300 BLK ammunition. Despite using estimated muzzle velocities, I’m not really seeing any hint of the 300 BLK rounds being better by any significant margin, or at all. Supersonic 5.56 would be my first choice for longer shots.

Subsonic Ammunition: Here I included ammunition primarily from Engel Ballistic Research because they listed all the information I needed for subsonic loads. This is important because the Ballistic Coefficient of a bullet changes depending on the velocity. To be specific, the BC increases as the bullet velocity decreases.

So, using BCs generated from supersonic loads would give us less accurate trajectories than if we used BCs generated from subsonic loads. The 5.56 is the only exception. Atomic ammo doesn’t list the BC, so I carried over the M855A1 BC. Take that as you will. I also threw in 9mm and .45 since they are the primary competition for the subsonic, suppressed role in a short barrel platform.

The subsonic results were pretty similar to each other.

300 Blackout Ballistics

300 Blackout Ballistics

The 5.56 and 9mm fell short in the bullet energy department by roughly 100-200 ft/lbs across the board. This is expected, since the bullet weights are nearly half that of the others. The .45 had the most energy at the muzzle but quickly fell behind as the distance increased.

The velocities were extremely close for all except the pistol cartridges which finished roughly 200 fps slower than the rifle cartridges. The drop rates were also very similar, with the pistols again underperforming. The 220 gr 30-caliber bullets had the best overall performance. The 208 gr Hornady bullet is an odd exception. It had an extremely high published BC, which causes it to outperform the 220 gr bullets by a little.

The disparity in the BCs makes me think that either Engel is underestimating their BC or Hornady is overestimating theirs. Either way, the 300 BLK takes the win for subsonic loads thanks to its heavier bullet and better BC.

Terminal Ballistics

Terminal Ballistics is everything that happens between the bullet hitting its target and it finally coming to rest. I want to start by saying terminal ballistics is very complicated. There are a huge number of factors and variables that can’t be properly accounted for, and certainly not agreed upon.

There is, however, one element of bullet wounding that is universally accepted. When a bullet strikes a body, it will put a hole in that body slightly bigger than the diameter of the bullet. By this logic alone, 300 Blackout rounds are better than 5.56.

Tumbling and fragmentation increase the size of the wound, but the 300 BLK will always have a slight size advantage over the 5.56. When comparing the same bullet design, M855A1 vs M80A1, the 30-caliber cartridge is superior.

Don’t get me wrong, both will kill. And the M855A1 definitely has superior terminal ballistics to its predecessor, but it can’t outperform the larger 30-caliber bullets when comparing similar bullet designs.

300 Blackout Ballistics

300 Blackout Ballistics

Both images above are from The Wound Channel. The M80A1 photo isn’t as clean, but I think it still properly illustrates the difference in wound size between the two rounds. YouTube is full of ballistic gel test videos showing M855A1 and M80A1 performance, including this video which shows the M80A1s effectiveness in the 300 BLK platform.    


I haven’t seen any photos or footage of how the new bullets perform at subsonic velocities, but it’s safe to assume that at worst, they don’t fragment – which puts us right back at the beginning where the bigger bullet causes the bigger wound.

This also means that, technically, 9mm is better than 300 BLK and .45 is the best. If only terminal ballistics were that simple, or I had more room to write. That being said, at close ranges with subsonic loadings, the .30 caliber bullet may be the best choice. It may not put the largest hole in the target, but it has better sectional density giving it superior penetration. This will help it defeat some barriers while maintaining lethal force better than the pistol cartridges.

Also, as AAC intended, if the fight suddenly shifts to longer ranges, it definitely has superior terminal ballistics at range. Furthermore, you could throw in a supersonic magazine that overwhelming surpasses the pistol calibers at range. From a terminal ballistics perspective, the 300 BLK seems to win due to its bullet diameter and range versatility.

I covered a lot, and still only touched on a lot of the topics brought up here. Especially terminal ballistics. Papers are written on that stuff. But, after looking at the numbers, AAC definitely succeeded in seamlessly putting 7.62×39 performance into a standard AR-15 platform. Is it better than 5.56? For range use, I’m going to say no. 5.56 is the best option for reaching out and touching something.

Other than that, I’m leaning towards 300 Blackout as the better option. Especially in an SBR PDW-type role. The 5.56 barely fills that role in a subsonic capacity, and 300 BLK has better accuracy and range options than pistol calibers.

I don’t think 300 BLK replaces 5.56 NATO. The true answer is mission-dependent, but at least we have more viable options.


Matt previously served five years in the Army with 2nd Ranger battalion, 75th Ranger Regiment and is currently a gunsmith at The Range at Austin. He also competes in both USPSA and PRC matches. 


  1. avatar Jack says:

    Give me something as quiet as a MP5SD than can compete with x39 when the bad guys see us.


    It’s not a 5.56 replacement.

  2. avatar Butthole surfer says:

    Andrew at The chopping block/
    has much much much better videos on terminal ballistics using calibrated ballistics gel, clear gel just doesn’t work as good.

  3. avatar Matt in Oklahoma says:

    If your gonna suppress the .300BK If not 556. It also depends on your state laws.
    I hunt, in Free America, all the time with mine as does my family and none of us jumped ship to .300. Within its limits(like any cartridge) it does just fine.
    When I’m moving up it’s to the Grendel or 243 then up from there to 06 and so on.
    More than bickering know your weapon and your true abilities and you won’t have time to think about little barber shop arguments cause you’ll be shooting and hunting.

  4. avatar tfunk says:

    Did I read correctly that velocities were…derived from a load table and subtracting 25fps per inch of barrel loss? 🤦‍♂️

    1. avatar Southern Cross says:

      Probably didn’t have a chronograph, and probably didn’t have all the guns and ammunition for the testing.

  5. avatar Pb_fan59 says:

    Nope… I’m waiting until next week when the Acme 6.33mm Roadrunner Laser Emulator cartridge is released– surely that will put an end to all of these silly discussions !!

  6. avatar Ralph says:

    “Ballistics is a broad term that actually covers three subsections: Internal ballistics, external ballistics. Let’s look at all three.”


    1. avatar Tom in Oregon says:

      Yet another reason why 5/3’s of all Americans don’t understand fractions.

      1. avatar I Haz A Question says:

        LOL, I’m going to steal that, Tom… 🙂

      2. avatar Matt in Oklahoma says:

        I only get it 9/5ths of the time

    2. avatar Lance F says:

      I read that 6 times before i figured out what was going on.

    3. avatar Elmer Fudd says:

      Typographical error.
      Been there. Done that. Don’t get shitty with someone else having a typo.

    4. avatar Ropingdown says:

      He was likely reluctant to mention terminal ballistics, afraid the guys in jihadi training might get the wrong idea and waste their time reading the technical stuff.

      At any rate, there are four relevant ballistic phases, if you include transitional ballistics.

  7. avatar former water walker says:

    I’ll keep what I have…young Kyle sure showed the efficiency of 556(maybe 223)in Kenosha😏. Free Klye!

  8. avatar Prndll says:

    “ Furthermore, you could throw in a supersonic magazine that overwhelming surpasses the pistol calibers at range.”

    What is a supersonic magazine? I’ve never seen that. Where do I get one of those?

    1. avatar Pb_fan59 says:

      Sorry, those are no longer available. From what I understand, they were provided for your in flight reading pleasure while aboard the Concorde, which has been removed from service. Sorry… you snooze, you lose

      1. avatar Prndll says:

        I guess so

        I was starting to think it was just another thing Washington banned.

    2. avatar Baldwin says:

      Pretty much everyone else knew what he was talking about.

      1. avatar Pb_fan59 says:

        This just in…. Chinese hackers have infiltrated the internet and have been successful in completely disabling sarc detectors. Please proceed with caution while posting replies. Thank you! (/sarc)

  9. avatar Elmer Fudd says:

    I confess that I was once terminally unimpressed with the 300 Blackout cartridge. It seemed to me as if someone had gone to a lot of trouble to reinvent the .30 carbine cartridge. The cartridge is pathetic when compared to a .308 much less a .30-06. I understand that bigger bullets generally make larger diameter wound channels. The winding effects from the little .556 is almost magical if and when when it tumbles. However; penetration depth is important. Penetration depth on soft tissue is generally proportion to momentum density or sectional density multiplied by velocity. The .300 generally wins unless you are loosing with lighter weight bullets. However; wounding effect from a bullet that hits bone is proportional to kinetic energy or bullet mass multiplied by velocity squared. If the bullet hits bone, the 5.56 is generally equal to the .300 blackout.

    Since no bullet has any wounding effect if it misses, external ballistics are profoundly important. Most shooters will find it much easier to hit at intermediate range with the faster, flatter shooting .556. However; if you have a fettish for a SBR, the .556 looses this advantage.

    I confess that I was compelled to reassess my prejudices against the .300 blackout last Fourth of July. Everyone brought some guns for some informal target shooting. I was able to shoot some AR-15s chambered in .300 Blackout. Big yawn, until someone put a suppressor on their SBR loaded with subsonic ammunition. As pathetic as the external ballistics are, I could still hit targets floating in the reservoir about 200 meters away once I had a sense of the probable bullet drop. Of course the CZ Scorpion with a short barrel and suppressor was equally impressive.

    While I now am more favorably impressed by the .300 Blackout, it style would not be my first pick for my only gun of the SHTF. My first choice would be either an HK-91 or an M-1A scout rifle. However; a Ruger Mini-14 in stainless steel would be a close second pick. All three of these rifles are more robust than an AR-15 but the Ruger can survive on minimal maintaince.

    1. avatar arc - the annoyance says:

      Indeed. I wrote it off as another wildcard cartridge but my next build, if I ever get the money for it, will be a 300AAC blackout. I’ll probably go through the trouble to get it suppressed.

    2. avatar Are you serious? says:

      The M1A and Mini-14 are more robust than an AR-15?… Hahahahahahahahahahahahahhahahahahahahahaha *breath* Hahahahahahahahahahahahahahahahaha

      1. avatar Elmer Fudd says:

        Are you kidding me?
        Direct impingement is more robust than Gas Piston?
        Aluminum receiver is more robust than steel or stainless steel? This is why the troops in Vietnam referred to the M-16 as the Mattel 16. The army was compelled to publish a propaganda comic book on how to clean and maintain the finicky rifle by referring to it as “the sweet sixteen.”. The implied sexual arrangement is considered statutory rape in most States.

        I understand that some AR-15 builders have seen the light and are now building variants with gas piston action.
        The only alleged advantage of direct blowback is a potential increase in accuracy. The motion of the gas piston presumably deflects the rifle from point of aim.
        News flash for you. By the time any action components begin moving any appreciable distance, the bullet has exited the muzzle.

        1. avatar Ropingdown says:

          It may be statutory rape in most states, unless….you are only 18 in Virginia, or only 26 in the New(som) California, and so on. Therefore in many locations it is convenient for young men to live very close to the border of a more flexible state. CA -their new rule makes no sense at all. Must be Hollywood lobbying that got the 10 years difference rule passed.

  10. avatar 300BlackoutFan says:

    Basically, 300 Blackout shines best with a ~8″ barrel and suppressor.

    Lightweight and maneuverable for home defense, with a round that generally won’t overpenetrate. Also, you don’t have to worry about permanent loss of hearing.

    Need 200 yards of knockdown power? Have a magazine or 3 loaded with supersonic ammunition.

    Deer hunting, but can’t use your 223 due to state laws? No worries, the 300Blackout achieves small/medium game kills relatively easily [with either subsonic or supersonic ammo]

    Reloading? I can reload 300 Blackout (subsonic) for about $0.15 per round.

    It’s not a perfect round to be sure – rather than doing one thing extremely well, it does a lot of things “well enough”.

    1. avatar Seans says:

      Not sure how you think 300BLK isn’t going to overpenetrate

      1. avatar Ropingdown says:

        If you refer to the supersonics for HD, sure they will overpenetrate. The 208, 210, and 220’s are for home/close defense. You well know, though, that the drive behind the creation of the .300 BLK was to provide a round that could be fired in a suppressed M4-rifle with only a barrel change, so with a 220 grain bullet. People keep talking about using a 9″ barrel suppressed, but 300 BLK suppressed is much quieter from a longer barrel, at least 14.5″, even better with a 16 or 18″ barrel. Granted, the shorties seem inherently cooler and more convenient given the extended length a suppressor adds. If quietness is the tactical goal though, long is better within reason.

  11. avatar john clark says:

    As I tell my Wife guns are like golf clubs, you need a big set to do different things and different jobs at different ranges!

    1. avatar Gun Nut at the Golf Club says:

      Good one…golf clubs. My long range golf club can only reach 250 yds. All around club 150yds.
      Normally I use shoes. Shoes for snow, hunting, running, office, reading, etc. all have different purposes.
      To the question, how many guns do you need?

      1. avatar arc - the annoyance says:

        Bare minimum? Three.
        An anti-tank rifle for anti-material work. (Probably stashed somewhere and only used in a team.)
        A good DM/battle rifle. (Bacon and eggs)
        A pistol. (In a tight area where rifle is too long, or broken weapon.)

        Some may include a shotgun, but I consider that to be a piece of utility equipment. Alternatively, replace the anti-material rifle with the DM rifle and have a SBR if you are in close and dirty.

      2. avatar Ropingdown says:

        “Less than I have and much less than I want.”

  12. avatar gus says:

    I read in an interview with the dude from AAC that, iirc, the there is very little difference between 300BLK and 300 Whisper, just enough to officially designate it as a different cartridge and get a SAAMI spec.

    functionally, the difference is that 300BLK is optimized for using both subsonic and supersonic loads, whereas 300 Whisper is not. I don’t recall the explanation for how that would be.

    the 300BLK comes into competition with the 5.56 because of those supersonic loadings. similarity to 7.62×39 was not the original intention, just a bonus.

    the 5.56 is still better for what it for what it does, flat shooting over a practical range, and even better for what it was originally intended for in the M16A1: a simple do-all rifle. point and shoot. no sight adjustment needed within 200 yards or a little at 300 yards.

    a reminder, though, you can’t just pop in a magazine and switch from subsomic to supersonic like that, or take on or off a suppressor. you have to have a variable gas system or change out the buffer. people forget that when claiming versatility.

    I think 300BLK is great. I would prefer it over 5.56. the only thing that keeps me from swapping calibers is the overwhelmingly plentiful supply and variety of 5.56.

    1. avatar 300BlackoutFan says:

      a reminder, though, you can’t just pop in a magazine and switch from subsomic to supersonic like that, or take on or off a suppressor. you have to have a variable gas system or change out the buffer. people forget that when claiming versatility.

      Hmm, I can do all 4 modes with 8″ Blackout AR-15, and I do not have an adjustable gas block, and I don’t swap out the buffer. Bolt-hold open on last round on all four modes. Do I get to claim versatility again?

      Also, wrt “variety” of 5.56 rounds – the 300 Blackout can use projectiles from ~100gr to 240gr. It can make use of the multitude of bullets (hunting and otherwise) used for .308. That’s quite a bit of variety….

      1. avatar gus says:

        yes, you get to claim versatility. in a short barrel. yep that’s where 300BLK is at its best. now try that in a 16″ barrel.

        SS109 (it is different)
        Mk 255 Mod 0
        Mk 262 Mod 0
        Mk 262 Mod 1
        Mk 311 Mod 0
        Mk 318 Mod 0
        Mk 318 Mod 1

        1. avatar Vic Nighthorse says:

          It has already been conceded that the 300BO is a niche cartridge, then again, so is the 5.56×45 even if it’s niche is arguably wider. A .338 Lapua fan boy could point out that your 5.56×45 is practically useless at and past 1000 yards too.

        2. avatar gus says:

          it is really good in short barrels, no doubt about that

        3. avatar CplCamelToe says:

          My 16” .300 BO works super/sub suppressed/loud with no adjustment, just like my 7” and 9”.

          Are you a special kind of stupid, or do you just like to say things about which you have no knowledge?

        4. avatar gus says:

          no I’m not a special kind of stupid, you’re just a special kind of asshole.

    2. avatar Seans says:

      300BLKs military requirements was to be able to switch between subs and supers and suppressed and unsuppressed with a non adjustable gas block.

      1. avatar Ropingdown says:

        Exactly. It shouldn’t require different buffer or spring. However, you need to have a correct choice of buffer to make them all work. Naturally. I switch uppers without a problem with my buffer…but the uppers are set for optimal gassing, it seems to me. A light buffer doesn’t do the job, but really isn’t optimal even for 5.56. JMO.

  13. avatar Vic Nighthorse says:

    The author here said that “the longer and heavier the bullet is, the tighter the twist rate needed to stabilize it.” My physics is weak but playing around with the Miller twist rate calculator it looks like bullets require less twist to stabilize as their mass increases, no? It is early for me so I could be confused I suppose.

    1. avatar gus says:

      more weight by itself, yes it takes a lower twist rate. but, for the same caliber, more weight means longer projectile, and that requires a tighter twist rate. projectile length has more of an effect than mass.

      1. avatar Elmer Fudd says:

        You should see the twist rate on the 16″ guns in Iowa class battleships. The twist rate works well enough for sub caliber, 4,000 fps projectiles out to 70,000 yards or more.

  14. avatar uncommon_sense says:

    I believe the author’s comparison is potentially unfair. If you must have a short (nine inches) barrel, then .300 BLK may be a better choice than 5.56x45mm NATO. If you allow for incredibly common 16-inch barrels, then I believe 5.56x45mm NATO is clearly superior — especially if you allow for soft-point bullets.

    An important fact to remember, you need velocity (perhaps greater than 2,000 f.p.s.) to penetrate common ballistic vests. A rifle with a nine inch barrel shooting .300 BLK will fall below that velocity quickly — within 100 yards — versus 5.56x45mm NATO which will stay above 2,000 f.p.s. at least to 400 yards.

    In the end it depends on what scenarios you expect to encounter.

  15. avatar gus says:

    as for M855A1 vs M193, no M855A1 is not better unless you are shooting at armored targets hundreds of yards away.

    within 100 yards, M855A1 ia overstabilized and the precessional wobble causes it to not penetrate as well as it could. M193, having more KE and not having the stabilization problem, penetrates better. and the rigid structure of M855A1 hinders its fragmentation.

    within 400-500 yards (I forgot exactly) the M855A1 loses its stability problem and will penetrate as well as M193, but the latter still has more KE and more likely to fragment.

    after that range, the M193 slows down and loses KE while the M855A1 does notm and penetrates better, also due to its rigid construction. at that point fragmentation is not its purpose.

    so M855A1 is better for cold-war style military engagements of armored targets at hundreds of yards. M193 is better for everything closer.

    why the Army sticks with it is beyond me, but they have done dumber things. after all there are other 5.56 variants that certain units can choose from instead.

    1. avatar Seans says:

      Where are you getting these numbers from? Cause none of them make sense.

        1. avatar Seans says:

          Yeah. That’s pretty much all wrong. M855A1 is vastly superior at all ranges than M193. It sounds like you are getting A1 confused with Greentip.

          M855A1 vastly outperforms M193 in terms of lethality. It reliably fragments down to 1900 FPS vs 2600 to 2700 for M193. It vastly out penetrates it. It’s yaw independent unlike M193. It’s barrier blind. The performance difference between the rounds is insane

        2. avatar gus says:

          checked it out. yep I was thinking of M855 green tip. M855A1 is definitely better.

    2. avatar Red in CO says:

      Uhh… I think you might be confusing M855 with M855A1. Those are two VASTLY different 5.56 loads

      1. avatar gus says:

        maybe so. I’ll take another look.

        1. avatar CplCamelToe says:

          So that answers that.

          You are BOTH a special kind of stupid, AND just like to say things about which you have no clue.

        2. avatar gus says:

          fuck off, asshole

  16. avatar Jim Carbonnow says:

    The author is as literally incompetent as the infamous Hoober

    1. avatar CplCamelToe says:

      Well, in fairness, Michael Arnold makes them both look like geniuses.

      Come on, Dan. Why do you let any retard with a keyboard write content for this blog now? You’ve turned this place into the Special Olympics of gun-writing.

      We’ve met, several times (both shows and writer events- we’ve ate, drank, and talked at length) and I genuinely like and respect you, but I’ve got to call a spade a spade: you’ve run this once-trusted blog into the ground by letting half-wits generate content.

  17. avatar Pete says:

    This misses the reason 300 BO was developed in the first place, it is designed to fit in a roughly MP5SD sized platform but have longer range than 9MM. This was to solve the issue of having a handy weapon for CQB that was less than optimal when forced to transition to intermediate distances, sy exiting a building and engaging a target a couple of hundred yards down the street. Oh and being suppressed was also a top design requirement so, subsonic loads.

  18. avatar EpsteinDidNOTKillHimself says:

    Yeah, uh, sounds all well and good.

    Fact is, I want a round that can do 90% of what I need it to do. From hunting varmints, to deer or even bear, to target shooting at longer ranges (500-1000yrds), to anti-material, to two legged varmints.
    And I need it reasonably priced and available (under non-COVID/election year) from the LGS, to the big box sporting goods store to even Wally-World (IF they even still carry ammo). Or for reloading, even cast.
    That last 10%, would be a specialty rifle or round, that would only see limited roles in use. Likely higher $$$$ in both the rifle, and the ammo. Likely a Safe Queen.
    I want that rifle I be willing to take out in the rain, snow, sleet, and not have to worry about squeeze trigger go click. Or that once in a life time 10 point buck.
    That 5.56 is not going to make that list.
    The 300BO . . . be more inclined to use it than the 5.56, but still too limited.
    Give me a .308WIN, 30-06, or half a dozen other common caliber rounds in a good rifle any day.

  19. avatar sound awake says:

    basic economics:
    5.56: 60 cents a round
    .300 blk: $1 a round
    7.62×39: 30 cents a round

  20. avatar BR says:

    Your velocity for 5.56 Mk262 out of 9” barrel seems way off. Out of a 16” barrel I’m getting about 2580fps for 75gr Hornady. I’m skeptical even with 5.56 pressures, you’re going to see 77gr getting 2573fps out of a 9” barrel. And if that number is wrong, your suppositions on energy are a lot further off as well.

  21. avatar busybeef says:

    5.56 when the barrel is longer than 12″
    300 BLK when the barrel is less than 12″ or suppressed.

  22. avatar Rifle Terminal Ballistics, explained says:

    Rifle bullets expand by collapsing on themselves due to high velocity (think driving a car into a brick wall at 100 mph). Pistol bullets are much slower (generally 1100 fps and under), therefore rely on hydrostatic pressure of the human body (mostly water) to fill a large hollow point cavity and cause expansion.

    Why is this important? Because when a rifle bullet slows down it becomes much less effective at expanding (think driving your car into a brick wall at 20 mph). Bullets cause damage by transferring energy–the larger the surface area of the bullet, the more energy it can transfer & hence why expansion is important. Despite what POTENTIAL energy the bullet has, it only matters what it can transfer. A rifle bullet going slow (under ~1800 fps is slow) is going to be significantly less effective. This means that after 150 yards, supersonic 300 BLK loses significant effectiveness, and subsonic is going so slow as to not expand at all (minus a couple specialty loads, which still have poor expansion compared to supersonic and are only good within ~80 yards). Otherwise, the slower bullet is going to punch a 30 cal hole through whatever is hit, but that provides limited trauma.

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