Can you fire 556 AMO in a 300 black out rifle?

Can you fire 556 AMO in a 300 black out rifle?

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  1. In some instances, the 5.56x45mm NATO cartridge might chamber in a 300 Blackout rifle, and even fire. But such use is to be highly discouraged .
    Not only might the 5.56 case become stuck in the chamber, but the 5.56 cartridge is loaded to a higher max pressure (62,350 psi vs. 55,500 psi). It’s quite likely the 5.56 cartridge will balloon it’s neck out to .30 caliber against the leade of the barrel’s rifling causing it to lodge in the chamber.

    Can you fire 556 AMO in a 300 black out rifle?

    5.56x45mm NATO (L) versus the 300 Blackout (R)
    The bolt may have to be “assisted” to full closure before firing too. If so, a case neck rupture or stuck case is highly likely to occur. Since the 5.56mm bullet is .224″ in diameter it will not seal the bore of the gun when fired. The result will be very poor performance (lower velocity and accuracy) because the bullet will go bouncing down the barrel like a BB through a large straw and it will lack stabilized spin from the rifling too.
    NOTE: Due to the possibility of mixing the wrong ammunition or magazines in the AR platforms, some companies offer ways to identify the intended use of your magazines. Colored floorplates, magazines and even ID bands can be used to alert the user.

    Can you fire 556 AMO in a 300 black out rifle?

    The Danger of a 300 Blackout in a 5.56mm rifle
    The 300 Blackout may chamber and fire in a 5.56mm rifle, usually with disastrous results.

    Can you fire 556 AMO in a 300 black out rifle?

    This occurs because of the dimensions of the 300 Blackout cartridge which was based on the shorter .221 Fireball cartridge (which was a shorter version of the .222 Remington).
    In a normal .223/5.56 chamber, the cartridge headspaces on the shoulder of the cartridge case, as show in the cutaway view below.

    Can you fire 556 AMO in a 300 black out rifle?

    If you introduce a 300 Blackout into the chamber of a .223/5.56 rifle an artificial headspace condition can occur that allows the bolt to close on the cartridge. See the next cutaway view below.

    Can you fire 556 AMO in a 300 black out rifle?

    As you can see, the bullet is larger than the bore opening and when fired, the edges of the chamber will act like a swage to compress the bullet. But it will also mean very high chamber pressures, which can rupture the firearm itself. Even if things go reasonably well and the bullet is pushed into the bore, it’s likely to become lodged there, blocking the increasing pressure. Something is going to fail.

    Can you fire 556 AMO in a 300 black out rifle?

    300 Blackout bullet lodged inside a 5.56mm test barrel. That long, skinny gray thing in the middle of the cutaway view is the .30 caliber bullet.

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  2. It’s fairly obvious that using the correct ammo for a specific firearm is an absolute must. In some ways, 5.56 ammo can chamber in a 300 blackout rifle, but it’s absolutely not recommended. To avoid destroying and damaging your firearm, you should have strong attention to detail, especially when talking about weapons.

    Can you fire 556 AMO in a 300 black out rifle?

    When discussing which one is best: 300 Blackout or 5.56 ammo, I should say that both of these rounds are pretty similar and are designed to use the same or similar type of rifle. But it doesn’t mean that they have the same ballistic performance.
    If you’d like to ammo, I recommend checking out Bulkmunitions. They’re experienced professionals who sell the cheapest ammo in bulks.
    Recently, news about firearms consistently mentions weapons chambered for the new 300 AAC Blackout cartridge. It increasingly attracts the attention of special forces army units and police in many Western countries, including the United States. Cartridge .300 AAC Blackout is equipped with bullets weighing 7.13 to 15.55 grams. Heavy bullets weighing 14.26, 15.55, 13.48, or 12.96 grams from different manufacturers reach muzzle velocity from 281 to 317 m/s and muzzle energy from 560 to 761 Joules. The price of the 300 Blackout is twice the price of 5.56. 300 Blackout has better energy and penetration and works better at close range. However, it can cause over penetration, so it’s not the best choice for home defense.
    5.56 is milder and has a good ballistic performance. It’s also better for home defense because 5.56 was designed to fragment on impact to prevent over-penetration. It’s used for firing in various climatic conditions at temperatures from – 50 ° C to + 50 ° C. Adopted by NATO countries in the 1980s. 300 Blackout has better energy and penetration and works better at close range. However, it can cause over penetration, so it’s not the best choice for home defense.
    If you’re interested in which one is better, the answer is easy! Use 300 Blackout while hunting or when you want to neutralize a bigger threat and for home defense, use 5.56.

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  3. In an unmodified 300blk rifle? I hope not. The out of battery safety should prevent the weapon from firing because the length of the 556, relative to the 300blk, would prevent the bolt from closing.
    Now, if you had a spare barrel for your 300blk rifle that was chambered for 556, sure: My (hypothetical) 300blk Thompson Contender chambered in 300blk could easily handle 556 with nothing more than a quick barrel swap.

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  4. No. Fire 5.56 ammo only out of rifles chambered for them and shoot only 300 Blackout out of rifles chambered for that cartridge.
    ATTENTION NEW SHOOTERS
    Until Further notice, please shoot only the caliber cartridge marked on your firearm. Once you successfully fire the ammo approved for your firearm then, and only then, please feel free to consider shooting alternative cartridges. You will get a lot of mileage out of your local gunsmith.

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  5. You can fire a .300 BLK in 5.56mm NATO.
    Accuracy will be terrible. Muzzle flash will be enormous. You probably will not hurt the rifle.
    I do not recommend it.

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  6. I figure one of the good readers here will go home and check, BUT I don’t believe your setup will function a 5.56 round successfully. I believe the 5.56 would successfully strip from the magazine and go into the chamber just fine. What I believe would happen is that the 5.56 would fall further into the chamber than the .300 round as the .300 chamber doesn’t have the features that a 5.56 needs to chamber against.
    On the other hand, I know several people have successfully (and painfully) chambered and fired a .300 Blackout in a 5.56 chambered gun. I don’t know if all 5.56 barrels will chamber a .300 (I tried one of mine, and it did NOT), but evidently some will.
    IF the 5.56 round chambers up properly, and the gun is able to go into battery, then I’m assuming the round would fire just fine. What would happen after that? Eh, the .223 is going to bounce down the barrel, you’ll get some fire blow by the round, and if you can build up enough gas pressure at the port, the action will cycle. Is the gun going to explode? Probably not . . . don’t really see how. The .223 isn’t going to be able to build up pressure as much because there’s no bullet to barrel seal. The breech is, essentially, locked, and once in that position, the action is agnostic to a .300 or 5.56. It’s got a perfectly fine rear end of the round that it’s designed to hold.
    Is the barrel going to be damaged? Probably not . . . not from 1 or 2 rounds, at least. It’s a soft bullet going down a hard barrel.
    Now, reverse that loading and put a .300 in a 5.56, it’s a bit different story. 🙂
    And, no, I don’t recommend trying either. I’m speculating. BUT, I’ll bet there’s a video on youtube of someone doing it. 😀

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