Primary Arms Staff

7/6/2020 1:22 pmwww.primaryarms.com

When shopping for a tactical rifle or carbine, you have a wide variety of calibers to choose from. Each caliber has its own benefits, which are optimized for a specific purpose. Some calibers are tailored towards close-quarters combat, while others sacrifice mobility for precision at distance.


In this blog, we’re taking a closer look at the most common ‘tactical’ rifle cartridges in America. This includes both intermediate and full-power rifle cartridges, along with a handful of magnum and super-magnum cartridges for long-range or anti-material roles. In each section, we’ll describe the cartridge’s major benefits and key considerations for achieving peak performance.



Before we get into individual calibers, let’s take a look at the key components of a cartridge.


Cartridge Anatomy


Rifle Cartridges are made of several different components, each of which contributes to the overall performance.


Bullet: Cartridges are not the same as bullets, though the bullet is a critical component of any cartridge’s performance. Bullets are usually described by their weight (in grains), caliber (diameter in inches), and design properties. Such properties include:


Full Metal Jacket: This is the ‘standard’ for most range ammunition. FMJ describes a simple copper jacket around a bullet, excluding its base.


Total Metal Jacket: TMJ bullets have a jacket that covers the entire surface, including the base. TMJ bullets are often more accurate than standard FMJ, but they usually cost a little bit more. Some ranges might require the use of TMJ to limit lead exposure.



Solid Copper: Solid Copper bullets are one piece of solid copper. Unlike FMJ or TMJ, there is no soft lead core at the center. The result is a very lightweight bullet with good penetrative properties. Solid copper rarely expands or fragments on impact, so we recommend against it in tactical applications.


Hollow Point: Hollow Point bullets have a hollow tip that aids in expansion on impact. Expansion reduces overall penetration, which is a desirable feature for self-defense ammunition in close quarters.


Soft Point: Soft Point bullets have an exposed lead tip, which collapses on impact and recreates the effect of a hollow point. These are beneficial for rifles that cannot reliably cycle hollow point ammunition.


Ballistic Tip: Ballistic Tip bullets are a modern design that caps a hollow point round with a polymer tip. This tip improves the aerodynamic properties of the bullet and increases its ballistic coefficient. The tip also assists in expansion, as it is forced into the body of the bullet on impact. Due to the higher price, this ammunition is commonly reserved for hunting and long-distance competition, though it can perform well in a tactical setting.



Boat Tail: Some bullets feature a Boat Tail design, which indicates a concave dip in the base of the bullet. Boat Tail bullets have a few notable benefits, including a slightly higher muzzle velocity and improved aerodynamics. Boat tail ammunition is usually more expensive than the flat-base alternative.


Armor Penetrating/Penetrator: Some ammunition is considered ‘armor penetrating’ by having a reinforced core or ‘penetrator’ tip—such as M855 ‘Green Tip’ 5.56 ammunition. Penetrator ammunition fares well against barriers and rifle armor, but it can come at the cost of reliable expansion. New penetrative ammunition like M855A1 strikes a good balance in performance on both soft and hard targets.


Tracers: Though tracer ammunition is available for civilian purchase, its benefits are ill-suited for most civilian use. Tracers have a mild incendiary property that helps indicate trajectory and point of impact. Tracers are used primarily for machine guns, as it guides both the gunner and his team when engaging distant targets.


Casings: Bullets are seated in a casing, which contains the propellant and a primer. Case dimensions determine the velocity and pressure of a cartridge, as larger cases can contain more powder at a safe pressure. Case dimensions also impact reliability in semi-automatic firearms, as it determines the size and shape of a rifle’s chamber and magazines.



When comparing case materials, annealed brass is the top choice for reliability and consistency. Steel is more affordable, but some rifles cannot reliably extract steel ammo, leading to more stoppages and malfunctions. Even so, steel cased ammunition is perfectly acceptable in the right rifle, such as an AK chambered in 7.62x39.


Primers: The primer is your ignition device, set in the rear of the cartridge case. When struck by a firing pin, the chemicals in the primer detonate and ignite the propellant powder, which causes the bullet to accelerate down the barrel.


When choosing defensive ammunition, primer consistency is an important consideration, as bad primers will cause immediate stoppages.



Powder: Powder choice varies from caliber to caliber, as every cartridge has an optimal burn rate. One of the most important aspects of quality ammunition is powder weight consistency. Your shots will be more accurate if every cartridge has the same amount of powder. Cheap ammunition may have larger variances in powder, which can cause irregularities in velocity.


For reloaders, powders are an important consideration during load development. No one chooses the right option on a guess. It takes relentless experimentation to determine what powder and throw weight will work best with your rifle and bullet selection.


Now that you’re familiarized with the basics of rifle ammunition, let’s take a look at some of America’s most popular tactical rifle calibers, starting with 5.56x45 NATO.


5.56x45 NATO/.223 Remington



The US Standard for Tactical Rifle Cartridges.


5.56x45 (and its little brother, .223 Remington) are the most popular choice for tactical carbines in the United States. 5.56 is a versatile, low-impulse intermediate caliber that has served with the US Military since the Vietnam Era. As a result, its past is littered with public debates surrounding ‘stopping power’, but terminal ballistics research has proven its effectiveness. Like every cartridge, 5.56 has a sweet spot, and its performance relies on proper application in a suitable environment.


In general, 5.56 bullets weigh between 50gr to 80gr and will travel from 2400-3400fps, depending on barrel length. The terminal ballistics of 5.56 can vary greatly from load to load, as the .22-caliber bullet will underperform if pushed outside its ideal velocity. Fragmentation and expansion are particularly important for a reliable wound channel, so ammunition selection is critical when using 5.56 for personal defense. In the United States, 5.56 ammunition is among the most affordable and easily-accessed, but its popularity can cause scarcity during market panics.



Note, though .223 is often used synonymously with 5.56x45, buyers should recognize a subtle difference. While .223 can always be shot in a 5.56-marked rifle, 5.56 may damage some .223-marked rifles. This is not just because 5.56x45 is usually a slightly higher pressure than .223 Remington. Because 5.56 rifles are built to a military spec, they're made to accommodate longer tracer bullets. As a result, there's more space set between the bullet and rifling when chambered. However, if a 5.56 cartridge is put in a .223 rifle, it may set the bullet against the rifling, which can cause a pressure spike with catastrophic damage. 


.300 AAC Blackout



Superior Choice in Suppression and Short Barrels.


.300 AAC Blackout (or .300BLK) is an intermediate caliber developed by Advanced Armament Corporation, combining the versatility of .30-caliber bullets with the ubiquity of AR15 parts and accessories. From the onset, AAC designed .300BLK to maximize compatibility with 5.56 AR15 components, including compatibility with bolts and magazines. This made .300BLK a favorite among both military and civilian customers.


.300BLK has a unique ballistic profile, which is often compared to 7.62x39. One defining feature of .300BLK is its wide variance in bullet weights, which range from under 100gr to over 220gr. As a result, it can be difficult to pin .300BLK to a specific velocity range, though most users will divide .300BLK ammunition into two categories: supersonic and subsonic.



.300BLK shines most when paired with suppressors and short barrels. The powder used in .300BLK cartridges burns quickly, so short barrels are more efficient on .300BLK than 5.56. Combined with a suppressor and subsonic ammunition, .300BLK is an exceptional performer in close quarters, making it a top choice for any personal defense weapon.


7.62x39 and 5.45x39



The Most-Proven Combat Cartridges in the World


With no exaggeration, these two Soviet-designed calibers have proven their merit in every climate and every condition on the planet. While 7.62x39 and 5.45x39 are very different in performance, they share a common bond through the AK platform, which is why they are so frequently compared.


7.62x39mm is a heavy-hitting intermediate cartridge, firing a 122gr to 154gr bullet between 2100-2400fps. Due to its steep trajectory, 7.62x39 is best used within 400 yards, though the heavy bullet can still pack a punch at further distances. This cartridge was in-service with the Soviet Military since the mid-1940s, and its effectiveness in combat is bordering legendary. The AKM is probably the most prolific assault rifle in the world, and its prominence has given 7.62x39 a global userbase. As a result, many Americans choose 7.62x39 for their primary tactical rifle.



5.45x39 is a later addition to the Soviet arsenal, introduced in the mid-1970s with the AK74. This cartridge has many similarities to 5.56x45mm, but there are several noteworthy differences. 5.45 cartridges feature a longer bullet with a shorter case length, which translates to slightly slower muzzle velocity and a slightly higher ballistic coefficient. Of course, with the diverse selection of ammo for both 5.56 and 5.45, debating a general comparison is unproductive. On its own, 5.45 is a compelling lightweight cartridge that offers volume of fire and great terminal ballistics from close to medium range. Outside 500 yards, both 5.45 and 5.56 struggle to keep up with larger cartridges—such as the next item on our list.


6.5 Grendel



The Hybrid of Intermediate and Full-Power Rifle Cartridges


Designed in 2003, 6.5 Grendel is a powerful intermediate cartridge that extends the range of the AR15 to 800 yards and beyond. From a ballistic perspective, 6.5 Grendel is a middle ground between 5.56 and .308, offering a greater effective range with minimal added weight. 6.5 Grendel is also compatible with most standard AR15 components, though it requires a dedicated bolt and magazines for reliable function.


Most 6.5 Grendel bullets weigh between 90gr and 130gr, traveling between 2500-2900fps from muzzle. With the right bullet and barrel, 6.5 Grendel users can easily engage targets out to 1000 yards. Few other AR15-compatible cartridges are capable at that distance, making 6.5 Grendel a top choice for users looking for a strong general-purpose round that can reach targets at long range.



Of course, if long-range is your primary focus, the next caliber can reach even further…


.224 Valkyrie



Long-Range Precision for the AR15


.224 Valkyrie is a relatively young cartridge, designed as recently as 2017 by Federal Ammunition. Like 6.5 Grendel, this cartridge seeks to increase the range potential in the AR15 footprint. In this regard, Valkyrie is an undeniable stand-out performer.


.224 Valkyrie cartridges feature bullets between 60gr to 90gr, with average velocities ranging between 2600fps and 3400fps depending on barrel length. Most .224 Valkyrie bullets feature an extraordinarily high ballistic coefficient, indicating their aerodynamic properties and potential for long range precision. Compared to 6.5 Grendel, .224 Valkyrie stays supersonic to further distances, making it superior at extreme ranges, though Grendel will hit with more energy.



Honorable Mention: Pistol Calibers (9mm, .40 S&W, .45ACP, 10mm, 5.7x28)


Unmatched Agility for Close-Quarters


Pistol-caliber carbines draw from many of the same benefits as submachine guns, making them a top choice for personal defense in close quarters environments. With minimal recoil, reduced weight, and a wide variety of ammunition, PCCs earn pistol cartridges an honorary spot our guide to tactical rifle calibers.


This category includes cartridges like 9mm, 10mm, .45ACP, and FN’s 5.7x28. Though pistol cartridges lack the power of their rifle counterparts, these calibers can be used with minimal barrel length in featherweight carbines for unmatched agility.



Paired with modern hollow point ammunition, a PCC can be a capable option for personal defense, allowing for rapid-fire close-quarters accuracy that cannot be easily matched by intermediate calibers.


.308 Winchester/7.62x51 NATO



America’s Most Popular Full-Power Rifle Cartridge


.308 Winchester (and its little brother, 7.62x51mm NATO) have been a mainstay in American arsenals for over half a century. Originally designed as a part of the Military’s T65 experimental cartridges, .308 is a civilian equivalent to the later-released 7.62x51. The relationship is similar to .223 and 5.56, but in this case, the civilian .308 is higher pressure than 7.62x51. Even though 7.62x51 is the official military cartridge, most modern battle rifles are built around .308, since .308 rifles can fire both .308 and 7.62x51 without damage from excessive pressure.


Most experts would describe .308 as a strong general-purpose rifle cartridge. With an effective range that reaches past 700 yards, .308 delivers a 125-185gr bullet at muzzle speeds between 2500fps and 3100fps.



With wide support through the industry, .308 is a capable cartridge at any distance. Even in close quarters, .308 can perform well when paired with a lightweight battle rifle like the SCAR 17. Though it will never be as agile as 5.56, .308 can hit harder at much greater distances, which is why many Americans choose .308 for their primary defensive cartridge.


6.5 Creedmoor



The Leading Precision Rifle Cartridge


Introduced in 2007 by Creedmoor Sports and Hornady Ammunition, 6.5 Creedmoor excels in long-range precision. Since its release, 6.5 Creedmoor has won the favor of marksmen worldwide, now finding use within elements of SOCOM. Though it was designed for target shooting, its ballistic properties are eye-catching on any tactical team.


6.5 Creedmoor cartridges fire a 120g to 143gr bullet at speeds ranging from 2700-3000fps. Leveraging the high sectional density of 6.5mm bullets, 6.5 Creedmoor achieves ballistic coefficient values far above most .308 loadings.



Combined with its flat trajectory, reduced recoil, and strong terminal ballistics, 6.5 Creedmoor is building a reputation as a replacement for .308. Aside from ammo cost and barrel life, 6.5 Creedmoor outperforms .308 in almost every major category, though .308’s tradition and lasting popularity will keep the debate alive for decades to come.


.300 Winchester Magnum



Proven Long-Action Effectiveness


Moving into long-action cartridges, .300 Winchester Magnum is a trusted favorite for long-range precision. As with most magnum rifle cartridges, .300 Win Mag favors bolt action rifles, though semi-automatic options exist at a higher cost.


.300 Winchester Magnum is a highly versatile cartridge, finding widespread use with hunters, competitors, law enforcement, and military alike. With a 165gr-220gr projectile, .300 Win Mag’s muzzle velocities average from 2800-3300fps. Compared to other rifle cartridges on this list, .300 Winchester Magnum packs a punch, which gives it a maximum range far beyond the 1000-yard line.



For personal defense, .300 Win Mag is usually a poor choice, though it’s a great option to have around for hunting and long-distance practice. Still, some would say it’s a lot more reasonable than the next item on our list.


.338 Lapua Magnum



Powerful Magnum Cartridge for the 1-Mile Target


While it technically qualifies as a ‘tactical’ rifle cartridge, .338 Lapua Magnum is optimized for a very specific role with military snipers. Capable of penetrating armor plates at over a kilometer away, .338 Lapua Magnum hits harder than any other cartridge on this list, as it pushes a 225gr-300gr projectile at velocities ranging from 2800-3400fps.


As with .300 Win Mag, bolt-action rifles are the top choice for .338 Lapua. Although semi-automatic options exist, this cartridge demands exceptional precision in its ideal distances, where rushed follow-up shots are rare.



.338 Lapua Magnum also carries a reputation for its price. As with similar super-magnum cartridges, .338 Lapua encourages handloading, since factory ammunition can cost $6 per round. This is largely due to the high quality Lapua brass, which costs $2.50-$3 on its own. With recycled brass, hand-loading reduces the price to just over $1 per shot, and the resulting cartridge is usually more accurate too. As an investment, a $600 reloading set pays for itself in roughly 120 rounds of .338 Lapua.


Conclusion


Each caliber on this list is optimized for a slightly different task. Even cartridges as similar as 5.56x45 and 5.45x39 are divergent enough to be considered for their own unique benefits. By understanding each cartridge’s design, you can ensure that you choose the right firearm for any scenario.


If you’re interested in building or buying a rifle in one of these calibers and need additional information, feel free to reach out to us on social media, including Facebook, Twitter, and Instagram. We’re more than happy to help you get a setup that can meet any budget or preference.