Grain Weight Considerations
Table of Contents
Hey all, we here at True Shot Academy are going to go over the concept of grain weight today. Grain weight is something one will encounter with most, if not all metallic cartridges on the market. Our goal with this blog post is to provide a brief overview of grain weight, what it is, how it matters, and more. Without further ado, let’s get into it.
What is Grain Weight?
In the realm of firearms, the term “grain weight” refers to the weight of a projectile. Projectiles are measured in grains, a unit of measure which equates to about 65 milligrams (0.065 gram). The term has been applied to bullet weights as it was a common and uniform unit of measure used by apothecaries. In the context of firearms, it was used to refer to the amount of lead necessary to form cast lead bullets.
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What Influences Grain Weight?
Grain weight is influenced by the mass of the projectile itself. The use of more material equates to greater mass and a heavier weight. If a loading is of the hollow point or open tip match (OTM) variety, the projectile will shed weight due to less material being used overall. Simply put, if material is removed to facilitate a hollow point or OTM loading, the projectile will be lighter than a full
The specific material used will also have an impact on the grain weight of a loading. This becomes especially evident if you compare two popular types of
5.56x45mm NATO ammo offerings, M1913 and M855 green tip loadings. M193 loadings feature a lead core full metal jacket (FMJ) projectile which weighs in at 55 grains. Conversely, an M855 loading will feature an FMJ projectile with a steel penetrator which weighs in at 62 grains. The introduction of steel into the equation led to the M855 loading outweighing the all lead M193 loading. Other materials such as copper for specialty loadings and amalgamations of alloy used for frangible also influence grain weight.
Some Firearms Prefer Specific Grain Weights
Some firearms have a clear preference when it comes to grain weights and types of loadings. This factor is mainly associated with autoloading firearms as manual action firearms are not dependent upon the inertia of the round to function. Depending on the specific type of firearm or how it is configured, a shooter may find that their firearm prefers one grain weight over another. For example, some blowback operated PCCs can be picky with
ammunition, often requiring 124 grain
9mm Luger loadings for optimal function.
Simply put, loadings generate inertia when fired and can sometimes be too anemic or too much for specific firearm. Too little inertia can lead to malfunctions while loadings which are too hot or generate too much inertia can potentially lead to damage. The wide range of
ammunition will allow an end user to find a loading and grain weight optimal for their use cases and reliable function of their firearm. This ultimately ties into the relationship grain weight has with the overall velocity of a loading.
Relationship with Velocity
The grain weight of a projectile has a direct relationship with velocity. In addition to the powder charge of a loading, the projectile of a cartridge influences the potential velocity one can achieve. Lighter projectiles are capable of higher velocities due to their lightweight nature. Conversely, heavier projectiles are going to travel slower than their lighter counterparts due to their additional weight. As mentioned above, this velocity contributes to the overall impulse and inertia of a loading. This can lead to either reliable function of a firearm or hang ups with certain firearms and operating systems.
Impact on Performance
A projectile’s grain weight can also influence its performance when fired downrange. As mentioned above, lighter projectiles are more conducive to higher velocities while heavier projectiles lead to slower velocities. This factor can become important when developing loadings for specific use cases.
Subsonic
ammunition intended for suppressed use will generally feature heavier projectiles. These projectiles keep velocities lower and aid in ensuring that the rounds do not go supersonic. Many match grade and precision loadings will generally feature heavier projectiles to ensure that the round is not disrupted as much by wind in flight. To make up for potential velocity losses, some manufacturers remove material from projectiles and utilize either polymer tips or hollow point or OTM type bullets. By removing material and lightening the projectile slightly, a loading’s velocity potential increases. This is why some heavier loadings such as 77 grain OTM
5.56 ammo offerings and 175 grain
.308 Winchester OTM loadings are commonly used for long range shooting.
Defensive
ammunition can be found in both light and heavy grain weight offerings. These various options allow manufacturers to produce
ammunition in various calibers suitable for a wide range of firearms. Specifically, lighter hollow point loadings are optimal for self defense as they are generally capable of achieving the desired amount of penetration on target while also facilitating expansion on impact. A fast-moving projectile which suddenly stops and expands is highly effective for self-defense.
Recoil Considerations
Generally speaking, heavier grain weight loadings with lower velocities tend to have less recoil than their lighter, faster counterparts. Granted, one will be feeling a brunt of the recoil when using a manual action firearm whereas autoloading firearms tend to soak up recoil impulse during their operation. Since heavier grain weights lead to slower projectiles, less impulse is being generated. This typically translates to more of a rearward push towards the shooter rather than a snappy, vertical biased recoil impulse common with higher velocity loadings. Some heavier firearms or well-tuned autoloaders may even shoot so smoothly with certain calibers and a variety of grain weights, making it hard for some shooters to tell the difference.
Relationship with Twist Rates
Barrel twist rates are optimal for specific ranges of bullet weights. Faster twist rates, such as 1:7 twist rates, are well-suited for stabilizing heavier projectiles. Slower twist rates, such as 1:9 twist rates, are optimal for stabilizing lighter weight projectiles. It is also worth noting that if a specific loading is optimal for a specific twist rate, it can also be effectively used in faster twist rate barrels. For example, a loading optimized for a 1:9 twist rate will also perform well in faster 1:8 and 1:7 twist rate barrels. If one wishes to make the most out of their shooting experience, they will seek out a loading with a grain weight appropriate for their twist rate.
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How Important is Grain Weight Really?
At the end of the day, for recreational plinking, determining an optimal grain weight is certainly not a matter of life and death. For this use case, one can simply seek out the cheapest and best quality
ammunition they can find to get the best bang for their buck. For other use cases and specialized shooting activities, grain weight becomes more important and worth looking into.
Conclusion
All in all, bullet grain weight is an important factor to be aware of as a shooter. Whether you are getting into the weeds and selecting an optimal loading for your use cases and firearms or simply want to find something you like, being knowledgeable about grain weights is certainly important. We here at True Shot Ammo have a wide range of
ammunition for sale, encompassing many calibers and grain weights. Whether you want to
buy ammo for hunting, plinking, suppressed use, self-defense, or another purpose, we here at True Shot Ammo have got you covered. As always, happy shooting.
Need bulk ammo? At True Shot Ammo, we have a wide variety of handgun ammo and rifle ammo available to purchase. Please visit our website trueshotammo.com, call us at (888) 736-6587, or you can email us at sales@trueshotammo.com for more ammo options.
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