Muzzle Velocity Variations and Long-Range Shooting

A substandard rifle propellant can cause muzzle velocity variations.

And when this happens, most shooters struggle to make clean long range shots even with a good rifle and bullets.

You see,

Your rifle and ammunition must work in perfect harmony To hit your target over long distances.

The assumption is that when your rifle works perfectly, you shouldn’t have a problem achieving an excellent trajectory from the muzzle to your target.

Still, why do many shooters struggle with accuracy when shooting over long distances?

It all boils down to inconsistencies in muzzle velocity, shot after shot.

You can even miss your target beyond 700 meters using a rifle designed to deliver sub-MOA up to 300 meters.

The velocity variance can be significant as the bullet comes into contact with various atmospheric conditions at longer distances.

Even though several factors play a role in consistent velocities, this post will zero in on your propellant’s suitability and quality.

The article will focus on why it is essential to use a consistent and high quality rifle propellant.

The Effects of an Inadequate Propellant on Muzzle Velocity 

Let’s analyze how an inadequate propellant, (also known as the propellant load) can frustrate you when shooting at long ranges.

For starters, high quality ammunition and components for handloading will generate a standard deviation closer to zero.

Side Note: Standard variation is the number representing consistencies in muzzle velocities from one cartridge to another.

The common practice with many shooters is to take five to ten shots over a chronograph and then calculate the standard variation.

A variation close to zero indicates consistent average muscle velocities.

A bigger margin between the muzzle velocities after a string of shots indicates standard variation inconsistencies.

A high quality propellant designed for long range shots tends to deliver a stable burn rate resulting in a more consistent muzzle velocity standard deviation.

The Effects on Trajectory

Let’s move away from components and propellants and focus on a real world example to showcase the effects of inconsistent versus consistent velocity variation as the distance increases.

Study the table below;

Shooter	X	Y
Shot 1	2389fps	416fps
Shot 2	2415fps	2416fps
Shot 3	2424fps	2410fps
Shot 4	2406fps	2416fps
Shot 5	2406fps	2412fps
Muzzle Velocity (Average)	2408fps	2414fps
Standard Deviation	11.6	2

The data in this table was derived from two rifles loaded with .308 Winchester cartridges. The rifles use the same bullet, casing, and primers but different propellants.

Propellant X is popular with long range hunters. Propellant Y, on the other hand, is twice as expensive and sought after by long range precision rifle owners.

During this exercise, both rifles were loaded with the Hornady 168gr ELD match bullet. In addition, the guns can deliver sub-MOA groupings at 100 meters.

We will keep the propellant brands used in this experiment under wraps for now because the cheaper powder shooter X can deliver satisfying results for most hunters shooting within their long range abilities.

Still, as you can tell from the above results, shooter X recorded a more extreme spread between shots, reducing consistency.

What does this imply, and why is it crucial?

Let’s analyze the highest and lowest velocity differences for the two shooters above. 

Side Note: The following conclusions don’t account for the point of impact deviation caused by the rifle grouping capacity. Instead, it shows how a new trajectory develops as fresh muzzle velocities occur. 

Further, we’ll presume the target size for this experiment is 45cm by 45 cm. 

• 100 Meters: There won’t be an extreme spread at this distance. 

A ballistic calculator app indicates that at 100 meters, there won’t be a noticeable difference in bullet impact as a result of velocity inconsistencies for shooters X and Y.

• 300 Meters: The impact is still minimal with the shooter’s X bullet, resulting in a 2cm trajectory deviation between shots. There won’t be a visible effect for shooter Y.
• 500 Meters: The expected variation at this distance is about 8 cm for shooter X and 1cm for Y.
• 700 Meters: At this distance, the hit probability for a torso-sized target is difficult for shooter X as the standard deviation increases by up to 20cm between shots. Shooter Y is experiencing a deviation of about 1.7cm.
• 900 Meters: Shooter X can no longer achieve consistent engagements at 900 meters. At this range, the shooter is experiencing a super extreme spread of up to 40 cm between shots without accounting for the MOA grouping capacity of about 26cm. Shooter’s Y overall muzzle velocity at this distance is 3.5 max. 

Let’s break down the above example a little bit more.

Shooter’s X engages the target at 900 meters. Meanwhile, the bullet leaves the rifle’s barrel cruising at 2,389fps, landing 50cm from the initial point of aim.

As a result, the shooter adjusts his rifle’s turret and shifts his point of impact 50cm high. He then fires his second shot, this time generating a muzzle velocity of 2,424fps.

The bullet moves about 40cm high of the planned point of impact.

With such standard variations and inconsistent velocities, shooter X may continue to miss his target at longer distances.

The Bottom Line

If you’re a new long-range shooter or hunter, you may need help understanding the dynamics of average muzzle velocity.

However, the crucial point is that your muzzle velocities must be consistent or close between shots when shooting over longer distances.

Here’s what you should remember to help you achieve consistency between shots:

• Mind the quality of your propellant and rifle. High quality components include a tubular propellant and can deliver a consistent burn rate.

 Avoid using a powder dispenser to fill your rifle with gun powder to make it easy for you to generate consistent measurements.

• You must use high quality cartridges. Keep off cheaper brands to ensure consistent thickness from one cartridge to the next.
• Ensure your bullet’s quality is uniform from the base to the tip. That way, you can produce consistent internal pressure and cartridge lengths.

Happy long range shooting!