Videos Reveal Rifle Movement Before Bullets Exit Bore of Barrel
This report is from Bryan Litz and the ScienceofAccuracy.com website.
As long as there have been rifles, there has been a debate as to how much – if any – the rifle moves prior to the bullet exiting the bore. The first video below shows a Barrett MRAD chambered in .338 Lapua Magnum firing a 300gr Lapua Scenar bullet. Capturing projectiles at 100k+ frames per second allows us to visualize aspects of the firing sequence that are otherwise invisible to the human eye.
Click Video to see barrel with suppressor (on right) move with recoil before bullet exits.
What is clear from this video is that the rifle system is moving rearward while the bullet is traveling through barrel and subsequently through the suppressor. During the “in-bore” portion of bullet travel, any deviation of the muzzle orientation from the initial point of aim can cause a point of impact change. This is because the bullet will exit while the barrel is pointed somewhere different than when the shot was initially fired. Much of the shot’s point-of-aim orientation can be maintained through consistent marksmanship fundamentals and recoil management techniques. However, most shooters are not likely capable of managing it to less than 0.001″ for EVERY shot, especially given on lightweight magnum rifles.
Here’s another example with a 180gr bullet in a Rem 700 BDL .30-06 rifle. “Every time we watch a video like this it reminds us that guns like this, the majority of accuracy and precision come from the gun/sight/support system, not the ammo. When you consider that 0.005″ of muzzle deflection, (orthogonal to the bore) results in ~1.5 moa of dispersion (.75 in any direction) and you see this massive barrel movement prior to bullet exit, it’s clear that the vast majority of dispersion [for typical rifles] is coming from this movement”.
Precision rifle systems, such as benchrest, PRS, and F-Class rifles, tend to minimize the movement away from the bore axis prior to bullet exit to achieve the best possible precision. A common theme among the most precision systems is higher-weight rifles with lower-weight projectiles. This relates to basic physics: Newton’s Third of Motion “For every action, there is an equal and opposite reaction.” With all else held equal, if the rifle weighs more and the bullet weighs less, there is a lower magnitude of motion prior to the bullet leaving the barrel.
In our latest book, Modern Advancements in Long Range Shooting Volume III, Chapter 3 covers the Theory of Precision for Rifles which mathematically describes and estimates the precision potential of rifles based on rifle mass and kinetic energy of the bullet. The chapter includes all the live fire test data to support the theory and great discussion on the testing performed can be found on our podcast at the Science of Accuracy Academy website.
Get the Book: Modern Advancements in Long Range Shooting III
Listen to the Podcast: Science of Accuracy Podcast
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