New bullet type?
Saw this post in today’s Shooting Wire and thought it was worth listing here. This is some really interesting stuff, and may even revolutionize ammunition.
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Bumpy Bullets Better?
In golf, dimples are the wings of a golf ball. It’s not the high coefficient of restitution that gives a ball it’s distance, although the compression (that’s COR) does help with the slingshotting effect off the club face.
Nope, it’s the dimples and their displacement of air that keeps the ball tracking further and straighter.
That’s why the number and pattern of dimples are a big deal on a golf ball. Most everything else is marketing, but the dimples really do make a difference in ball flight characteristics.
Technically speaking, it’s the result of relocating air and creating a turbulent boundary layer that moves the separation area (the area where the exterior surface of the ball no longer creates friction with the air molecules) further back on the surface.
The result is a thiner wake, making passage through the air easier.
It’s all about being more aerodynamic and less of a drag.
We’d heard the U.S. Army was looking into bullet technology with the goal of giving snipers a flatter shooting bullet that was more, well, slippery. Apparently, U.S. Army officials at the Aberdeen Proving Ground have moved bullet technology forward – using some of the principles used in golf-ball technology.
Bullets, if you look at them, have not truly been created for optimal aerodynamic characteristics. The nose of the bullet has changed, but not a lot has happened beyond the nose.
That’s the equivalent of making an aerodynamic bumper, but putting the same old square truck behind it.
The Army is now testing changes beyond the nose, evaluating a dimpled bullet that has reportedly reduced projectile drag, yielded a flatter long-range trajectory with much more retained energy at the target.
Their search for “slippery” may have actually yielded the next big break in bullets.
After testing circumferential drive bands, dual-radius ogives, and rebated boat-tails, the dimpled bullet was given a try.
It was the long shot of the group (ouch) – but it absolutely no one expected the performance it has delivered.
Nominal drag coefficients (Cd) have improved- markedly- and muzzle velocities have jumped +80fps in .308 test guns.
Terminal performances have been described as “spectacular” giving snipers a more slippery bullet with enhanced long range performance and way-better results on “soft targets”.
In short, the Army’s already a potent snipers have been given a better-killing bullet. So much better that some of the dimples in the ongoing tests have come from the smiles on the faces of the testers.
The design for the new dimpled round is reportedly a copper-jacketed bullet with dimples about 0.5mm in diameter. Early tester rounds were produced in binary impact swages that press-formed the dimples after the bullets came from conventional dies.
Next-gen bullets will be made using an advanced metal-injection-molding (MIM) process, putting the dimples directly on the surface of the bullet’s jacket. That new high-tech jacket is being called a MIM Exo-Jacket (as in exoskeleton).
The core’s composition remains classified.
With lowered drag the dimpled bullets exit barrels faster (due to reduced surface friction). And while the .308’s +80fps in added performance is exciting, the higher-pressured .338 is picking up nearly 150fps. That’s somewhere impressive and rapidly-approaching awesome. And it’s with identical powder charges and cases-the only changes were the dimpled bullets themselves.
And then there’s the unexpected bonus.
While full-metal-jacketed bullets break along the cannelure – that band around the cylindrical part of the bullet and fragment, the thinner and more irregular walls of the dimpled bullet have multiple fragmentation points.
Instead of breaking up, the bullet effectively blows up in soft targets. Longer distances, flatter trajectories, increased velocities, and enhanced performance on “soft targets” – sounds like a winner to me.
I always knew whacking hundreds of thousands of golf balls would eventually do me some good. Just never thought they’d be the basis for understanding how engineers were improving bullet performance.
–Jim Shepherd
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