Bumpy Bullets Better?
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Old 03-19-2010, 04:13 PM   #1
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Default Bumpy Bullets Better?

From The Shooting Wire for Friday, March 19

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.

On another note, the feedback from last week's three-part feature on "mouse guns and penlights" has apparently struck a note with readers - and manufacturers.

We've heard from many of you wanting to know the best loads for the small guns, and we're working on that. We have also been told by "highly placed sources" that there will be even more "mouse gun" news at the NRA Annual Convention in May.

Don't have many details - yet- but it's safe to say there will be even more mini-and micro- concealed carry selections to choose from.

Finally, we have confirmed several of the big distributors are finally getting popular caliber ammunition back in stock.

We're also hearing that prices are also starting to fall a bit. Not to price points before the "Obama bounce" last year, but certainly enough that many price-conscious shooters may actually start thinking about heading back to the range.

We'll keep you posted.

--Jim Shepherd

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Old 03-19-2010, 04:15 PM   #2
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Oh I hope they call them ruff riders...

Great post cane.

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Old 03-20-2010, 03:09 AM   #3
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Default Dimpled Bullets

Oh great, now I'll have to worry about my rounds slicing into the rough.

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Old 03-20-2010, 03:36 AM   #4
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I suppose from my cap and ball pistol, I would entertain dimples that are engineered over natural. As for conicals, I want them to spin with the rifling, not like a golf ball. Plus, I have a nasty slice or hook. That depends on if I am golfing right or left handed. That's right...

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Old 03-20-2010, 09:54 AM   #5
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Interesting concept, but there is a world of difference between the rotating speeds and forward velocities of a golf ball and a high speed bullet. Maybe the laminar/turbulent flow boundary effects and the pressure profile that make a golf ball lift and carry would work, but I have my doubts.

But what do I know? I am just an old fart who hates change!

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Old 03-20-2010, 01:49 PM   #6
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LOL...I see Master Cane has started "April Fools" day early!

Besides, this was supposed to be classified intel.

Dimpled Bullet Spoof Continues to Fool Web Readers AccurateShooter.com Bulletin

U.S. Army Team Tests Radical New Dimpled Bullet AccurateShooter.com Bulletin

Jack

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Old 03-20-2010, 02:48 PM   #7
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Thanks for the report 'Cane. However, my favorite dimples are on a pretty gal's face.

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Old 03-23-2010, 02:45 PM   #8
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Some patch round ball shooters have been doing this for a while. You know the rough glass of refigerator shelves they roll the round ball between two pieces of the glass and presto dimpled round ball. Don't ask me how they shoot I haven't tryed it yet.
F.K.

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Old 03-31-2010, 04:46 AM   #9
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This seemed to be on a lot of people's minds around the time Myth Busters did they're special about the dimpled car getting better gas mileage.
I admit, I was one of the people thinking of this when I watched the episode and figured it might work. With new metalurgy techniques and computer tech assisstance I figured someone else would have the same general idea with the actual resources to try it.
I'd actually like to see this idea be implemented one day if it works, it means I actually had a good idea at about the same idea as someone else did

Imagine using the sort of crio treatment like Benelli uses on their barrels to make the surface area more smooth and uniform molecularly, this dempling affect and a slippery surface area lubricant that doesnt burn up from the temperature of firing of the bullet all in a (possibly boat tailed) 338 Lapua Magnum caliber.
It'd be one of the most expensive bullets ever made but it'd be a sniper's wet-dream.

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Old 03-31-2010, 12:35 PM   #10
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