Would adding cannelure to bullet do more than just lower BC?

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Would adding cannelure to bullet do more than just lower BC?

Post by fordj » 29 Sep 2014, 11:39 am

Half baked idea in progress here... Indulge me for arguments sake...

It would make sense if you added a cannelure to the body of a bullet without one you'd lower it's BC.

Would that be it though? If you had an accurate bullet your wanted to add cannelures to for crimp loads would that be the only impact or could/would it potentially change the whole thing and how it shoots?
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Re: Would adding cannelure to bullet do more than just lower

Post by Chronos » 29 Sep 2014, 12:05 pm

Where do you get the idea adding a cannelure to a bullet will lower its BC?

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Re: Would adding cannelure to bullet do more than just lower

Post by Timb0 » 29 Sep 2014, 12:47 pm

I completely misread that post. I guess I shouldn't be on my phone while walking around the shops!

Hornady's .270 130gr interbond and their 270 130gr SST have the same BC the only standout difference is the cannelure on the SST.

I haven't seen any interbonds for a long time though....
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Re: Would adding cannelure to bullet do more than just lower

Post by fordj » 29 Sep 2014, 4:04 pm

Chronos wrote:Where do you get the idea adding a cannelure to a bullet will lower its BC?


Just seems like adding a ridge and edge to the body would do it? Make it not quite as streamline any more?

Open the possibility of being wrong here, it has happened before :lol:
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Re: Would adding cannelure to bullet do more than just lower

Post by Chronos » 29 Sep 2014, 4:33 pm

I think you may have BC balistic coefficient and CD coefficient of drag mixed up.

From what I remember CD gives a value if 1 to a flat board traveling through the air. In that example the lowest number is desirable, a car with a CD of .5 is more aerodynamic or creates less drag than a car with a CD of .6

In ballistics I believe a value of 1 is given to a projectile that is so efficient it encounters zero resistance through the air ( probably impossible except for in a vacuum)

In the case of a bullet one with a BC of .4 will encounter more air resistance than a bullet with a. BC if .6 therefor it will maintain its velocity longer, arriving earlier and drop less. Remember gravity is constant so it's flight time that affects drop, not weight.

A cannelure would reduce the bullets aero efficiency making it slow down faster therefor making the time to target longer and the drop more

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Re: Would adding cannelure to bullet do more than just lower

Post by 1290 » 30 Sep 2014, 11:14 am

CD is the drag coefficient, measure of the 'drag' of the object while the BC is a measure of the efficiency of the projectile in comparison to a standard projectile with a particular shape. you can have a (G1) BC greater than 1... such as many 0.5 cal bullets...

CD / BC are inverse (not directly) just like the thermal 'R' and 'U' values, one being related to the thermal resistance and the other thermal transfer...

Yes, the cannelure will increase the drag, there is little doubt. given that it will disrupt the streamline..... Chronos, imagine a world where everyone agreed all the time!!.

What is the magnitude of the decrease in the BC? probably below measurable quantities given that manufacturers (as far as I recall) list same BCs for cannelured/non-cannelured projjies of the same type/shape/mass....
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Re: Would adding cannelure to bullet do more than just lower

Post by fordj » 30 Sep 2014, 12:10 pm

Timb0 wrote:Hornady's .270 130gr interbond and their 270 130gr SST have the same BC the only standout difference is the cannelure on the SST.


Cool, thanks Timbo.
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Re: Would adding cannelure to bullet do more than just lower

Post by fordj » 30 Sep 2014, 12:12 pm

Chronos and 1290,

Thanks for the replies and info. I'm out of my depth now adding drag coefficient to the mix TBH, I like to understand though so will do some research on this too to get my head around the whole package.
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Re: Would adding cannelure to bullet do more than just lower

Post by bunnybuster » 03 Oct 2014, 1:30 pm

How much of a rolled cannelure survives after the proj is forced [swaged] into the rifling is debatable and I'm not volunteering to hold the catchers mitt to look at it before it impacts the game, but IMHO it's not even worth considering,

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Re: Would adding cannelure to bullet do more than just lower

Post by 1290 » 03 Oct 2014, 2:03 pm

depends on the chambering, the 223 Rem swages down 0.01mm, the the rifling engraves a further 0.13mm. Comparing the 308win swaging down 0.03mm then the rifling a further 0.2mm.

So the 223 will have more of the cannelure left.... the rifling will then only engrave a small part around the circumference...

Some chambering do not swage down, only partly engrave he rifling....(303Brit, 6.5x55SE, etc)
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Re: Would adding cannelure to bullet do more than just lower

Post by meateater » 06 Oct 2014, 10:08 am

bunnybuster wrote:I'm not volunteering to hold the catchers mitt to look at it before it impacts the game


Is there a way to catch a bullet without any expansion? Some special chamber they shoot into or something?
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Re: Would adding cannelure to bullet do more than just lower

Post by Hinky » 06 Oct 2014, 1:54 pm

If I'm thinking of what you're thinking off... They do have ballistic traps or something I think they're called that the cops fire guns into for bullet comparisons.

AFAIK though they're just filled with water and the bullet still deforms, they just use the back half of it to match the rifling.

That's one kind anyway.
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Re: Would adding cannelure to bullet do more than just lower

Post by Apollo » 06 Oct 2014, 2:10 pm

How can a Cannelure affect the ballistics of a bullet to any extent as it's along it's bearing surface. Not the nose or the tail which both have a major affect on a bullets flight/ballistics.
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Re: Would adding cannelure to bullet do more than just lower

Post by 1290 » 06 Oct 2014, 5:00 pm

Hinky wrote:If I'm thinking of what you're thinking off... They do have ballistic traps or something I think they're called that the cops fire guns into for bullet comparisons.

AFAIK though they're just filled with water and the bullet still deforms, they just use the back half of it to match the rifling.

That's one kind anyway.


Those science tools on Mythbusters did the shooting into the water test; the sonic/subsonic rounds hold their form and penetrate while the supersonic rounds, normal rifle rounds disintegrate practically on impact with water....9x19 goes 9+ feet and still through the gel, 50BMG disintegrates in 2 or 3 feet, surprisingly.

So water should stop pistol rounds without deforming them...
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Re: Would adding cannelure to bullet do more than just lower

Post by meateater » 08 Oct 2014, 9:19 am

Yeah I saw the Mythbusters episode.

They were shooting into the pool from a few metres away though where the bullet would still be hitting with max energy and disintegrating like you said.

I was thinking of doing it at distance to wash off the energy or using something to slow it over a longer distance instead of catching it within a few feet.
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Re: Would adding cannelure to bullet do more than just lower

Post by MrClark » 14 Oct 2014, 10:07 pm

Correct me if I'm wrong and I probably am :lol:

But for the same weight and shape projectile one without a cannelure would have a higher (although only just) BC but the projectile with the cannelure would have less bearing surface on the rifling reducing friction and may have a slightly higher muzzle velocity?
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Re: Would adding cannelure to bullet do more than just lower

Post by Tiiger » 15 Oct 2014, 2:23 pm

All sounds good in theory Clarky.

Shoot them though you'll probably find it means bugger all :lol:
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Re: Would adding cannelure to bullet do more than just lower

Post by Jack V » 15 Oct 2014, 4:14 pm

Aside from any slight change in aerodynamic air flow , adding a poorly applied cannelure could also potentially upset rotational balance ( gyroscopic stability ) affecting group accuracy.

Any additional thing that you do to a projectile has the potential to upset it's performance. Most factory crimp dies don't need a cannelure as the collet is so powerful it kind of makes it's own groove.
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Re: Would adding cannelure to bullet do more than just lower

Post by AusC » 19 Oct 2014, 11:08 am

Too much focus on BC... Shoot 'em and keep the most accurate one.
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