Why do some bullets have belted indentations like in this picture?

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this, fucking lowIQs this summer

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It's so when you shoot an intruder and they run away you can collect the bullet and the perps blood will be stored in the ridges for DNA testing.

Generally a crimp groove on jacketed rounds, and lube groove for cast lead.

Cool. Could you exain this further im a noobasauras

Im just guessing but its probably for the same reason large caliber pellets and musket bullets are too. For reduced surf contact with the barrel causing less friction and higher velocity.

Interesting. Do the spaces maybe allow room for the bullet to deform into as the rifling lands squeeze it into shape on its way through the barrel?

A lot of brass cases get crimped around the projectile to prevent them from slipping out/in. The crimp lines give you a location to crimp into without marring up the side of the projectile. If you're using cast lead, the lube cuts back on lead fowling I think.
Pic related is a cast lead bullet with lube--a dry waxy substance.

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Im not sure for centerfire projectiles but for the other projectiles, no. It simply keep more material from touching the rifling which reduces friction. If you have a few ribs touching the rifling its easier to push through than if you had the whole length of the bullet making contact.

>flat surfaces have more friction than bumpy ones
Explain sandpaper you retard

ribbed for pleasure

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Wrong

Really, sand paper.
OK, try to use a softer sand then the substance you are trying to sand.
Such as trying a bread crumbs on a steel, you will discover that friction is not the same as stonesand on wood.

>bumpy surfaces have less surface area
>flat surfaces have more surface area contacting

Holy shit you are a fucking brainlet.

>replying to bait
The real brainlets are always in the comments

Crimping the jacket over the core helps to prevent jacket separation once it hits the target, ensuring more consistent wound patterns and increasing penetration.

Jesus christ you obviously failed high school physics.

OP the groves make it more lethal and are used by police SWAT and military. They are called blood groves and they make the wound more likely to stay open and bleed

Why/how would grooves prevent jacket separation?

Tbh it's probably not bait, he's probably just a kid. Virtually every kid I knew back in the day thought ridgier tired meant better grip.

Its for your pleasure

In the case that user is describing, the bullet jacket is crimped onto the core. The groove you can see doesn't do shit, but if you were to cut through the bullet so you could see the interior you would see that the jacket is compressed into the core at the location of the groove, mechanically locking the two together.

You are talking about the bore-rider bullet design.
The point is not friction, rather it's having less metal to engrave rifling onto. Adding those grooves to the bullet resembles the idea of a narrow driving band on an artillery shell.

>lead fowling
I've heard about the "spruce goose" but this is ridiculous!

nobody fucking knows, man

This happens with bonded jackets.

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jacket bonding is a chemical process and has nothing whatsoever to do with a cannelure.

Only correct answer.

The grooves give the jacket material displaced by the rifling somewhere to go. Reducing friction is secondary.

TSX bullets have no jacket.
They are a bore riding bullet with driving bands. They are too hard to engrave the rifling like a normal bullet.

You have no idea what you're talking about. Just think about it for two seconds. A bore riding bullet wouldn't fit securely in a normally sized case for its caliber, but TSX bullets do.

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