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Old March 12, 2012, 10:32 PM   #1
RH
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Caliber dictates bullet shape?

This may be the best place to ask this question. Why is it that certain calibers have very distinct bullet shapes, and no matter the loading or the manufacturer, the bullet shapes do not vary that much? For example, .223 is always pointy, .17 HMR even pointy-er. 30-30 is always rounded or blunt tipped. .308 are pointy. Most .22 LR has some flavor of "sealing rings" around the base of the bullet, and you never see really pointy .22's.

Is this functional, or tradition? Why don't people try different bullet types in different rounds? If .17 HMR's fly true with needle-points, why not .22's? How would a 30-30 work with a .308 boattail, or vice-versa?
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Old March 12, 2012, 10:49 PM   #2
dacaur
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Its sort of both, but more functional... Pointy bullets have less drag so fly better. .223, .308, etc, were designed with pointy bullets because it wouldnt make sense to use blunt bullets, it would decrease their performance...

The reason for blunt tips is two-fold.

#1, 30/30 and any other round that is (or was)chamberd for a levergun must have a blunt tip, or the pointed tip of one bullet could set off the primer of the bullet ahead of it in the magazine. Hornadys FTX bullets get around this problem by using super soft tips....

The other reason to use blunt bullets, is that the bullet was "invented" before pointy tips became common, they didnt know any better, And if you look at them, you will notice the bullet sticking out of the case is pretty short, so you dont have enough room to give it a long pointy tip.... .22lr and .22WMR are two classic cases of this... Hornady got around the probem by necking them down to .17 cal, giving us .17HM2 and .17HMR...
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Old March 13, 2012, 07:10 AM   #3
griz
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I'll add that 22LR has a heeled bullet. In other works, the part of the bullet that's in the case is smaller in diameter than the exposed part, so the case is the same outer diameter as the bullet. In all other currently loaded rounds, the part of the bullet inside the case is full diameter.
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Old March 13, 2012, 07:44 AM   #4
Uncle Buck
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I have 30-30 ammo with a pointy tip, it is loaded in a single shot 30-30. Put it in a tube magazine and you could possibly set off the other rounds.

I can not remember the exact term used, but it is something to do with the lowest common denominator allowing you to sell more.

In this case, .22 bullets, 30-30 bullets, etc. There are specialty rounds out there and available, but you will not very likely find them on the shelves of your local sporting goods store. Why should they stock something that one in a million customers might purchase?

The 30-30 and .308 and most cartridges in between take the same size bullet. If you reload, you can change bullets to the shape you desire for the performance you desire.
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Old March 13, 2012, 07:55 AM   #5
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In some cases, the shape of the bullet is due to the design of the firearm. Tube magazine,centerfire rifles must use blunt bullets to prevent chain fire in the magazine.
Other cases involve the traditional type and twist of the rifling. A round nose bullet is shorter than a "pointy" bullet and will be accurate in a slower twist rate such as is standard in the 22lr for it's entire life.
Many more modern cartridges have gone through a transition from round nose to spitzer(pointy) during their life. Early military designs used round nose bullets. The 6.5x55,7x57,and 30/03(30/06) are examples of this among others. Their original designs used a heavy,long, round nose bullet but the design was capable of supporting the change to a lighter, shorter, pointed bullet.
This info is fairly general and jumps over much more specific points of this topic.
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Old March 13, 2012, 08:03 AM   #6
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More precisely, application (intended use) dictates bullet shape- "Form Follows Function", "Right Tool For the Right Job", etc.....

-Pistol ammunition for short range target games with paper targets are shaped with sharp edges (wad-cutters, semi-wad cutters) to cut clean holes in the paper targets to make keeping score easier..... high velocities are not necessary, so un-jacketed lead can be used.

-longer ranged games games like silhouette shooting need high velocity, heavy bullets to knock over distant heavy steel targets..... bullets are long, pointed, often boat tailed, and usually jacketed/gas checked (if rules allow) ....

-personal defense is a short ranged proposition, usually, where the user needs the bullet to create as large a wound as possible, to stop the assailant as fast as possible, without the bullet passing completely through and possibly stiking somone else ..... thus the hollow point, or a hollow point filled with polymer ......
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Old March 14, 2012, 09:13 PM   #7
thedaddycat
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As stated above, most .30-30 bullets are either round nose or flat point due to the risk of chain fire in the tube magazine. Bullets at places like Cabela's and other suppliers will have these bullets marked as being for the .30-30. Most factory ammo is also usually either 150 grain or 170 grain.

The fact is that vurtually all .30 cal chamberings use .308 diameter bullets. An exception would be the .303 British which uses a .312 diameter bullet. Some will say that it is not a true .30 cal while others classify it that way. Now it is possible to use other bullets of different shapes in the .30-30. A couple of solutions are to use a single shot action or only load a single round in the magazine, effectively making the typical lever action into a two shot rifle(load one in the chamber and then one in the mag). Another solution from long ago was to use a spiral shaped tube magazine which allowed the tips to be offset from the primers.

In theory you could load any .308 bullet into a .30-30 case and it should chamber and fire. The risk is that someone who is not aware of the dangers of chain fire could use them in a tube magazine...
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Old March 14, 2012, 11:09 PM   #8
dacaur
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Other than hornady FTX, I have never seen 30-30 rounds loaded with pointed bullets, most pointed bullets simply wouldn't work in a 30-30....
The ogive on most .30 cal spire point bullets to too shallow for 30-30. In order to load to the correct COAL, the bullet would be so deep in the case that there would be space between the case mouth and the bullet.
The hornady FTX bullet has a very steep ogive to keep the COAL correct, its not an "ideal" shape, but its better than round, so there is a performance increase.

Such is the case with most bullets with round profiles still in use out there today. In order to have a properly pointed bullet, would require the COAL to be too long, so they stick with round nose, because significantly changing the COAL would mean the bullet wont work in many guns chambered for it, so the ammo makers out there wont do it. You could do it yourself in a one-off project, but there's not much point to it, unless its something that you just want to do for whatever reason....
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