Bullet lengths


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wworker
February 1, 2008, 10:34 AM
Is there any way to find out the bullet length for various bullets without resorting to opening every brand/make and measuring? The bullet manufactures websites don't have that information. My loading manuals don't have that information.

Does anybody have a link to this information?

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ranger335v
February 1, 2008, 10:50 AM
"Does anybody have a link to this information?"

I don't think so.

In some 45 years of reloading, I've never heard of anyone being concerned about the specific lengths of bullets. ????

rcmodel
February 1, 2008, 12:26 PM
I agree.
I can't think of any reason it would be important.

The important information is always provided by the bullet makers.

Diameter, Weight, Bullet Type, Ballistic Coefficient, and Sectional Density.

What else do you need to know?

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rcmodel

zxcvbob
February 1, 2008, 12:52 PM
The bullet length is very important when loading small capacity handgun cases, like 9mm. It changes the seating depth, which can make a *big* difference in pressure.

(It probably doesn't matter at all for large rifle cases)

Walkalong
February 1, 2008, 01:01 PM
I log bullet lengths when I load them. Sometimes it comes in handy because I can figure out how deep in the case it will be compared to others I have data on when trying a new bullet. Most times it is insignificant though. It's not really necessary, I just do it.

jfh
February 1, 2008, 01:05 PM
I'll agree that it can be important as outlined by zxcvbob--but only if one is out there working at the ragged edge.

Some years ago I was enamored with 9mm, and I tried all sorts of 356 / 357 bullets, from standard nine offerings on up to 158-gr. stuff. That was pretty self-limiting, however--the longer lengths precluded satisfactory seating; the case would bulge--and if it didn't, the volume was too small to put in an overpressure charge.

Cast bullet molds are now fairly stabilized in terms of design, and semi-auto bullets (typically) have no cannelure. Bullet manufacturers, of course, do provide the dimensions, including LOA (if not charted somewhere, they will if you ask).

So, gather the information for the specific bullet you want, probably by calling the manufacturer.

Jim H.

wworker
February 1, 2008, 01:12 PM
Bullet length is needed for the Greenhill calculator formula.

It has to do with finding the optimum twist rate verses bullet length.

I have a 1 in 9 twist M4 barrel and the optimum bullet length for speeds under 2800 fps is .84 inches. The only problem is I can find the bullet lengths of various FMJ (or otherwise) bullets.

I have 55 grain FMJ at home to measure, but perhaps someone can tell me what weight of bullet is closest to .84 inches in length.


WHAT IT THE GREENHILL FORMULA?

The Greenhill Formula calculates the twist rates of bullets.
The formula is as follows:

(if bullet velocity is less than 2800 ft/sec)
150 x diameter x diameter
------------------------- = required spin
length of bullet

(if bullet velocity is greater than 2800 ft/sec)
180 x diameter x diameter
------------------------- = required spin
length of bullet

rcmodel
February 1, 2008, 01:16 PM
The bullet length is very important when loading small capacity handgun casesNot if you are using the correct load data for the 9mm bullet in question.
Which you should be using.

If you are substituting one brand of bullet for another, using someone else's load data, I can see bullet length being something that would be nice to know.

But other factors such as jacket hardness, and bullet construction, are just as important, if not more so, in raising pressures as the length of the bullet.

If you are using generic data, with an different bullet, you are in unknown territory already, regardless of the bullet length.

http://i81.photobucket.com/albums/j219/rcmodel/KTOG/1224.gif
rcmodel

rcmodel
February 1, 2008, 01:21 PM
Don't get to wrapped up in the Greenhill Formula.

It was devised over 100 years ago, when long, streamlined, plastic-tipped or HP, boat-tail bullets were not the norm.

At best, it will give you a ball-park number.
At worst, it will be wrong.

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rcmodel

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