FMJ Handgun Rounds In Ballistic Gelatin

[Jake'sDad]

I normally recommend FMJ when it comes to the tiny guns, for the same reason.

Added benefit is that it will feed better...... something the hollow points in .32 and .380 don't always do well....

[VelveteenMole]

I normally recommend FMJ when it comes to the tiny guns, for the same reason.

With that in mind, what's up with MacPherson's shape factor being .69 for round nose FMJ but only .66 for truncated cone FMJ? We've all heard folks say they carry flat point FMJ in their BUGs since it presents a sharper edge and flat face to hopefully crush a larger amount of tissue ahead of it than a more piercing/stretching effect of a round nose. The logic seems reasonable. Does anyone know how he determined round nose actually crushes a small bit more than a flat point?

[TiroFijo]

One thing is a sharp and hard bullet with a large metplat in proportion to its diameter (a full wadcutter, or a LWN design in a large caliber), and another a normal TC design (specially for autos) where the metplat is not very large and has rounded edges. Perhaps McPherson was talking about this last case.

0.69 to 0.66 is only a 4.5% increase... I would not loose any sleep over it.

[BuckskinJoe]

0.69 to 0.66 is only a 4.5% increase... I would not loose any sleep over it.

Perhaps, I am picking nits, but, when comparing bullet sizes, one must compare cross-section area, not diameter.

Divide 0.66 by 2, square the result and multiply by pi to get 0.342
Divide 0.69 by 2, square the result and multiply by pi to get 0.374

Therefore, going from 0.66 diameter to 0.69 is a 9.4% increase, which is still small but non-trivial.

Yeah, I know--picky, picky, picky!

[Jake'sDad]

One thing is a sharp and hard bullet with a large metplat in proportion to its diameter (a full wadcutter, or a LWN design in a large caliber), and another a normal TC design (specially for autos) where the metplat is not very large and has rounded edges. Perhaps McPherson was talking about this last case.

0.69 to 0.66 is only a 4.5% increase... I would not loose any sleep over it.

Velveteenmole has a good question though. Why would even a TC, have a lower number than a RN?

[bernieb90]

Velveteenmole has a good question though. Why would even a TC, have a lower number than a RN?

When Macpherson refers to truncated cone he is talking about bullets that look like this.



The actual meplat of the bullet is very small, and the sloping shoulders lack any sharp edges. The result is reduced wound trauma compared to a round nosed projectile which is blunt, and provides more resistance.

True WFN, large meplat bullets tend to behave like cylinders that are the diameter of the meplat. Keith style bullets behave similarly.

I recall an experiment done where a Keith bullet was marked with a sharpie, and fired into a test media. The marker on the shoulder of the bullet was not rubbed off indicating that during penetration the shoulder did not make contact with the media.

[TiroFijo]

BuckskinJoe, you are right about the area being 9.3% larger... still a very small difference to me. And of course, since we are happily including decimals in our calculations we must remember those are only estimates, the actual number varies with the specific design of the bullet point/ogive.

For example, one thing is a fairly blunt "round nose" like the 45 and 380, and another the typical 9 mm ogive, commonly named round nose too.

[Jake'sDad]

I remember when the Air Force was doing their ammunition testing back in the 80's and had given the TC 9mm bullets such high scores compared to RN FMJ's. I don't know the efficacy of their testing protocols, but it always seemed to make sense to me. iirc, the Hornady TC .45's and 9's were developed in conjunction with that testing.

[Shawn Dodson]

Velveteenmole has a good question though. Why would even a TC, have a lower number than a RN?

The flat meplat pushes tissue radially away from the ogive and shank, creating a small temporary cavity.

According to MacPherson an unexpanded JHP bullet has the same shape factor (.66) as a TC bullet.

I suspect the blunter meplat of a RN bullet contacts and crushes tissues before the tissues have the chance to stretch and "flow" around the elliptical ogive, which might explain why the RN has a greater shape factor than a bullet with a simple conical nose.

In addition to the pointy meplat, a conical bullet probably propels tissues radially outward more efficiently than the round nose's elliptical ogive contours. Finally surface area of a conical ogive is less than the surface area of a elliptical round nose.

More and more modern missile designs use a nose fairing with a conical nose cap, which appears to reduce aerodynamic resistance and increase velocity and range (e.g., the Peacekeeper missile, Space Shuttle solid rocket boosters, and I've seen experimental conic-elliptical nose fairings on MRLS rockets). I've wondered if a bi-conic or a conic-elliptical ogive on a long rifle bullet might allow it to penetrate the atmosphere more efficiently than a a common elliptical ogive.

[200RNL]

This data was published in the December 1974 and June 1975 FBI Law Enforcement Bulletin. It does provide a comparision on the behavior of non expanding handgun bullets while penetrating the test media.

Comparison of the Wounding Effects of Commercially Available Handgun Ammunition Suitable for Police Use

Southwestern Institute of Forensic Sciences
Dallas Texas

Energy lost when fired through 20% gelatin blocks 10 degrees C
Blocks 16cm Height 16cm width 15cm depth

Service Automatics: muzzle velocity fps......energy lost ft lbs

9mm winchester 115fmj-rn......1132......107
9mm remington 124fmj-rn......1108......110
9mm s&w 115fmj-swc......1160......176
9mm remington 115jhp......1196......330

45acp remington 230fmj-rn......812......117


Service Revolver: muzzle velocity fps......energy lost ft lbs

38spec remingtom 158rnl......789......72
38spec winchester 158swc......930......136
38spec western 150mt*......972......136


Small Automatics: muzzle velocity fps......energy lost ft lbs

380acp winchester 95fmj......866......74
32 acp remington 71fmj......912......66

25 acp remington 50fmj......774......47
22 lr winchester 40rnl......955......67

*conical metal tip/metal piercing