Question: .40 S&W FMJ and penetration/damage capability


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Weedy
January 14, 2010, 05:29 PM
I had another middle of the night thought...

Ok, most hard-cast lead bullets designed for hunting/defense have flat noses and wide meplats. Based on the various things I've read on the internet, the wide meplat itself can cause almost as much destruction of tissue as an expanding bullet (I haven't seen this firsthand, just things I've read.) .40 S&W FMJ bullets have pretty wide, flat noses. Most 9mm (except some 147gr I've seen) and .45ACP I've seen have had round noses, and therefore seem to "zip" right through things, causing little damage. So I'm wondering, will a flat-nose .40 FMJ bullet perform similarly to a flat nose hard cast lead bullet? Will the meplat of a FMJ bullet cause as much damage as the meplat of a hard cast one? I can't find any gelatin tests of .40 FMJ bullets. It seems possible to me that a flat nose .40 S&W FMJ could do quite a bit more damage than the regular round nosed FMJ rounds of other calibers.

Help, I lost like 2 hours of sleep last night because of this! :uhoh:

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Paints
January 14, 2010, 06:43 PM
FWIW, I've have wondered if SWC bullets would not be highly effective.

I agree that the flat nose is better than round nose. That's what I have in my Keltec P32, but I only carry that a couple of times a year.

Ken

Manco
January 14, 2010, 09:12 PM
Ok, most hard-cast lead bullets designed for hunting/defense have flat noses and wide meplats. Based on the various things I've read on the internet, the wide meplat itself can cause almost as much destruction of tissue as an expanding bullet (I haven't seen this firsthand, just things I've read.)

The concept is that like expanded hollow-points, they're shaped to devote more of the bullet's energy to crushing the tissue directly in the bullet's path rather than making a minimal tear and stretching the tissue apart temporarily in order to penetrate like round-nose bullets do. Being narrower than expanded bullets, they won't damage as much tissue per depth of penetration, but they will penetrate more deeply, which is the trade-off.

.40 S&W FMJ bullets have pretty wide, flat noses.

I just measured some Winchester USA (AKA white box), Federal American Eagle, and Speer Lawman FMJ rounds that I have on hand (I buy whatever is available or on sale :)), and they all have meplats that measure somewhere between 5 and 6 mm.

Most 9mm (except some 147gr I've seen) and .45ACP I've seen have had round noses, and therefore seem to "zip" right through things, causing little damage.

That's why I keep telling people that the difference between these two calibers is minimal with FMJ rounds (at least typical ones). Not that the difference is tremendous with JHPs, either, but it's far more pronounced.

So I'm wondering, will a flat-nose .40 FMJ bullet perform similarly to a flat nose hard cast lead bullet? Will the meplat of a FMJ bullet cause as much damage as the meplat of a hard cast one?

Presumably the same principles apply, although hard-cast bullets usually have wider meplats (about 8 mm for .40 S&W and 10mm Auto) and minimal beveling at the edge, making them more effective than typical FMJ-FN or FMJ-TC bullets at what they do. There is also the issue of deformation and fragmentation after hitting something hard such as bone, which may hamper the FMJ bullets' ability to penetrate (at least for the purpose of hunting or defending against larger animals than humans).

I can't find any gelatin tests of .40 FMJ bullets. It seems possible to me that a flat nose .40 S&W FMJ could do quite a bit more damage than the regular round nosed FMJ rounds of other calibers.

That would be interesting to see. Generally flat-nosed bullets penetrate just as well as round-nosed bullets from what I've seen of other calibers, at least in gelatin.

FWIW, I've have wondered if SWC bullets would not be highly effective.

Sure, people have long used them as defensive rounds in order to ensure adequate penetration against human targets with more marginal calibers. This hard-cast, gas-checked (you wouldn't want to swage this bullet through the barrel ;)) round kind of resembles a SWC:

http://www.doubletapammo.com/php/catalog/product_info.php?cPath=21_26&products_id=210

With .40 S&W, however, the best type of bullet to use against humans would be JHPs.

Majik
January 14, 2010, 09:31 PM
40 rounds come in pretty heavy but still travel pretty fast. They'll penetrate deep, are heavy enough to smash through solid bones without deflection, and they start with a .4 with 15 rounds in the magazine of a standard 40 s/w pistol that is smaller framed than a 45 acp.

The JHP's are good for penetration of barriers and bones, with the 40.

Manco
January 14, 2010, 11:38 PM
FWIW, I've have wondered if SWC bullets would not be highly effective.

Look at the damage caused by the .38 Special SWC bullet in the video referenced by Majik in another thread (you might want to read that whole thread, too):

http://www.thehighroad.org/showpost.php?p=6191024&postcount=29

It apparently cuts a ragged .357" diameter hole through the gelatin, in contrast to FMJ rounds that punch through like an icepick (with a barely visible track) and the hollow-point bullets that do the same until they expand. Indeed, it seems that nearly all of the SWC bullet's energy goes into crushing the gelatin it touches directly instead of generating a sizable temporary cavity. The question is whether it does the same in flesh, which many seem to believe (hence the shape of hard-cast bullets designed for hunting and woods carry).

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