Huh? Slower FN penetrates more than Faster RN?

[Dannix]

The RNs compared to each other make sense with regard to respective penetration given their respective velocity. But the slightly slower FN penetrates slight more.

http://img26.imageshack.us/img26/4232/goldenloki380jacketed.png
Source: GoldenLoki .380ACP Gel Tests (http://www.goldenloki.com/ammo/gel/380acp/gel380acp.htm)


Any thoughts on what's going on here? I understand FNs just poke holes in game beyond ~1400fps. Perhaps there's a lower fps range as well where the FN does not transfer energy to the target as well either? Certainly "dwell time" is not an issue at 837fps though.


(As a side note, it looks like Speer nailed it when they designed their .380 GoldDot, edging out the Critical Defence.)

[nicholst55]

I don't think I'd worry about one inch of penetration, one way or the other. Once you get beyond 12" of penetration, you're pretty much good to go, IMHO. IIRC, that's what the FBI determined when they did all their testing after the Miami Shootout.

[Smoke-um if you got-um]

I looked at the web site and I could not find how many rounds they used for each test. Could be they just used one round of each. If they used an arbitrary number, say 10 each, the average may have been statistically closer. Just a guess........ Some of the hollow points didn't fare to well. The ones that did looked pretty good though. 10 years ago almost none of them would have expanded, if any. The technology has improved at an almost unbelievable rate. Back in the 70's or early 80's (?) the Dallas Police Department did some tests using paraffin wax in the nose cavities of hollow point bullets and achieved some decent success with getting the older tech bullets to expand. Wonder what the bullets that failed the expansion test on this web site would have done with a little paraffin in the nose ?

Mike

[44man]

Several reasons! The round nose bullets tend to want to tumble when they hit. The FN will go straight.
The pressure wave formed from the flat nose also moves material away from the side of the bullet, reducing friction.

[MtGun44]

There is considerable field experience that shows that RN at high velocity penetrate less, in
some examples, much less than the FN at moderate velocities.

One good report is Brian Pierce's experience with the FN Corbon .45-70 ammo which is a 405
gr FN with a very thick copper jacket that does not deform, at about 1600-1700 fps. He
shot a big male Cape Buffalo broadside on the shoulder, full penetration of it and the cow
buff behind it! The final shot entered the rear end and stopped against the gristle shield on
the chest after passing thru the heart - end to end!

The PH's could not understand it at all. They said that they had see a great many buffs shot with
all of the very powerful "elephant rifles" with lots of standard non-expanding bullets and none
of them would do this. Much higher velocities (2150 -2500 for the hottest) and heavier
bullets (typically 500 gr) - but the overwhelming majority are RN designs. They were very
skeptical of the .45-70 before he started shooting various game with it and showed full length
penetration of zebra, for example. They were shocked at the performance on buff.

Not scientific proof but there is more than a little bit of evidence that a flat point bullet/boolit design
penetrates better in meat than a RN. Going straighter may be the reason, seems reasonable,
but there is a steady stream of reports from the field that FNs penetrate better than RNs.

Bill

[KCSO]

I've found that above about 16-1700 fps that penetration is less too. In 1975 or so I did a lot of work with a Siamese Mauser in 45-70 and shot 500 grain hard cast against Hornady 500 grain s/p both loaded to max. The cast bullets always went deeper in all mediums than the jacketed slugs. Maybe it's like the arrow and the 30-06. All I know for sure is that every critter I ever smacked with a 45-70 wnet down, even with B/P velocities. I currently shoot a 320 HP at deer and such in deference to my shoulder and at 1600 fps they sure do the trick. I am hoping to try them on Bear this year.

[Dannix]

There is considerable field experience that shows that RN at high velocity penetrate less, in some examples, much less than the FN at moderate velocities.

Not scientific proof but there is more than a little bit of evidence that a flat point bullet/boolit design
penetrates better in meat than a RN. Going straighter may be the reason, seems reasonable,
but there is a steady stream of reports from the field that FNs penetrate better than RNs.

Bill

Well go figure. I knew >1400fps non-expanding FNs could just poke holes (http://castboolits.gunloads.com/showpost.php?p=943947&postcount=27) and some expansion for greater dwell time (http://castboolits.gunloads.com/showpost.php?p=515269&postcount=15) is desired, except that apparently poking holes isn't bad if you want massive penetration rather than a quicker energy dump e.g. seriously big game. I never really thought about nonexpanding nontumbling RNs potentially yielding better terminal damage (dumping more energy into the target) than FNs. I just figured, apparently falsely, that however much a FN penetrated, an RN would penetrate more, ceteris paribus. I guess I just didn't stop to realize that the pressure wave that was giving the FN such small hole poking deep penetration characteristcs would not be present with a RN.

I didn't catch that tidbit in the first above linked posted about needing a bit of expansion for slower stuff. I'm thankful for all the great input, but 44man and MtGun44, let me express my great appreciation for your posts in general and in terminal damage related threads particularly. They have been very insightful. :)



Several reasons! The round nose bullets tend to want to tumble when they hit. The FN will go straight.
The pressure wave formed from the flat nose also moves material away from the side of the bullet, reducing friction.
My impression is that the RNs penetrated straight in the gel test. I'll try to email the site owner there if I get a chance, to see if he can verify this. Naturally, in real world application there's bones/brush et al. In real game as Bill posts, I can understand tumbling being the reason.

I get the pressure wave idea for high fps FNs, and my impression is that the nature of the pressure wave in the 1200-1400fps range plays a part in the very effective terminal damage found for non-expanding FNs shot in that velocity envelope.


But... there doesn't seem to be a pressure wave at 800fps or so I'm guessing:


source (http://www.nennstiel-ruprecht.de/bullfly/micro.htm)
http://www.nennstiel-ruprecht.de/bullfly/fig2.gif
A .308 Winchester (7.62 x 51 Nato) FMJ bullet traveling at approximately 2800 ft/s (850 m/s). Note the change in flow type from laminar to turbulent at the bullet´s cannelure.

http://www.nennstiel-ruprecht.de/bullfly/fig3.gif
A 9 mm Luger FMJ pistol bullet, moving slightly faster than the speed of sound

http://www.nennstiel-ruprecht.de/bullfly/fig4.gif
A cal. .32 ACP (7.65 mm Browning) pistol bullet, moving at a speed considerably below the speed of sound. Only turbulences (the wake) can be observed behind the bullet´s base.

[44man]

I only hunt deer and there is not much distance for penetration. I have found 1300 to 1400 fps is good with hard boolits but when slower or faster, then some nose upset is better. My 45-70 at 1632 fps just pokes clean holes through deer, poor blood trails if any and when I finally find them, sometimes 200 yards, the lungs are mostly intact.
By just going to a softer lead without losing penetration, internal damage is great and they don't go far.
What I can't say for sure is how a fast hard boolit works on very big animals but I assume they will slow enough in passage to impart more damage.
Take my .475 with hard boolits, my 420 gr is almost a WFN at 1330 fps and it just destroys internals on deer and I would use the same boolit and load on any animal on earth.
My .44 is almost as good.
Now as distance increases and velocity starts to drop, say 100 yards, then death is slower with either caliber and they start to kill like the slower .45 Colt at close range. They still do the job but deer will go a little farther. Internal damage differences are measurable.
All of this is based on soft tissue shots, double lungs behind the shoulder. Bone hits are always deadly. I just can't hit every deer in the shoulder joint or spine off hand! :groner: That is why I demand so much accuracy from my revolvers, to cut down on my shake changes and still hit. And I shoot a LOT of deer.
Now penetration! Not much will stop my hard boolits so some upset at the nose would be fine with all guns.
I was leading a deer last season in dim light and when the .475 went off, it looked like there was brush in front of the deer. Later I found it was an osage orange tree trunk of 10" to 12" in diameter. My WFN went all the way through it. It was a double trunk so the other trunk stopped my boolit.
The deer ran back and came right around again in a clear spot so I dumped him.
We have shot through 16" trees with the .44, 45-70 and .475.
The velocity you hunt with means nothing at all. All you need to do is change the boolit so it works inside the animal before it exits.
Energy dump and muzzle energy is a myth. A boolit made proper can do as much damage at 800 fps as one at 1600 fps.
Yes a boolit needs energy but it is where it is applied and what the boolit does so if a boolit goes through an animal and still retains a lot of energy, enough to kill a second animal, you have not lost anything on the first animal because the boolit did the job.
I started hunting deer with the .44 using the 240 gr XTP. It killed fine but I recovered all three bullets with lung shots. Nice mushrooms and all energy stayed in the deer. But back tracking showed a zero blood trail. If it was thicker, I could have lost a few.
I changed to the 320 gr LBT and my own 330 gr copy and deer die faster with huge blood trails even though they still have a lot of energy after penetration.
Please do not believe in "energy dump." It will bite you! :holysheep
Here is deer damage done with a hard .475 boolit at 55 yards. The boolit had enough energy after penetration to easily kill two more deer.

[Char-Gar]

It is not the speed but the bullet shape.