Guns & Outdoors Forum

Watched a video of gel penetration.
I know, gel isn't definitive when compared to bone and tissue, but the test revealed an interesting finding.

FMJ round nose did not penetrate as deeply as FMJ flat nose.
The flat nose penetrated significantly deeper that the round nose, in both the 9mm and .380. So much so, that it completely passed through the second block of gel whereas the round nose only penetrated a few inches into the second block.

Theories?

Round nose only displaces gel enough to slip through and has more surface area producing friction. The flat nose causes a small temporary cavity in front of it and makes it easier for the bullet to travel farther into the gel with less friction. Just a theory…

Jeff Cooper observed the same thing with .45 ACP, that's why he espoused jacketed truncated cone for a while.

It is related to the shape. The velocity is very close between round and flat and the weight is the same. Example Winchester white box 115gr fmj is about 1150. Winchester 115 flat nose velocity is almost identical.

Would be interesting to look at higher velocity ammo like 44 mag or 357 to see if flat nose penetration exceeds fmj loads

Just a note we have the hd 9mm loaded with 147gr flat nose +p. Hope that’s a reasonable choice.

They all fall to hard ball.

Japhy wrote: ↑Sun Nov 19, 2023 2:37 am It is related to the shape.
...
Would be interesting to look at higher velocity ammo like 44 mag or 357 to see if flat nose penetration exceeds fmj loads
...

Yup, it's related to the shape.

As to the second, I'm guessing it'll depend on the size of the meplat. If it's a full wadcutter size or close to it, I would expect it to penetrate slightly less than ball (all other parameters being equal, including SD).

Once we get into the higher velocities, we start dealing with the inefficiencies resulting from those higher velocities.

My THEORY is, that the flat nose is causing a "cavity" to form where the is less of the sides of the bullet being affected by drag from the gel, while the RN does not cause that same cavity and the entire area of the sides of the bullet are suffering from the drag of the gel on it.

Apparently it's a thing.
This guy proves it with gelatin:

https://m.youtube.com/watch?v=7a6uCLdUOQI

Maybe it cuts a better hole similar to the way a wad cutter cuts paper.

And how much wad would a wad cutter cut if a wad cutter could cut wad?

When I was competing, loaded .45acp with lead truncated cone ammo. I can see where it would have an application. Too bad reloads aren't considered proper for defensive ammo.

The test shows the penetration in gel. Gel is liquefied at the impact point. Wonder if there is a difference when the target is more rigid? Like wood, layers of paper, layers of cloth or leather, or metal?

Wambli Ska wrote: ↑Sun Nov 19, 2023 1:19 am Round nose only displaces gel enough to slip through and has more surface area producing friction. The flat nose causes a small temporary cavity in front of it and makes it easier for the bullet to travel farther into the gel with less friction. Just a theory…

I think that's about all it can be.

There's been statements for years to the effect that the full diameter shoulder on a Keith-style SWC never actually gets wet on a game shot - at least not until it's slowed to the point where there's no longer a bow wave.

What I find fascinating is that they do such a good job staying point-forward without that drag along the sides preventing them from swapping ends and tumbling to heavy-end forward. I wonder how much of that is rotational inertia from the rifling.

Bigslug wrote: ↑Sun Nov 19, 2023 7:05 pm

Wambli Ska wrote: ↑Sun Nov 19, 2023 1:19 am Round nose only displaces gel enough to slip through and has more surface area producing friction. The flat nose causes a small temporary cavity in front of it and makes it easier for the bullet to travel farther into the gel with less friction. Just a theory…

I think that's about all it can be.

There's been statements for years to the effect that the full diameter shoulder on a Keith-style SWC never actually gets wet on a game shot - at least not until it's slowed to the point where there's no longer a bow wave.

What I find fascinating is that they do such a good job staying point-forward without that drag along the sides preventing them from swapping ends and tumbling to heavy-end forward. I wonder how much of that is rotational inertia from the rifling.

THAT might be worth some science!

Back in the 1980s when I carried a 1911 (on the secret as the issue was a model 63) it was difficult to find a 1911-friendly ammo. Choices were limited, either hardball or silver round bullets, can't remember the name of the silver hollow points. The 1911 ammo was also not like it is today, and I think the 1911s are made differently to take advantage of the current ammo.

Gene L wrote: ↑Sun Nov 19, 2023 11:22 pm Back in the 1980s when I carried a 1911 (on the secret as the issue was a model 63) it was difficult to find a 1911-friendly ammo. Choices were limited, either hardball or silver round bullets, can't remember the name of the silver hollow points. The 1911 ammo was also not like it is today, and I think the 1911s are made differently to take advantage of the current ammo.

We kinda got the best of both worlds for the .45. The feed ramps got wider to deal with non-hardball noses, and the ammo has trended away from truncated cones and more toward hollow points that tend to make the gun think it's feeding hardball.

We've got some DANDY cast bullet designs that do much the same.
That's the LBT .452 230 grain LFN, with a .31-.32 caliber meplat (nose flat). Best way I can describe it is that in feeding this bullet, it feels like the gun is closing without being loaded at all - there's that little resistance. A lot of modern HP's have similar profile. Very little of the nose is actually making contact with the barrel - it's mostly contact with the ogive.

At hardball velocity of 830 fps, it takes nine milk jugs to stop one. I've never bothered to do the same test with proper FMJ round nose, but this thread's got me intrigued. . .though I don't know that water is really going to tell us much.