FMJ Separation

[wingspar]

Is this normal? I picked this up yesterday after running an entire box of 9mm thru my Glock. The bullet passed thru a ½ - inch piece of plywood before impacting dirt about 3 feet behind the plywood. This is the only bullet I found, and was surprised to find this one. Whether it’s common or not, I don’t remember picking up a bullet that had separated from the jacket.

WWB 115 grain FMJ.

[Maximilian II]

I find it pretty often with flat-nosed soft points from my .44mag, but not with FMJ's.

What did it hit? If the copper "tore" upon hitting harder surfaces like metal, this could easily happen.

[wingspar]

Actually, I wrote what it hit in my first post.

And, I didn’t put it here, even tho it is ammo related, I put it in General Discussion so it would get more views and more comments.

[cakes]

Every once in a while I will scoop up a couple gallons of bullets from the berm at the local range. The first time I did I was surprised at the number of empty jackets I found in the berm. The target stands are plywood.

[Bindernut]

Yup, I've had a lot of jacket separations on FMJs if they hit something fairly solid (like a wood backstop plate.

You have to think of an FMJ bullet as a soft-point that's loaded upside down. It's still a lead slug in a copper jacket and swaged together...the opening in the jacket is just on the rear instead of the front.
Some companies actually have the lead and copper bonded together (like Speer's uni-core process) but most of them are made with two loose parts swaged together when they're formed/sized. If the jacket gets tore up enough from hitting something solid, it can peel open and let the core escape (like the bullet that you've got pictured).

[wingspar]

Well, I was surprised because it was just plain dirt, with maybe a piece of rock up to two inches in size. I’ve shot harder targets without seeing this. If I was shooting a hard rock or steel targets, then I wouldn’t have thought much of it. I’m surprised I don’t see it more often. The dirt was soft enough, that this is the only bullet I found out of 50. I’d have needed a shovel and a screen to find more.

Here are some I did a month ago. These were also shot thru ½ inch plywood, but in back of the plywood this time was a steep sandstone face. The sandstone is in a road cut, and stands fairly steep, but is not solid rock, as it turned to sand where the bullets hit. What I was surprised to find were bullets all over the place. Even as much as 4 feet back towards me from the target, and plenty laying right on the surface behind the plywood.

The two bullets on the left were WWB 115 grain BEB. (Brass Enclosed Bullet) The rest are all FMJ, either 115 grain or 124 grain. No separation of the FMJ bullets, and practically no deformation of one of them at all.

[Bindernut]

If you look at some of the other bullets in that last picture you posted you can see on several of the traditional FMJ bullets the cores are starting to separate too. They just didn't peel completely apart.

That sandstone backstop is working about like a ceramic trauma plate in a bulletproof vest. It is brittle enough where it will shatter and absorb a lot of the bullet's energy, but as you noticed, it's not trapping the bullets. They just fall to the ground after all the energy is expended...or bounce back a few feet.
I hope you're shooting at an oblique angle to it so any of those rebounds are most likely to head in a safe direction.

My backstop down at the farm is a big shale/gravel bank that we have dug out for use as fill. Those small rocks, sand, and shale do a good job of boogering up but still capturing the bullets. I'll get the occasional ricochet if I do smack a small rock at the wrong angle, but most of those have been screened out from the pile that I usually set up my target butts by.

I have picked out a few bullets while loading out of my pit too...a lot of my "plinker" FMJ .380, 9mm, and .45ACP will have separated. JHPs and other soft-nose bullets usually hold together better. I wonder if it's because in a FMJ when it impacts something hard and the jacket deforms, the lead core has a tendency to get pushed out the opening in the back. While on a JHP/JSP the core is being pushed farther back inside the jacket.
Ahhh...theories!

[wingspar]

Can’t say that I was shooting at an oblique angle, cause I just didn’t expect this. I expected some penetration into the sandstone. It was getting dark, but I bet if I go back up there, I’ll find a lot more bullets just laying around, and maybe one where there is jacket separation from the bullet.