Six Inches of Sand to Stop a Bullet

[Ben]

This was something I hadn't researched before, but I had my excavator guy out today doing some work for me, part of which was digging into my hill to make my home shooting range.

I had him dig in to the hill around 8' feet, berm up the sides, then dump a crapload of sand down the sloping wall of the backstop. I probably have close to a foot of thickness at the top and three or more feet towards the bottom (then of course the clay in the hill behind it), but was still curious about safety so did some googling.

Almost every article/test that I found had 6" of sand stopping most common pistol and rifle rounds. I honestly thought it would be a lot more than that. Anyway, learn something new every day.

https://www.theboxotruth.com/the-box-o-truth-7-the-sands-o-truth/

[RoadKingLarry]

I've dug more than 18" into hard packed shale and clay and still couldnt find full power 525 gr  BP loads from my Sharps.

[230RN]

Hatcher noted that bullets penetrate more in wet sand than dry sand.  Apparently lubricity is involved.  They (ordnance dept) did a lot of penetration tests on various calibers.  One interesting fact was that in oak, bullets from service cartridges penetrated waaay more from long range than short range.  Tentative reason? At close range, they have not completely stabilized and therefore tumble in the oak and stop quickly.

Honestly, you guys have to read Hatcher so I don't have to keep parroting answers to your questions from Hatcher.

I've said it before: despite the age of the book, it will answer maybe 80% of today's gun questions.

Nice thing about it is you can open it at random and be interested in the random information.

Terry, Hatcherophile, 230RN

[cordex]

I've dug more than 18" into hard packed shale and clay and still couldnt find full power 525 gr  BP loads from my Sharps.

You missed the whole berm.

[griz]

I thought so too.  I remember them firing straight up from a platform in the middle of a lake to measure how long a bullet took to fall back.  Lots of good info all through the book.

[MechAg94]

The problem with a berm is do you still have 6" of sand to stop the 1000th bullet, not just the first one.  I guess as long as you are checking it out occasionally you will be okay.

Seems to me at the range I belong to, there is some significant erosion of some of the berms where the bullets impact in the same area a lot.  I think they have to rebuild them occasionally. 

[Hawkmoon]

I think a reasonable ad hoc test would be to fill a 5-gallon taping compound bucket with sand to a depth of about a foot, climb up a ladder, and shoot several rounds straight down into the sand. Excavate the sand until you find where the bullets stopped.

[Northwoods]

They (ordnance dept) did a lot of penetration tests on various calibers.  One interesting fact was that in oak, bullets from service cartridges penetrated waaay more from long range than short range.  Tentative reason? At close range, they have not completely stabilized and therefore tumble in the oak and stop quickly.

Ummm.  No.  At close range the bullets impact with enough energy to deform greatly and/or fragment.  That is why they don’t penetrate oak as well as from long range, by when their velocity and hence energy have dropped below the amount needed for expansion/fragmentation. 

[230RN]

Ummm, I rely on the captions to photographs on pp 406 to 407.  These were taken for penetration at 50 feet and 200 yards with the .30-06.

I'm willing to look at later data, and the deformation theory is certainly conceivable,  but one would assume that  Hatcher would have reported any bullet deformation, as opposed to mentioning the instability of the bullet in flight at close range theory.

I looked at the "official" Errata list at:

https://yarchive.net/gun/hatchers_notebook.html

and found no mention of any corrections of those captions.

For now, pending more evidence, I'm sticking with Hatcher, as written, for the nonce.  I can certainly imagine instability as the rapidly rotating bullet leaves the barrel, but, like Ralph's Top, settling down to a stable spin after awhile.

Terry, 230RN

REF:
I believe the "Top Wars" story  appeared in the Jean Shepherd movie A Christmas Story (1983).

Correction: It runs in the family, 1994

[Ben]

The problem with a berm is do you still have 6" of sand to stop the 1000th bullet, not just the first one.  I guess as long as you are checking it out occasionally you will be okay.

Seems to me at the range I belong to, there is some significant erosion of some of the berms where the bullets impact in the same area a lot.  I think they have to rebuild them occasionally.

I left five tons of sand near the range, planning to every once in a while rebuild the backstop and berms with my little loader.

It's built well into the hill, so if sand degrades in storms or whatever, there's still the entire hill behind it. My original concern was that I thought the entire hill was pretty much pit run, which would have left to many big rocks to just dig a range into the side of the hill. Interestingly, as my guy dug into the hill, within a couple of feet it started turning into clay loam with few rocks. But I had the sand delivered before we dug, so just used it, learning of its stopping properties after the fact.

I also have a bunch of railroad ties that I found on the property, so I might figure something out stacking those as well. I found another interesting video testing how far various bullets penetrate railroad ties. It was an amateur test, just with a guy who wanted to know which of his own guns he could shoot safely on his home range, but still interesting. The first gun to penetrate was an AK. None of his pistols through .44mag did.

https://youtu.be/7ufyBfk32XY

[Ben]

Hatcher noted that bullets penetrate more in wet sand than dry sand.  Apparently lubricity is involved. 

I was surprised that the dry sand seemed to be a better bullet stopper than something like clay. The fact that dry sand doesn't really compact densely led me to think you would need a lot more than a denser, heavier per square inch, material.

[K Frame]

"Honestly, you guys have to read Hatcher so I don't have to keep parroting answers to your questions from Hatcher."

Polly want a cracker?

[K Frame]

Ummm.  No.  At close range the bullets impact with enough energy to deform greatly and/or fragment.  That is why they don’t penetrate oak as well as from long range, by when their velocity and hence energy have dropped below the amount needed for expansion/fragmentation. 

Except that the close-range impact with oak bullets that Hatcher showed exhibited very little to no deformation. They were military hardball.

Later high-speed video of bullets exiting the muzzle did show that they exhibited wobble and took time to settle down into a stable flight, not unlike how a football wobbles when it exits a player's hand, but will settle into a nice tight spiral.

[MechAg94]

I left five tons of sand near the range, planning to every once in a while rebuild the backstop and berms with my little loader.

It's built well into the hill, so if sand degrades in storms or whatever, there's still the entire hill behind it. My original concern was that I thought the entire hill was pretty much pit run, which would have left to many big rocks to just dig a range into the side of the hill. Interestingly, as my guy dug into the hill, within a couple of feet it started turning into clay loam with few rocks. But I had the sand delivered before we dug, so just used it, learning of its stopping properties after the fact.

I also have a bunch of railroad ties that I found on the property, so I might figure something out stacking those as well. I found another interesting video testing how far various bullets penetrate railroad ties. It was an amateur test, just with a guy who wanted to know which of his own guns he could shoot safely on his home range, but still interesting. The first gun to penetrate was an AK. None of his pistols through .44mag did.

https://youtu.be/7ufyBfk32XY

For just a personal range, I wouldn't expect any issues. 

[230RN]

Ben:

"I was surprised that the dry sand seemed to be a better bullet stopper than something like clay. The fact that dry sand doesn't really compact densely led me to think you would need a lot more than a denser, heavier per square cubic inch, material."

The way I see it, when the bullet travels through dry sand, it allows the grains to sort of interlock, whereas when moist, they can slip out of the way more easily.

The same kind of thing might pertain with sand versus the tiny particles of clay.

Just guessin'.

Terry

[Jim147]

That sand trap should work pretty good to let you dig out the bullets and throw them in a flat rate box and send them to me to turn into boolits.

[Ben]

For just a personal range, I wouldn't expect any issues.

Yeah, I'm not doing any crazy stuff here. It's for running a couple of mags through the carry pistols for practice when I can't get to the range that week, initial rifle sight-in (I can get about 50 meters), stuff like that. The hill goes a good 20' up over the top of the berm, and I chose an area where the hill blocks off line of sight to the neighbors offset on the other side (400-500 yards away).

Paper and similar targets only. Steel would be fun, but my defensive pistol practice is 90% <7 yards, and even with rifle plinking farther off, I just get paranoid about potential ricochets, even if it's only a 2% chance. My club leaves tons of steel out for members, so I can get my steel jollies there.

My only safety concern at this point is the Bumpuses kids that moved in with their grandpa on the neighboring property. They just stuck a target stand out in their field and fire away, and it's at a place where a ricochet could reach me at my range.

[230RN]

That sand trap should work pretty good to let you dig out the bullets and throw them in a flat rate box and send them to me to turn into boolits.

I once had mathmares about how many times any given atom of lead might have traveled downrange and been recovered from my dirt berm backstop to make the trip again.

I'd say it nearly drove me crazy except I was borned crazy in the first place.

Terry 230RN