Penetration?

[TAJ45]

I need an idea how deep my sand bunker needs to be to contain tgt bullets pushed to 3k fps/284W, 308 LC Match, besides 6XC et al in that neighborhood @ 3300 tops at muzzle.
My first bunker is 260 and is 6-7' deep.
I don't think the 700 yd will be a prob between velocity loss and the entry trajectory. In hindsight, it didn't need to be as deep as I made it. Oh well.
I can always build a test box, baffle it with skinny Luan, fill w sand to see how far things progress but don't need another project. Still need to construct deck and bench tops etc. I'd like to do some shooting before year's end...
Anyone have any experience or knowledge here?

 

[people]

It depends on your sand. Fine sand you need more very course sand you need less. Then if the sand gets wet that will make a difference also.

What I did for my berm was basically filled the middle with big rocks.

ddddddrrrdddddd
ddddddrrrdddddd
ddddddrrrdddddd
ddddddrrrdddddd
ddddddrrrdddddd

d = dirt
r = rock

Nothing makes it past the rocks. Most bullets never make it to the rocks but nothing makes it past them.

 

[TAJ45]

It depends on your sand. Fine sand you need more very course sand you need less. Then if the sand gets wet that will make a difference also.

What I did for my berm was basically filled the middle with big rocks.

ddddddrrrdddddd
ddddddrrrdddddd
ddddddrrrdddddd
ddddddrrrdddddd
ddddddrrrdddddd

d = dirt
r = rock

Nothing makes it past the rocks. Most bullets never make it to the rocks but nothing makes it past them.

Very interesting. I can see the wisdom in that. Thanks

 

[4xforfun]

Build it 10 - 15 feet high and don't worry about a thing!!

 

[TAJ45]

Build it 10 - 15 feet high and don't worry about a thing!!

Thanks for the reply 4by but that only addresses frontal area....I need penetration info.
I built a decent sized log cabin with power poles and have filled it with sand, dirty sand too. More concerned with the point blank structure 260 yds out.

 

[4xforfun]

Thanks for the reply 4by but that only addresses frontal area....I need penetration info.
I built a decent sized log cabin with power poles and have filled it with sand, dirty sand too. More concerned with the point blank structure 260 yds out.

Sorry, but a 15 foot high berm will be at lest 30 feet thick at the base. 20 - 30 feet thick should stop anything you can throw at it.

...or are you talking about building a wood "box"?

 

[Sniper338]

we got a deep freezer at the ranch full of sand... stick targets on it with magnets... havent had a bullet go through yet... so 3 to 4 ft thick stops most everything... fyi

 

[okie]

big skidder, loader or tractor tires filled with sand or gravel will last a long time. stack em up, bolt em together or drive long t posts around them.

 

[dolek]

we got a deep freezer at the ranch full of sand... stick targets on it with magnets... havent had a bullet go through yet... so 3 to 4 ft thick stops most everything... fyi

I need to give that a try,small and easy to fill. Thanks for the idea...not sure why I never gave that a thought. I use oild barrels but something with flat sides would be better.

 

[mr45man]

Just for fun, fill a 5 gal.plastic bucket with sand and shoot it at 100 y.
Let us know if has an exit hole.

 

[TAJ45]

It depends on your sand. Fine sand you need more very course sand you need less. Then if the sand gets wet that will make a difference also.

What I did for my berm was basically filled the middle with big rocks.

ddddddrrrdddddd
ddddddrrrdddddd
ddddddrrrdddddd
ddddddrrrdddddd
ddddddrrrdddddd

d = dirt
r = rock

Nothing makes it past the rocks. Most bullets never make it to the rocks but nothing makes it past them.

Abt how deep is the sand before the rocks, range and calibers. I can

Sorry, but a 15 foot high berm will be at lest 30 feet thick at the base. 20 - 30 feet thick should stop anything you can throw at it.

...or are you talking about building a wood "box"?

Boxes are built...kinda. The 700 has three sides, awaiting the back wall. The 260 has two walls up, sand in and ready to augur in the holes for the side and rear retainer walls.
FYI, I had always heard 3-1 ratio of hgt to base. Upon checking I found that dirt will pour to an angle of 30° -45°, depending on composition so 3-1 = nearly 35° when I trigged it out. Sand, salt sugar were similar but I forget now.
With the poles being free and my loader tractor, JD 955 only reaching 6ft with bucket flat, not dumping, it was much cheaper to avoid the $200 avg for 20 tons per load. Funny how large it looked in the pile till I started pushing it against the walls....

Freezer idea is great.

 

[alinwa]

It depends on your sand. Fine sand you need more very course sand you need less. Then if the sand gets wet that will make a difference also.

What I did for my berm was basically filled the middle with big rocks.

ddddddrrrdddddd
ddddddrrrdddddd
ddddddrrrdddddd
ddddddrrrdddddd
ddddddrrrdddddd

d = dirt
r = rock

Nothing makes it past the rocks. Most bullets never make it to the rocks but nothing makes it past them.

This is beautiful...... I've owned and been party to a bunch of private and public ranges with bullet stops from dirt to sand to gravel ground up tires to stacks of/layers of wood and they all have problems with "cavitation" which means that even a 22LR can tunnel a long way over time and thousands of rounds. A 50BMG can tunnel thru 12ft of dirt in one shot, a 6PPC might take thousands of rounds and normally the medium caves in to fill the hole BUT, I've seen some weird stuff, like a pellet rifle guy shooting his neighbors house through a block wall and a couple ft of dirt outside.....

The pile of sand with rocks in it smacks of genius.

Thank You!

 

[people]

Abt how deep is the sand before the rocks, range and calibers. I can

Mine is set up with a few feet infront of the rocks the rocks are about a foot thick. Give or take a little. Most of it is just field stone with some 1.5 to 2" rock that one would use for a driveway. Then a couple feet of dirt behind the rocks. The front and back started as railroad ties. The front I have just added a few boards when dirt is starting to come out. We have shot everything into it I have and a few friends have shot a thousands of 50BMG into it.



I also have a big berm that is built the same way but the dirt is piled up into a big hill and not held into position.

 

[ebb]

Years ago I had a 5 gallon bucket on the job site full of a local fill called shellrock. At ten feet never could get a 150 grain 30-06 to exit. The shells and rock grind the bullet to pieces

 

[datp]

A Hesco (wire screened basket with felt like material to keep the sand inside) barrier is approximately 4ftsq and will stop most everything thrown at it including 107mm rockets, RPG 7and9 etc.

 

[Outrider27]

Around here (south central PA) they sell a grade of gravel called "crusher waste" - it's cheaper because it hasn't been sifted to remove anything but the big stuff (over an inch or a bit less), so it still has the fines (the powder portion) in it. We use a pile of that stuff about 5 feet front to back at the impact height for everything from .22RF to 338 Lapua mag and nothing gets through it. Plus the fines keep it stable and snug. Just another option.

 

[savagedasher]

Just take a arrow . It will zip right through a bucket of sand . Does the same with water . Larry

 

[alinwa]

Back to the rocks for a minute......

IMO the single biggest thing is to get something that's not prone to what I called "cavitation." What I mean is, all of the media mentioned will stop a bullet, or 10 or 20 or even a thousand but the problem occurs with ACCURATE rifles and over time. I have a tendency to use acoustic targets or just to keep tacking up new sheets over the same area and before I know it I've pumped thousands of rounds into this same area. And I never seem to have time to go stir the media enough. A pistol or casual target doesn't have this problem as the bullet impacts are scattered, thereby constantly stirring the pile.

I've never blown through in a dangerous fashion, YET, but I have occasionally run a hunk of rebar into the hole to find a cavity a couple feet deep in both dirt and sand. Whereupon I'll reach out with the backhoe or even climb up with a rock bar and shake/stamp the pile to jiggle the hole back full.

This gives me pause.

Especially since I've been involved with a dozen underground and/or covered ranges set up in town, in subdivisions and in tight quarters. I've spent time with steel plates (not perfect, ask the guy at XXXX bulletmakers range where he shot hisself in the leg with a 223 in the underground company facility) and trust me, the cavitation thing can be a problem. Many of the public or high-volume places run water into the pile "as needed" (you gotta' ask yourself, "HOW OFTEN?? and How Much?") in an attempt to wash sand back down into the cavities.... The downside of course is that wet sand cavitates worse, it's a vicious circle.

So here's where I see the real value in the rocks.....

My next indoor backstop experiment will be SAND, something flowable, and I'ma stuff those rocks in there so hopefully if a cavity forms back to the rocks, the bullets hitting the rocks will SHAKE THE PILE! Smack the rock a couple times and it (might? should? WILL?) jiggle the pile enough to shake sand back into the cavity.

Therein lies the "genius" I referred to earlier. YES, the rocks will stop bullets, but even more importantly I'd like to believe they'll solve the cavitation problem..... I'm going to place them "loosely" in the sand, with space between them so's they can shift a liddle.... kinda' stagger them around to make a "wall" but in 3-D where a mouse could tunnel around them but a bullet will always hit a rock if the cavity reaches deep enough.

Anyway, THANK YOU for a possible solution to a problem that's plagued me for 30yrs.

 

[savagedasher]

The military use sand bags. for a reason.
Larry

 

[pikespeakgoat]

Here is a link to a pretty good read, Range Design Criteria from DOE,contains some info on "thickness of material for positive protection":
https://energy.gov/sites/prod/files/2013/05/f1/Range_Design_Criteria.pdf