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In short...I need to build a exterior wooden support structure that can hold a sand filled box 3'tall x 4' wide x 13" deep...weighing roughly 1400lbs.

The support structure needs to be at least 1 foot wider & longer and stand approximately 3 feet tall. Making the entire combined height 6 feet tall. I'm not sure what dimensions wood to use to support that weight nor how to design it.

This supporting structure will be sitting on the ground. I want it to be "temporary". As I do not want a permanent concrete pad for ground support. I do realize the problem with that idea. If there is a way to get around making a permanent base, that would be ideal.

I thought about using railroad ties and as a ground level base to help with elemental degradation, but have no easy way to cut something that thick.

Any ideas will be so much appreciated!

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  • Since this is a shooting backstop, two questions immediately spring to mind. This is intended to be open-fronted yes, so the sand is banked up towards the back? Are you sure that quantity of sand is enough to stop what you'll be shooting?
    – Graphus
    May 19 at 7:19
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    I made a smaller mock up design - 12" tall x 12" wide x 13" deep open topped - to test if depth would be an issue. At 5 yards - 115 FMJ grain 9mm and 55 grain M193 5.56 did not penetrate the back of the box.
    – Slickgsxr5
    May 19 at 11:27
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    Thought about using shredded rubber as a filler but with the amount of airy negative space didnt leave me feeling too confident it would contain the lead core and would ultimately defeat the purpose of the box itself.
    – Slickgsxr5
    May 19 at 11:32
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    no it is not intended to be open. The box is framed with 2x4s with 1/2" plywood sides and top, 3/4" plywood front and back. The strike face, along with 3/4" plywood will have a sheet of self healing rubber to seal and hold the sand back as holes are made in the wood face. Sand is an excellent medium when contained to prevent ricochet as well as contain the lead core or spalling from contaminating the ground or areas within the backstop. Yes its plenty deep for what I'm dealing with.
    – Slickgsxr5
    May 19 at 12:03
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    As an FYI - a Sawzall™-type saw equipped with a long blade should make easy work of a railroad tie, should you need to cut one for this or future projects. If necessary, you could probably rent one for just a few bucks for a 4-hour rental.
    – FreeMan
    May 19 at 12:32
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I would frame this with 4x4 corner columns extending up the full 6' height. I would frame the elevated floor with 2x6 joists at 16" oc. max. The deck can be 3/4" plywood. In essence your are building a very small house frame. You can make the 13" sides with the remains of the plywood and secure the panels at a the top to a 2x4 top plate and studs at 16" oc. To keep it from racking use "X" diagonal 1x3 cross braces secured to the 4x4s from floor level to grade. Since it is temporary, you can rest the columns on a couple concrete block slabs 2"+/- thick. I also recommend having a means of draining the plywood floor and using a plastic sheet to keep any wet sand from directly contacting the wood assembly.

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  • Pay extra for pressure-treated lumber or expect to have to build this again in only a few years. Also, they sell 4x4 or 6x6 concrete feet for this exact purpose.
    – jdv
    May 19 at 16:01

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