Here is how I built my cart Please feel free to use any of my ides. I have also placed links for some of the items I used.
I have built a cart in the past. I have also seen and looked carefuly at many carts at major 3-Gun matchs and smaller matches, After looking I came up with a list of things I wanted in a cart and things I did not want.

1- It had to be able to carry enough "stuff" for at least one day at the MGM Ironman match.

2- Almost without exeption every match has had one of two things: Rain or Sun

Rain: About half of the cart I have seen addressed this problem by being able to cary the gun in it's case. this will protect it from the rain. Like most of the carts made from a wagon, The allow you to put the gun in its case and cart it around. All of the other carts leave the gun out for the rain to get to it. Most notably are the carts that are made out of a hand truck or the "Rugged Gear" cart.
Sun: When it is sunny it is dusty. I remember going to the Ironman one year and I had my guns in a Hand truck style cart. With the guns exposed and with the wind the guns got covered with dirt. That was a bad idea. On another occation I went to Elko NV in Aug for a match and it was hot and dusty, This time I keept my guns in the case and just draged everthing around. This tought me two thing, THATS A LOT OF WORK and It keept the guns clean. When I got home the guns looked like I had only done target pratice at an indoor range with them not a match in the middle of the Nevada desert.
The cart has to protect the guns when your not shooting.

3- When you go to a match you do not always shoot all three guns on every stage so I want to be able to put my pistol mags, Rifle mags, shot shell holders, ect ...  in a case when I am not using them.

4- I want all my ammo in a case like I do when I shoot a pistol match. In a 3-gum match you have alot more ammo that you are changing in and out.

5- A small cooler would be great to put water or gatoraid in so it would stay cool at least part of the day in 95 degree heat.

6- Some way to carry , Extra choke tubes, oil, cleaning rod, Ect. All that extra stuff you want to have close at hand so that you do not have to walk all the way back to the truck when you are on the stage that is the farthest away from your truck.

7- No way am I going to put the muzzle of my $1500 JP rifle or any other gun into a "hole" to support the front of it. All you need is a small nick or ding on the crown of a gun and that barrel is done. When I saw the "Rugged Gear" cart doing that I thought "What a dumb idea I do not want that in my cart."
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