I looked for about an hour on information about whether the guns i have would work for a first time 3 gun attendee. So ill just jump right it

I have

Remington 870 shotgun

XD 9 subcompact

AR15A2 (fixed handle as the upper, its the government model)

i don't want to buy any new guns if i don't have to, and don't expect to win the competition, i just want to get my foot in the door and wondered if these are adequate guns to start with. I know it would be preferable  to have a auto loading shotgun, full size pistol, and a flat top AR15, but these are all guns i have owned previously.

I look forward to reading any feedback or tips i may receive, and THANKS in advance all who respond.

Chase

You'll be fine.   Run what ya brung.  3gun is a blast

The only one of those that will look out of place is the AR...but no one should care, least of all you:  you're just getting started.

Run what you have to start. Then upgrade later. No need to drop a big wad of cash right from the start. If you can, try someone else's gear and learn what works for you before you buy. Take all gear advice with a grain of salt. What works for them may not work for you.

You'll be fine. If you don't have them already try to borrow a holster and mag pouches for the pistol and rifle and some shell carriers for the shotgun. Good luck.

Also find out which set of rules the club uses and familiarize yourself with them before you go. Some clubs require new shooters to participate in a quick safety brief/training session before their first match.

You'll get killed. These aren't even going to place you in the upper half. Totally wrong guns.

I can promise you that he is not planning on winning, but making his first show. The comradery at the matches is much better then a comment like that BadgeBunny.  You can shoot what you want.  Like the other helpful posts, buy as you can to upgrade your competition setup.

Because gear is the thing that'll be holding him back at his very first match.

OP, go shoot whatever you have. You'll have fun and if you stick with it you can worry about gear later.

absolutely run what you brung. My first match was shot with a carry handle DPMS, a walther p99, and a pistol grip 500. I did terribly but I had a safe and good time, and it got me hooked. I got to the point where I was running 100% full custom later but that was when I was trying to break into the national level. life gets in the way. Anyway, my actual advice:

shoot slowly and make hits
be safe
watch your muzzles
watch your thumb loading that 870 or you will rip it to pieces. Ask me how I know
don't spend a dime on anything but ammo before the match
Talk to established shooters
talk to the shooters who shoot like you would like to. they will let you try/borrow gear and explain how they like their stuff set up
don't wear a war belt with a knife on it. you don't need a knife and will look like a tool.

otherwise go have fun!

Don’t worry about gear, as long as you have a few mag holsters and a gun holster you will be fine. My first match I carried a dump pouch for my shotgun shells and grabbed from there.

Biggest thing to remember is have fun, be safe and remember to put the safety on when you put down your long guns.

I used a Winchester model 12 pump I bought from the pawn shop for $150 at my first 3gun, a G17 and an AR.

Go have fun watch and ask questions.

It's seriously addictive.

Shoot it and have a blast. Do your best and learn from it! There's no better feeling than outshooting the gear dudes with simple equipment. Let us know how you did.