Hi everyone, I am looking for some guidance from those more experienced than myself.

I only own one AR, and Daniel Defense ddm4 v11. I love it and am looking to build my next one. I was going to build an SBR but with the wait times right now with the ATF, I have decided to build a pistol and convert it into an SBR later down the road.

My budget is around 2000 for just the pistol. I already have the optics. I want it in 5.56.

I am wanting to go as light weight as possible as well as sturdy as possible so that it can be thrown in the back of a truck and beat up without having to worry. I know that strength and weight are usually at odds, but I wanted to see what could be done. It is mostly going to be a range toy, truck gun, and steel shooting gun at the ranch.

I was looking at information and it seems that a 10.5" barrel is recommended to get the best ballistics out of 223. So is going shorter than that usually frowned upon?

Sorry for such an open ended post, I am just looking for some help and ideas on what you would build if you had this budget. Thank you everyone in advance, I am really looking forward to putting this together!

There are few reasons for not going below 10.5"

1.most suppressor manufactures state 10.3-10.5" is the minimum length they will warranty parts of the suppressor.
2. below 10.3" 5.56mm/.223 starts to run into reliability issues, not saying you can buy one shorter, but you may have to play with it to get it to run, and even then you may have problems with certain brands of ammo.
3. .223/5.56 becomes pretty anemic below 10.3". It was designed to go fast, and short barrels lower the energy, plus the bullets won't fragment, expand, or yaw below a certain speed, 2500fps but don't quote me on that. Expansion will be bullet specific but again most were designed to hit flesh at a certain speed.

As far as best ballastics I would recommend a 20-24" barrel, but 10.3" would be the minimum in anything more than a range toy.

If you want to go shorter than 10.3" I would suggest another caliber, 300blk, 6.8SPC etc....

I own different AR uppers. 16", 12" 10.5" and two 8.5". The 8.5" uppers, they're just fun/noise makers. Definitely need some tweaking in order for them to run reliably. Usually that's getting a real heavy buffer and buffer spring also an extractor upgrade(o ring and spring). Shorter guns wear out parts faster so just be prepared to have frequent maintenance. Its not that bad really. Besides you'll be keeping the AR parts industry alive and well. LOL!!!
As for defense loads, pick a SP or HP round, and test them out and see which one mushrooms more. FMJs for the range. Have fun with your AR, don't let the nay sayers get you down. Besides, no one wants to get hit with a .223/5.56 bullet of any kind, regardless if it fragments, shrooms or not. Seriously man.

Sub 10.5 inch barrels is where BLK shines

and 9mm even shorter than that