So talking to the wife about buying her a pistol and she said something about she much rather have a short AR-15 as I have for home defense.

I bought a 7.5 inch 300 BLK barrel for my lower than I bought stripped the same as hers. ( Just covering that it's legal.) She loved how small it was and she told me she felt she could manipulate the weapon better than the 16" barrel she is after all only 5'2 115 lb.

It's odd that she brings this up today after last night I bought a 10.5 barrel 223 for my pistol.

So looking for advice on what ammo to use? Will the standard 55gr and 62gr   I own be good enough? Or would a heavier bullet be better or lighter? I don't feel she will ever have to shoot it more than 100 yards and it's mostly going to be a home self-defense pistol.

Like to hear what you all have to think about ammo for this weapon. Also like to hear is there a better barrel length?

I do want something that can hit at 100 yards without having to train like crazy. Thanks for the help and advice!

55gr and 62gr should be fine

This is an example of 55 grain FMJ with a short barrel:  https://www.youtube.com/watch?v=4V_jGwXfkXA
Here's a 62 grain HP at 3:15 https://www.youtube.com/watch?v=P9hfyH-aoL4
75 and 77 grain bthp's out of a short barrel are quite a bit more devistating: https://www.youtube.com/watch?v=bv-zpVO8dJE
The 75 and 77 grain bullets will get you what your looking for in a HD situation better than the 55's and 62's IMO, but that's just me.

My suggestion would be using bulk 55gr/62gr for practice and selecting a quality 75gr or 77gr load for defense. Using a defense load for training/practice is either going to vastly increase the cost to shoot... or, more likely, vastly decrease the amount of practice you or your wife will be doing.

Cheap heavy soft points are as good as 30-06 hunting rounds according to an article written by a man who helped cull 105 white tails using different rifle rounds.
The only stand out from others was .243 Winchester rounds.

I'd think performance on white tail would translate well in comparison to self defense use.

I like anything 64 grain or heavier for my shorties. Gold Dot 75 grain bonded pills are nice as well as 75 grain IMI OTM's & my favorite the 77 grain Fiocchi OTM's... all 3 loads hit hard, the last two non-bonded projectiles that snow a target with fragments. From across room to across front yard distances just about an 50, 55, or 62grain ammo that reliably cycles will most certainly do though OP. I'd focus on 100% cycling reliability first, then your favorite bonded or OTM heavy load and being able to hit quickly what you are aiming at and use what works for your rig and accuracy.

I really wish I could have the chance to take these out and try them out first but there is only one range near me and I don't know the secret hand shake that will allow me to get in. The other ranges are 40+ miles away at infected towns/cities so want to stay away from them.

Yes it sucks I have lived in Texas since 2016 and have not lived in one town that has a range that you don't need to know someone who knows someone or other towns that just did not have one like Eagle Pass when I asked around there I was told by Hispanic people just shoot across the river! It's a border town.

Like to find a range near me but it's no that popular because most people around here have friends who own ranches and can shoot there.

Where at in Texas are you?

I'm surprised that no company, as far as I know, has come out with an ammo line specifically for short barrelled ARs(pistols/pdws). Seems like there is an awfully big marketing opportunity out there that is being missed.

https://www.hornady.com/ammunition/rifle/5.56-nato-75-gr-interlock-hd-sbr-black#

Ok, that's one!

Why do you suppose they tested ammo for a SBR in a 20" barrel?

MV looks pretty slow.  IMI 77 grain Razor Core is faster than this.

MK318 is my choice.

Expands down to 1900fps, though be aware that it does show a tendency to over penetrate.

Should have pretty close poa/poi as m855 green tip for training.

For range shooting, i have had excellent results with standard green tip 62gr.  This is out of a PSA 10.5 (with flash can) and H buffer (doesn't matter, but still); I am a sucky shooter, but had no problem keeping 1-2moa the whole time.

Big spring TX.

My 10.5" (1:7) pistol AR is my son's (11 yrs) favorite firearm to shoot. When we are at the range he mostly shoots 62gr .223 rounds from Aquila. No need for 5.56 and I'm usually standing over him so the reduced muzzle blast from .223 is nice. I have a compensator on the muzzle so the blast is mostly up. Iron sights only so I mostly shoot this at 100 yards or less.

For HD or when I carry in my truck I load the Hornady .223 Remington 73 gr FTX Critical Defense round. There is a similar soft-nosed 62 gr hunting round that works similarly. Here again considering the possible distances I'd need to engage targets at, the .223 works just fine. Also in HD, lights out and probably no hearing protection, the reduced muzzle flash, recoil and report of the .223 round will be easier on the shooter.

I do keep a mag of M855 handy though, JIC i need to go through something ;-)