I never have shot a AR pistol, but I hear they are LOUD. Is there any advantage of going with a 7" barrel vs a 10.5" barrel? Is one more reliable over the other?

Thanks in advance

One is 3.5" shorter than the other. Performnce-wise, longer is better.

The 10" will be better in every way but length.

I just recently built a pistol. I went with a 7.5" barrel. I thought about an 8"-8.5" barrel but I wanted it to be short and I got a good deal on my upper. I'm glad I didn't go any shorter and I'm also glad I didn't go any longer. Its so light and I have a feeling its going to be a good shooter. I have not shot it yet. I am told that it will be loud and shoot flames. I can't wait!

My thoughts on barrel length were as follows. I wanted a pistol that was short and would give me a feeling of what an SBR would be like. I still want an SBR. After getting this pistol and feeling it, it really makes me want an SBR. I kept asking myself why go with a 10" barrel? It isn't short enough and at that length I should just go with a rifle again. I wanted something I could tuck away in a backpack and into my car. It fits the bill just right. I knew the pro's and con's going into it and for me the con's of a shorter barrel didn't out weigh the pro's. Its quick to move around. Its light. Its going to be a lot of fun to shoot.

7.5" barrel with the Shockwave Blade.  Makes for a very compact pistol which shoots accurately and reliably from the cheek weld position.  All I need is a red dot and it's all set.  This is also my home defense weapon, using 45gr hollow points.  I'm sure it will be deafening in the house but IF I have to use it I am hoping no more than a couple rounds would be needed.  Its my favorite firearm, by far.

Now that is a nice looking pistol. I am also using mine as my home defense gun. That and my G19 or M&P 9mm. I placed my rifle away and the AR15 pistol has taken over as my HD gun.

Unless your talking 300 Blackout
nice thing about 10.5" is that it uses the carbine length gas system and makes it more "gentle"( in 5.56)
I really haven't noticed that much more on the loud scale. The muzzle blast is closer so it would be louder, but I use a flash can and it sends everything forward more.  Also use hearing protection so I don't notice it that much anyway.  With standard FH or Muzzle Break you will feel the concussion from the muzzle.
my $.02

I think it's pretty much a personal preference thing about how and in what configuration an AR pistol should be built by any owner. A lot of these pursuits aren't life and death. Still, I've always wondered why the late Pat Rogers in one of his last public speaking engagements discussing AR platform issues made the rather strong statement about any 5.56 AR15 less than 10.5" was silly...or words to that effect. I've read many discussions about AR barrel length performance, but I wish Rogers had further explained his statement. I guess it has something to do with velocity drop or such, but I would have liked to hear it from him.

I would imagine that Rogers' assessment had more to do with the loss of ballistic performance with barrels shorter than 10.5 and the shorter gas system required by the shorter barrels.  If the gun is mainly a fun issue to get the shortest barrel possible, then strict ballistic performance and/or combat application isn't a priority.  I'm sure Rogers usually spoke to AR issues in the arena of combat, LE, self-defense, and other more critical applications.  Unless it's your only 5.56 weapon and/or you're relying on it to be a critical defensive/offensive weapon, any barrel length is fine.  This isn't saying you can't kill something/someone with a super short barrel AR15...just probably not the best length for the job.

I took a couple of classes from Pat and followed him online for years.

He didn't hold gun games or range toys in high regard.

Wife's Diamondback 10" 556 will suck the air away from you right after the deafening blast.
IMO a flash can of some sort is a good idea on shorties.
After watching the fireball and feeling the blast...I'm building a 7" shorty.

$.02 - Can you really have too many toys? Life's short...

I would consider building it in 300 blk. I was out shooting a 16" 5.56 today and I have one of those steel triangles that flip when you hit them. XM193 barley flipped it at 50 yards and Tula just made it ring. I will have my 300 8" BLK built by this time next week and I'm sure it will flip that thing with no problem using 147gr Freedom Munitions ammo.

OP, the shorter barrel will reduce velocity and you will get more flash. Not that its a bad thing, its just a fact.

I have a 7.5 - 7.62x39, 8.5 - 300blk, 10.5 223 Wylde and like them all. Just put a linear brake on it. Short pistols are just more fun.

Also get a lighter profile barrel to reduce muzzle weight. My 300blk has a heavy profile and a steel barrel nut and weighs a lot more than I like.

I put away my AR carbine too, the pistol is so much better for in the house.  Easy to put on target and with it against your cheek, everywhere you move your head, the pistol goes with you.  I will eventually put a Primary Arms red dot on it as those turn on with movement, perfect for grabbing it and go.

Do you have a link to that red dot? I do want to add a red dot at some point. I really like the pistol AR.

When I checked the Primary Arms spec it did not state an auto on, but the Holosun, virtually the same design but with the battery mount hidden, does have auto on and adjustable auto off.

https://rover.ebay.com/rover/1/711-53200-19255-0/1?type=3&campId=5337559805&toolId=10001&customId=izgjtlj2r000zk8a00004&mpre=http://www.ebay.com%2Fitm%2F272521233068%3F_trksid%3Dp2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT



Also the TruGlo is an auto on except has external battery compartment.  Supposedly TryGlo, Holosun and Primary Arms red dots are made by the same company in China.

https://www.amazon.com/dp/B0125ME16O?tag=vglnk-c102-20 red dot sight&tag=vglnk-c102-20

I have never fired a 5.56 of any length inside a house. I would have to think even a 10.5" inside a house would be awful.

While I also do not have a 300 blackout, the fact that most powder is supposedly burned in first 6-7" or whatever means the concussion would be much less than a 5.56.

My thoughts are a short AR sucks inside a structure because its so loud.  It sucks outside a structure because of the poor ballistics.  I have a 10.5" pistol only because I can keep it loaded and ready inside my vehicle. If I could keep a loaded 870 or 16" AR15 in my vehicle I wouldnt have built it.

I have a 10.5" pistol. While wearing muffs, I don't notice the increased noise. But the other day I shot it under tree cover in a ravine with only ear plugs. It felt like I didn't even have the plugs. Maybe my plugs suck, or maybe I'm just a wimp lol Next time I'm using muffs.

I have not had that issue with a 16" barrel.

Wow, that chart actually makes a 7.5 look better than I thought. I had read some where that you'd get about a little over 400ft.lbs. muzzle energy out of a 7.5" barrel. According to that, using a bullet energy calculator, you'd get 668ft.lbs. pretty impressive really. People act like a 7.5" is just a toy, one time a guy posted that the ballistics are so bad it'd just be "a really expensive .22", those ballistics are over 200ft.lbs. more than 45acp. Look up ballistics of 22tcm and 5.7 FN. People think those are cool cartridges and they aren't even close to 5.56 from a 7.5" barrel.
I personally have built 2 7.5" ars. One used a bear creek arsenal barrel, a2 fsb and no name bcg, no name carbine buffer&spring. Ran 100%. Can't remember a single malfunction ever.
The other was a upper I bought from JSE. I think at the time it was advertised as a dpms kitty kat, but not sure if it is. 7.5" hbar, a3 upper, semi auto carrier, a2 fsb. Standard carbine buffer&spring. Ran 100%. No jam ever.
The benefit of a 7.5 is compactness, weight and looks dang cool!
Benefits of a 10.5 would be longer sight radius, more velocity, more handguard real estate.