I second Palmetto State Armory, I have used them many, many times. They put stripped lowers on sale frequently in the $50 range, simple to assemble, add your choice of flavor for uppers and good to go. As far as suppressing, subsonic rounds are a lot quieter than supersonics but even with those, there is a lot less muzzle blast and noise. I chose to go .30 rather than 5.56 suppressed because I like the 300 blk round, and I like to shoot Corbon subsonic 308 rounds in my model 700. Quiet, like a ninja! I also have a .22 LR suppressor that I put on a .22 cal AR and my Browning Buckmark pistol. Way too much fun.
Depends on the caliber.
The powder in a typical 300 BLK fully burns in a 9" barrel. A 5.56/.223 needs 15" or more which means you lose a lot more velocity with a short barrel. So a 5.56 pistol gives you a lot of noise and flash, but not that much performance. Make sure you have good ear protection, and you might want both plugs and muffs.
SBR is a little more controllable, comfortable to shoot because of the stock. Although the braces help with that problem some. Outside of room clearing and vehicle entry exit, either one is not much more handy than a 16" barrel carbine and do have some drawbacks incl muzzle flash, noise and reliability. But to each his own, they can be fun to play with and sometimes you just want something because you want it and that's reason enough.
Training is the way to go , I have been blessed by being surrounded by a group of friends that shared the same firearms passion that I have and we have (as a group ) brought in some top notch firearms experts to help us learn the right way to use our weapons. Not one of them told us to go through the trouble of getting a SBR or pistol for the training or defense. The best thing to focus on is accuracy and speed, with accuracy being #1. Knowing exactly where each round fired will hit every time and at whatever distance you are at is the most important. I have an AR pistol in 300 BLK I put together with a can but for serious use I will always grab my 16" carbine with simple and lightweight flashlight and aimpoint. That is a serious weapon, AR pistols are toys, (but fun). I'm not knocking your desire or right to have one but nothing will beat a simple 16" barreled or 14.5 barrel with welded on 1.5" flash suppressor for serious training or work and and won't be a pain the a** to get, carry, hold or license.
