I live in California. In many ways it is a wonderful place to live (or at least that is what I keep telling myself). The weather is awesome and… well, I am struggling to come up with anything else, but the weather is pretty nice.
Political climate here is a little bit tricky, especially if are a gun owner. As far as California political class goes, the residents of California are classified along these approximate lines (from most respectable to least respectable): Hollywood people (Harvey Weinstein et al), Sacramento politicians (finance by Harvey Weinstein et al), left wing academia (PhDs in basket weaving preferred), rapist and murders, non-violent felons, people who work for a living and, finally, gun owners. If you happen to be a gun owner, it does not matter what else you do. In other words, a PhD in nose picking does not redeem your sins if you happen to be a gun owner. The only exception to that is if you are a gun owner wealthy enough to lavishly donate to carious politicians’ re-election campaigns. If you do that, you can go out to the parking lot with a machine gun and mow down a bus full of nuns. Noone cares for as long as re-election checks keep coming in.
Ultimately, California is marching toward finally abolishing firearm ownership, but they can’t do it outright, so for now they seem satisfied with making it ever more difficult in a step-by-step manner via a bunch of regulations that are so spectacularly idiotic only a politician could come up with them.
One of them is the definition of an assault weapon. Not satisfied with the definition already on the books, California came up with their own ever changing definition. I am not going to into all the details, but basically, if you have a centerfire semi-auto rifle (like the ubiquitous AR-15) you have to be real careful with how you equip it. For example, if you have such a rifle with a detachable magazine and pistol grip, you are a felon. However, if you have a finned grip that does not allow you to wrap your thumb around the grip, you are a law abiding citizen (for now).
Basically, if you have a detachable magazine with any of these, you are a felon: pistol grip, collapsible stock, flash hider, bayonet mount. There may be more “evil” features, but these are the ones I remember.
To keep your build featureless, you have to either give up on a detachable magazine and separate upper and lower receivers to reload or make sure you do not have any other restricted items on your gun. Here is an example:
Most of these different options are reasonably well explored, but with muzzle devices it is not all clear.
We know that flash hiders are not allowed (all the birdcage A2 style devices, multi prong flashhiders, etc).
We know that simple muzzle brakes like the ones used on competition guns to cut down on muzzle rise are good to go.
I think we can be reasonably certain that linear compensators are fine as well. They do not do a whole lot to reduce recoil, but the re-route the sound forward so there is a little less muzzle blast to the side and quite a bit less back to the shooter. The JAL linear comp that is in the picture above is one of those. I generally like the muzzle devices from ARP since several tend to be very compact: http://www.ar15performance.com/muzzle_devices
The specific linear compensator I use is this one: http://www.ar15performance.com/inc/sdetail/2121/39188
Of the ones ARP sells, only JAL linear comp and SSB Shorty Brake can be used in California. The hybrid design of the Vortex Comp makes it illegal here.
One other linear compensator I have used is from Kaw Valley. It is a fair bit bigger than the JAL, but it works and many people like its aesthetics: https://www.kawvalleyprecision.com/KVP-Linear-Compensator-p/kvp-linear-blk.htm
As far as competition brakes go, I do not have too much experience with those. There are a couple that I have used and I still have one from Adams Arms:
It does provide for noticeably faster shot-to-shot speed even with a mild recoiling 5.56 chambered AR, but this thing is impressively loud. One thing to look for with muzzle brakes is where the vents are. If you ever shoot prone, you do not want any vents on the bottom of the brake or you will be breathing a lot of dust. Also, having the vents on the top and non on the bottom helps control muzzle rise.
There are obviously many other good designs out there. I am not up to speed on the latest ones since I do not shoot in competitions and I do not like loud muzzle blast.
I do recall trying Lantac Dragon and it was effective. The rest of muzzle devices I have experiemented with were flash hiders and hybrid brakes which are no longer allowed here in Commiefornia.