Only thing I will add here is that the port angle on my PK brakes is NOT as aggressive as the Muscle brake which is set at 35 degrees. In fact my ports are set at 30 degrees so what has been said is not correct. My PK brakes do not have a more aggressive back rake angle on the ports, in fact they are less aggressive.
As far as muzzle blast comparision, I find this a little interesting. I designed my PK with larger port volume for the specific purpose of slowing the escaping muzzle gas which greatly reduces the intensity of the muzzle blast. This also reduces the brakes effectiveness at reducing felt recoil.
To counter that, I made the brakes a wide slab design to increase, dramatically increase the surface area of the parition walls in my PK brakes. The wide slab design also dramtically focuses the direction of the escaping muzzle gas which, to the shooter offers a much wider protection cone from the muzzle blast. It is more directionally focused to the sides so if your next to a PK, you will get lit up but if your behind one, they are much less obnoxious they any other parition style brake I have tested including the one being talked about.
My slim version is much smaller in diameter and looks VERY similiar to the Muscle, much more so then the standard PK but I am certainly not saying they are the same as there are internal features to the PK that are not in the Muscle and that makes them very different.
On big handguns I have also tested head to head pretty much every brake out there against my PK brakes. I have never found one that compared anywhere near to my big 5 port PK which was designed for the 408 CT based wildcats in rifles but works very well in very large handguns, in fact with my 338 AX. We can drive a 300 gr SMK to 2700 fps or even more and use rifle scopes with full field of view. For handguns I machine reverse "V" ports on the first three partitions for muzzle jump control which is not needed on my big rifles.
The only reason I made this post was not to compare the two brakes, only to offer correct information concerning my PK brakes which I did not feel was being protrayed accurately and I felt it should be to offer a fair discription of my brake first hand.
The Muscle brake is a fine brake, the PK brake is a fine brake, both greatly reduce recoil, both are loud, any brake that is effective at reducing recoil dramatically will be loud. To say one is any quieter then another is very hard for me to swallow as I would like to know how this is measured. I would dare say I have tested as many or more different style muzzle brakes
as anyone and in all honesty, I have never seen much difference in the "Loudness" of any of the muzzle brakes. Only difference i have noticed is the "Slap" on the forhead and my PK in its wide standard design is as good as any at greatly reducing this slap from the muzzle blast.
Do not wish to start a debate and have no desire to add anymore to this post as its not mine, only purpose was to offer accurate information on my Painkiller muzzle brakes which was not being accurately discribed.
I wish only the best luck to anyone else making fine products which all of these are.