I removed the Ruger birdcage suppressor and installed the Miculek compensator on my 581 Series Mini-14 (16” barrel). I want to see what difference there is between the two in maintaining target and accuracy. The compensator came with a jam nut and the correct 1/2 - 28 thread. It is described as for the AR-15 rifle and is about twice as heavy as the birdcage. I wanted the compensator to seat on the end of the barrel and be turned so that the ports are in the correct position of narrow web up and tilted clockwise (from shooter) at about the 1:00 position. I used stainless steel shim stock at about 0.019’ thick to make a spacing washer. Now when the compensator is tightened, the barrel is tight inside of the compensator and is in the correct position. The Jam nut was also shimmed so that the flats are in the 12:00 and 6:00 positions. I made sure the hole in the washer/ship would clear the bullet no matter how it sits in the opening. Blue thread-locker was applied to the threads.
So, are you curious as to how it worked? The first thing I noticed is that there is a harsh rearward shockwave blast when a cartridge is fired. The birdcage didn’t do that. It hit me right in the face, I was surprised at that. No heat, just a blast. Perhaps having 3’x3’ Plexiglas blast shields on the left and right, 3’ away, caused it. The range is outdoors and has a roof overhead and an over-shoot barrier about 15 yards out from about 10’ bottom to 25’ at the top. So sound also bounces back from there. At 50 yards the bullet hits (groups of 3) were all 2-3” away at 4:00 from my previous center base-line groupings. Hits were within 1-1/2” apart. Sighting was done by a Millett Red-dot and the iron sights using weaver See-Thru mounting rings. There was little difference between the Red-dot and the iron sights groups.
The gun had almost no movement off of center after a shot. Wow! I adjusted both and the shots began to group at center again. However, as I shot more groups the spread between shots moved from about 1-1/2” to 3” then 4” and the groups wandered. Then I discovered the compensator had loosened and had turned almost 180 degrees. Not enough thread-locker I suppose. I did not notice any change in sound or recoil. By that time I had to leave.
Summary: the compensator settles the gun so there is nearly no movement after a shot. However, every shot pulls on the barrel and will spin the compensator if it is not secure, shot groupings will wander and general spacing will increase. Switching between the birdcage and compensator will require a re-sighting.
Next steps: I will add more shim and thread-locker so the compensator will tighten even more and not move. I will reshoot and post the results.

Trig

I have one of the Miculek brakes and it is much more accurate than the linear brake which came on the Mini. as in 1.5" at 100 instead of 3-4". Was going to see what the accuracy was with just the thread protector but the day I tried I was running out of time and couldn't even get on the target once I took the Miculek off. Did notice 3" muzzle rise shooting from a machine rest with the thread protector only, vs. no muzzle rise for the Miculek. With the Miculek on this particular rifle skinny 580 cut to 16 inches, there is a huge difference from the laser boresighter alignment to the point of impact at 100 yds. And there is nothing wrong with the boresighter either. I use it on my Target Mini, whose POI is within 2-3" of the borsighter aligned position.

I am planing to go to the outdoor range tomorrow to do some more experimentation with the Miculek equipped rifle. Mainly to check how it shoots in a glass bedded laminate stock it has been in, vs. the black synthetic, which I decided to move back to for weight savings and better balance. If I have time, once I get thought those tests, I may get to see how it shoots with just the thread protector ring vs. the Miculek now that I understand how much the POI shift is. I should be able to dial it right back in after popping off the muzzle brake. BTW, I had the same thing happen with groups going to hell when the Mucelik rotated without me figuring it out till I got home on an early trip to the range. After that trip, I put a bunch of blue locktite on it and it hasn't moved a bit during 4 trips to the range and about 350 rounds. I guess I should hope it comes off readily. Locktite looses about 2/3 of its strength at 300 degrees. Maybe the brake approaches that temp with continued shooting?

Totally agree about the noise and blast from the Miculek.. Definitely unpleasant, but it sure works good, and truth to tell, a 16" .223 is pretty loud to start with.

Muzzle brakes tend to send everything (gases/noise) back at the shooter. I have Shot 5.56 with a Yankee Hill Y-comp, bird cage FH and a Phantom FH. I must say the Y-comp is LOUDER than Heck. The Phantom work the best as far as sound and perceived recoil. I prefer a good FH for a defensive carbine such as the Mini...(so I don't flinch as much)...

Decided to make sure I could get the comp off before going to the range, which didn't happen yesterday - maybe Tuesday.. Anyway, decided to set up to shoot with thread protector only, first, and then put the compensator back on at the range instead of possibly having to wrestle with trying to get the brake off in the field. I put a wrench on the jam nut and a large screwdriver shaft through the gas holes in the compensator and applied torque and was surprised to find it felt "sticky" (best word I can come up with for it) but wasn't really tight. I'd put blue Loctite on it and tightened up the jam nut pretty good as mentioned earlier. The comp hadn't rotated but the Loctite had melted and failed. As per the previous posting, I hadn't done a lot of shooting and only 1 mag dump over the last few range trips. I noticed that gasses had leaked back some through the threads, I cleaned the carbon off the brake and its threads look OK. The threads on the stainless 580 barrel are in perfect shape.
I saw discussions elsewhere where folks recommended drilling out the first baffle in the Miculek as it serves no function other than creates a non ported chamber between the end of the barrel and that first baffle. Due to some system error I couldn't attach the photo even after multiple tries. Will attempt to add it to a new post.. In some guns with longer barrel threading it's possible that barrel end would seat against this first baffle, but unlikely it would index properly. Can't see it serves a purpose and I agree with the speculation that it is useless. I do think it contributes to leakage and loosening by creating an unnecessary pressure chamber between the end of the barrel and that first baffle. I am going to drill that first baffle out before putting the brake back on my rifle.

My second attempt at the Miculek compensator went well. I put 2 full drops of blue thread-locker on the threads. It didn't loosen. Accuracy? I don't believe that it made my groupings tighter, perhaps even a little wider. It does keep the gun pointed at the center of the target. It is much heavier than the birdcage.

Summary: For now I'm going to remove the compensator and use birdcage suppressor that came on the gun. The tradeoff of the harsh shock and sound isn't worth it on the range I go to. When I get a chance to shoot on open ground I will try it again.

Trig