I have 10 of the Muller chokes for my Blasers and really like them. None of them purchased new though, got most from classifieds here and ShotgunWorld. Patterns compared to my stock Blaser chokes are more even and they are easy to clean.
I shot a Krieghoff KX-6 with the Muller U3. Mostly ink spots (18 of 22). Excellent, but I wasn't certain whether it was the choke or the gun itself.
This weekend I tried a friend's Beretta 682 Gold e unsingle. Started with the regular flush Beretta chokes and did as expected, 23. I installed a Muller U3 that was in his case. Similar score, but more smoke and fewer chips. Subjective from my personal perspective.
Conclusive testing? Not by a long shot. They look cool and seem to work fine - at least in my limited trials. The only shortcoming I see is the inability to pick up a magnet pad with the in the barrel. If I get any of the Muller's I'll probably go back to holding the gun between shots or resting it on my toe.
I shoot Muller chokes in my Browning INV+ and havn't seen any problems but if I do I'll post here. I wonder if the problems some see are specific to certain gun types or maintenance related. There are a lot of people shooting them so I don't think the problems are inherent to the design. Joe
They have a very enthusiastic support group that we derisively referred to as the "Muller Mafia" early on. They now call themselves by that name as a badge of honor and aggressively defend their choke of choice to the death in spite of all evidence of failures due to possible faulty design/materials. The idea that someone can tell the difference between Mullers and a pair of similar sized titanium chokes at the end of 4 pound barrels is whimsey at best. That guy P. T. Barnum must have known some Trap and Sporting Clays shooters 'cause we will try/believe anything regardless as to how improbable logic says it is.
The psychology has to be that since I've spent this much money for these things they must be really good and I'll be damned if I'll admit I'm a sucker. Well, I personally fell for the HiDefSpex BS so I can't laugh at anyone else! They turned out to be OK glasses for driving and the beach (until I lost them in the surf) albeit expensive and no better than the Decot, Ranger or Post4 that I had.