I've owned this Model 41 for about four years. I grabbed it for $400 at a LGS, with a 7" barrel. It's an absolute tack driver, that will gobble up just about any ammo. It really likes Wolf Match.
Yesterday, while at my club, one of the older members came in with a white sock, and in it was a 5.5" barrel, with a Behlert rib on it. He was getting rid of some parts, and he asked me if I'd like to buy this one. I've been looking for a while with no real luck. We struck a deal, and I took it home. It has a some mild freckling just aft of the muzzle on both sides, but nothing that can't be handled. The bore is absolutely spotless.
It's very well balanced, much better than the 7" barrel, and I get the benefit of a long sight radius. I'll give it a shakeout on Saturday.
I was aware of the late Austin Behlert's work, but not of this type of modification. The sight extension is held on with a flat head hex screw, and very nicely done. The top of the barrel also is drilled and tapped for a scope mount, and I just might shop for a red dot for it. If anyone has any suggestions for a red dot, let me know.