I retired my Dirty Harry era M29-2 twenty or so years ago. It was a disappointment from the get go, with mediocre cast accuracy, leading in the forcing cone, a habit of unlocking the cylinder with full snort loads, a broken side plate screw, and an uncomfortable square butt grip frame. The cylinder throats were sloppy and the forcing cone would swallow an entire 45 acp bullet.
Then I brought it out of retirement briefly for an experiment with 0.434" plain base bullets, which I posted about elsewhere. The 0.434" bullets cured the leading problem, but required turning the case necks to chamber. I experimented with reaming the chambers to accept the fatter cartridges, but got in a hurry and botched the job. That was the end of the 44 magnum experiment. No tears were shed for the M29 because it had already been retired, anyway, and replaced with a Ruger Speed Six 357 that did everything I needed a packing pistol to do. The little Ruger is surprisingly accurate and has been 100% reliable despite being rode hard and put away wet.
But .... the Speed Six snubbie is no target gun, and my aging eyes can no longer shoot iron sights satisfactorily, so the Speed Six is poorly suited for accuracy testing of revolver bullets. A Freedom Arms is not in my budget, and for that matter, neither are most new Rugers.
So I thought "I've got that old piece of chit M29 laying around, why don't I do something with it?"
One problem with the M29-2, besides it's sloppy tolerances, is that the 44 mag is just too much cartridge for it. Smith and Wesson fans will disagree with me, but I came to that conclusion after putting thousands of rounds through it. It doesn't hold up to the recoil and it's not comfortable to shoot.
I believe the N frame is better suited for a lesser cartridge, and I considered re-configuring my M29 for 41 magnum. However, the 41 magnum with heavy cast bullets is nearly as powerful as the 44 magnum, so I was afraid that it might also be a little too much cartridge for the M29.
A rimmed 10mm magnum cartridge might be ideally suited for the M29, but that would be a 100% custom proposition, making it more expensive. I may yet build a 10mm cylinder & barrel for the M29, but I'm going to save that project for another day.
That leaves the humble 357 magnum. Used 357 cylinders are readily available for not a lot of money, and I had a chunk of 357 barrel left over from the Contender Carbine project.
A used cylinder was ordered from ebay and should arrive in a few days. I suspect that I will be dissatisfied with the accuracy of the factory cylinder, and may eventually make a homemade cylinder with tighter tolerances, but that'll take some time and perhaps more tooling, so the used factory cylinder gets the nod for now.
The barrel is ten groove, 20" twist, and 0.3475" bore. I think I only paid $15 - $20 for it at the time, though the ebay seller has since raised the price to $50. Apparently I never did measure its groove diameter -- they can vary quite a bit on 35/9mm caliber barrels, anywhere from 0.355" to 0.358". I'm tentatively aiming for an 8" barrel, because anything longer strikes me as more of a short rifle than a handgun. The barrel will be shrouded and fastened with a nut at the muzzle similar to a Dan Wesson. For today I merely turned the blank down to 0.680" and started making a barrel nut (actually 2 nuts, one being a spare). The nuts are threaded .670" - 36, same as the N-frame's barrel tenon.
I hope to get this project running in about 2 weeks. The only hard part should be making the shroud.