Doc,
That frame is not up to shooting a cartridge that can generate 36,000 PSI of chamber pressure.
Remember the 1917 was designed decades before the release of the First Magnum handgun cartridge.
Now if you wanted to make that revolver into a 44 Special that would be another story, the 44 Special has a SAAMI MAX Pressure of 15,500 PSI
As to your accuracy issues. are you using cast projectiles ? If so, are you using projectiles sized to your bore ? Lead need to match.
A switch to jacketed/plated/coated projectiles will probably increase your revolver's accuracy potential. Jacketed/plated/coated projectiles are much more forgiving on sizing issues
I sure wish I knew where chief38 was buying those Model 29s. I have never seen a Model 29 for sale in any condition for the cost of a barrel and cylinder.