.41 Mag Accuracy
T/C Nimrod,
My accuracy with a 14" factory .41 Mag barrel finally got down to about 1 1/8" to 1 1/4" at 100 yards (although, I have to say that my .41 GNR #2 is currently shooting about half that - I wouldn't complete discount a rechamber if I were you). I believe the hollow point pistol bullets I shoot are more prone to be affected by the physics of flight much more quickly than pointed designs (i.e., accuracy at 100 yards is much more adversely affected than a pointed design even though accuracy was good/great at 50 yards). Hollow point pistol bullets were never really designed for the speeds and distances we use them at these days.
Nevertheless and the hollow point pistol bullet design notwithstanding, I had good luck with the Sierra 170's and 210's. My chronographed speeds for the 170's were in the 1,950 fps range and the 210's got about 1,825 fps. I used H110/W296 (they are the same powder according to Phil Hodgdon) with large magnum pistol primers and did not crimp. I'm sure my carbide sizing die had something to do with that as it sized quite small, similar to what a small base die might do for a bottle-necked cartridge case.
Here's a tip on bullet seating, it takes a little extra time, but you can get very fast at it and it helps me a lot whether I am seating straight wall or bottle-necked cartridge bullets (an index mark helps here, but is not mandatory). When seating your bullets to the selected depth, only seat about a third of the bullet's depth and stop - rotate the case about one third of its circumference - seat another third of the selected bullet depth - again rotate the case about one third of its circumference - seat the last third of the bullet's depth. I have had excellent luck with reducing runout due to seating errors this way and you can do it very quickly with a little practice. You will quickly develop a feel for it.
If you are throwing powder charges, you may try checking the weight more often or weighing each charge individually if it comes to that (powder weights have been known to vary for a variety of reasons when they come out of powder measures, so a check with a good scale can't hurt). You may also want to try some Hodgdon Lil Gun powder, I've had some good preliminary results with it in straight-walled cases and velocities are very good.
Assuming that the mechanical part of the reloading process is in good order and you have deburred your flash holes and checked for uniform diameters of those flash holes, if powder charges are correct as measured, then I believe your only realistic options are bullet seating depth and bullet selection. What type of bullet is being used and how far off the lands it is seated will be the determining factor in how well you can get your barrel to shoot. You may want to have an experienced and knowledgable gunsmith check the alignment of your chamber and throat to the bore itself. Again, not to harp too much on case indexing, but accuracy problems stemming from a bad chamber/throat alignment to the bore can generally be greating improved by indexing your cases and using a uniform method to place the case into the chamber - really, you will be amazed at how much accuracy can improve by doing this.
Good luck with your efforts - let us know how your project goes!
Javelina