I checked and measured my 696 and my model 69 and there is no way I would ream a model 69 L frame 44 magnum cylinder to 45 colt and fire any of my 45 colt loads in it. Most of my loads are in the 23,000psi range.

aciera I will be interested in your results also. On a light 45 colt why not start with a 325 and use a 45 colt cylinder? I also like tight 45 colt chambers with .452 throats and got most of my colt cylinders by reaming 44 mag cylinders

But, I do not see why anyone would believe an L frame would not handle 41 mags when the factory produces them in 44 mag. I would go with a 69 frame as it uses a bigger barrel shank than the 696 or 686 frames. Just turn a 41 barrel blank to fit the frame and sleeve. You would have to make the cylinder from the ground up unless you could somehow get S&W to let you have a 5 shot blank or a complete blank.