Matt,
I think you're underestimating the .357's flatness and the red dot is going to severely limit it's abilities. Mine will shoot 1" groups at 100 yards and I don't have many doubts that yours will too.
A lot of people brag on Unique, but I think for my money I'd rather use 2400. Lee's Modern Reloading 2nd Edition says you can use 17.0 gr of 2400 with that 125 gr bullet. That will get you close to 2000 fps, even with the short barrel. I use the Remington Golden Saber, which is going to gain a little speed due to its bore rider design, plus it's a cheap bullet from Midway.
I think you need a scope when it's traveling that fast, which isn't going to do much to the portability/handiness compared to a red dot.
Mine didn't shoot worth a hoot until I floated the barrel and quit using anything but a taper crimp. A roll crimp isn't needed in a single shot and you can probably get more bullet pull with a taper crimp than a roll crimp.
Since I got a Lee carbide die set, I quit using anything else, even though I have 3 sets of RCBS steel dies. I use a Lee Classic Cast Iron Turret and put a separate crimping die in the fourth turret hole, so I can crimp in a separate step from bullet seating.
Mine also took quite a few rounds through it to break the barrel in. I shot it in and didn't even consider lapping it.
Try again and then give us a good report of your success!
