After getting some shaving with my S&W629 .44Mag, I wondered if partial-length resizing would yield improved accuracy. Same theory as partial neck-sizing bottleneck cases.



Has anyone here done it? With what results?



(Insertion might be more difficult and intuition tells me pressure might spike a little so reduced starting loads would be in order.)

Think about what you are asking...

The bullet is being shaved...

And are you going to mark each case with the chamber number it was fired from in the revolver?

I have done this for years. I have used variations on this theme and tested them with a Ransom Rest. Here are a rew things that you might consider.
1-what the previous fellow wrote makes a great deal of sense.
2-You will get maximum precision improvement (group size) by making certain that your bullets are the same size as or just 0.0005-0.001" over chamber mouth dimensions. This is especially true for lead, copper is a little more tolerant.
3-Do not oversize. If you oversize your cases, there are two things that will happen: you will lose concentricity of the two diameters and you will squeeze size a lead bullet and deform it as it seats, destroying accuracy.
4-If you can pick a bullet/case combo that needs no sizing at all--do it. Example: light loads with heavy brass and large diameter bullets. Decap without sizing, recap, charge the powder, seat the bullet, and crimp. Be careful, some combinations will allow the bullet to work backwards into the case this way: use a bullet with a crimping groove and crimp into the groove.
5-If you must have a death-grip on the bullet, as in loads with slow powders, size with your sizing die floating. By that I mean do not lock it down, just allow it to stay loose at the lock ring. Check regularly to see that it has not moved. That way the die will float and move, following the brass and self-align.
6-Dead square case mouths, with no chamfer, are a must. Use a Forster or Wilson case trimmer for best results. Any deviation in the dimensions of the case mouth will give you a crooked crimp. Do not chamfer or deburr; the outside burr will be knocked off by the sizer and the inside burr will be removed by the inside expander. Simply adjust the flare on the case mouth a little to seat the bullet without shaving.
7-Use a Redding benchrest type seater (with the adjustable dial) and a Redding Profile Crimp Die where possible. After 40+ years, they are the very best that I have ever seen.
8-Spend at least as much time shooting and learning as you do loading. Call your shots, practice your timing and technique. Get a friend to be your coach. Most of all, have fun. Geo.