Welcome to reloading!
I used to use the "stepped, more pointed" 9mm RN lead bullet (like the left bullet in the OP picture above) but now use more rounded and shorter RN bullet (like the right bullet in the OP picture above).
Why?
The stepped bullet with shorter bearing surface (part of the bullet that rides the rifling) has an inherent limit to how short the bullet can be loaded.
For some newer semi-auto pistols that require shorter OAL to feed/chamber more reliably, seating a stepped bullet deeper will push the shoulder below the case neck. The newer cast bullet shape with longer bearing surface and smoother transition to the shoulder allows shorter OAL yet more reliable feeding/chambering.
The longer bearing surface/larger bullet base also helps to seal the bullet with the barrel better to produce more consistent chamber pressure and reduce gas cutting/leading which translates to improved accuracy. Check this resource out for more in-depth information on cause of leading and prevention -
http://www.lasc.us/Fryxell_Book_Chapter_7_Leading.htm
patmetz, determining proper bullet diameter and OAL is crucial when shooting lead bullet to reduce/prevent leading and obtain accuracy. I also use Lee Classic Turret press with Pro Auto Disk powder measure and would suggest the following steps for a new pistol/bullet:
1. Determine the groove diameter of the barrel by slugging the barrel
2. Use lead bullet diameter sized .001" larger than the groove diameter of the barrel.
3. Determine the Max/Ideal OAL by using your pistol/barrel/magazine.
4. Using the Ideal OAL, conduct a full powder workup from start-to-max load data to determine accurate loads that reliably cycle the slide.
1. Determine the groove diameter of the barrel by slugging the barrel.
Determining the groove diameter of the barrel should be done
BEFORE purchasing lead bullets as the diameter of the bullets should be .001" larger than the groove diameter of the barrel.
Groove diameter is measured groove-to-groove of the rifling and often determined by slugging the barrel -
http://www.youtube.com/watch?v=CR_WiL8Dkgw
2. Use lead bullet diameter sized .001" larger than the groove diameter of the barrel.
Typical 9mm groove diameter is .355" but many factory barrels are oversized (.356"-.357"+) and will require larger sized lead bullets. If your barrel is .355", then use .356" sized lead bullets. If your barrel is .356", then use .357" sized lead bullets, and so on.
3. Determine the Max/Ideal OAL by using your pistol/barrel/magazine.
You do not need to use the OAL listed on published load data as often test barrel fixtures (and not real pistols) are used to measure chamber pressures. Using published OALs WILL NOT ensure reliable feeding/chambering of finished rounds in your pistols.
Determining OAL should not be a guessing game and I use the following process for semi-auto loads whenever I use a new bullet:
a) Make sure resized cases drop freely into the barrel chamber. If not, adjust the resizing die to ensure the cases are resized full-length and fall in freely into the chamber.
b) Determine Max OAL - Make a dummy round (no powder/primer) and perform the barrel drop test with the barrel out of the pistol starting with the SAAMI max OAL until the dummy round falls into the chamber freely with a "plonk" and spin without hitting the start of rifling. To determine the amount of taper crimp to return the flare back to flat, I usually add .020" to the diameter of the bullet (So for 9mm .355" diameter bullet, .375" taper crimp and for .356" bullet, .376" taper crimp). Note: Some headstamp case walls are thicker and you may need to use even less taper crimp by .001" (so for .355" bullet, .375"-.376" taper crimp and for .356" bullet, .376"-.377" taper crimp).
c) Next determine Ideal OAL - Load the Max OAL dummy round in the magazine and manually release the slide without riding the slide with your hand. Incrementally decrease the OAL until dummy round reliably feed/chamber. Depending on the pistol/barrel used, Ideal OAL that will work reliably will vary. If you are reloading for multiple pistols, use the Ideal OAL that will work reliably in all the pistols.
9mm cases headspace on the case neck edge/mouth and length of leade/start of rifling will determine the OAL of finished round and may vary barrel to barrel. Since case wall thickness will vary depending on headstamp (usually around .010"), adding .020" to the diameter of the bullet will either add flat taper crimp or slightly negative taper crimp shown below.
Note: Drawing not to scale
As to bulging of case and the "Coke bottle look" of finished rounds, this is normal for reloaded ammunition, especially when using larger diameter lead bullets. 9mm is a tapered case (the base of the case is larger than the case neck) and when the spent case is resized, the diameter of the case neck is reduced. When a bullet is seated, the neck tension of the case neck against the bullet will show as bulge at the base of the bullet. The bulge will be more prominent when using larger diameter lead bullets.
4. Using the Ideal OAL, conduct a full powder workup from start-to-max load data to determine accurate loads that reliably cycle the slide.
Once you determined the OAL that works well for your pistol/barrel/magazine, next you want to conduct a full powder workup.
Why?
Conducting a full powder workup will allow you to determine the precise powder charges (for the OAL you are using) that will start to reliably cycle the slide of your pistol. Once you have reliable slide cycling/spent case extraction, then you can focus on the accuracy trends of your shot groups to determine the most accurate powder charge loads (either target, full-power or both).
If I am using shorter OAL that seats the bullet base deeper in the case neck, I will often reduce the published start/max powder charges by .2-.3 gr. I will load 10 rounds of .1-.2 gr incremental charges and range test 3 shot groups at 7-10-15 yards. Typically, most powders will produce more accurate shot groups as the powder charges approach high-max load data. Faster burning powders like W231/HP-38 will often produce accurate shot groups even at mid-to-high range load data and I reserve these powder charges for lower velocity target loads.
I have outlined my load development of similar bullet nose shaped 125 gr RN and SWC bullets using Promo/W231/HP-38 powders on this thread -
http://www.thehighroad.org/showthrea...23#post8004823