The 38 caliber ammunition is a rimmed revolver case dating back to the late 1800s. Currently the most common of those are the 38 Special, and the 357 Magnum. Occasionally you will hear 38 Special bullets called .38 S&W, however, those are not the same round and are not interchangable. Over the years, the 38 was well known as the sidearm of most US police forces, until superseded by the 9mm and 40.
The 38 and 357 Magnum share the same bullets, a .357 diameter and a .358 lead bullet diameter is not uncommon. Bullet weights vary from 100 grains up to 180 grains and are available in mostly copper although lead bullets are extremely common. Another point to consider for readers, '38 bullets' are projectile tips or bullet heads, they can't just be put into a gun and fired. They are one of the four required components necessary to make a 'live' cartridge (ammunition). So insure you are really shopping for what you expect the product to do, if you want 'ready to fire' then you are looking for 'ammo' or 'ammunition'.
Common projectile tips are Round Nose (RN) and Hollow Points (HP), with many variations on each. For example, Berry's Bullets manufactures both a Target Hollow Point (THP) and a Hybrid Hollow Point (HHP)). Hornady manufactures an eXtreme Terminal Performance (XTP) and a Hornady Action Pistol (HAP). For self defense and small hunting, a Hollow Point bullet is preferable for expansion and knockdown. For plinkers, however, the 38 reloader should consider a plated bullet such as Berrys or a lead bullet which works well and gives you the best bang for your buck. Literally.
Slower burning powder works well with 38 caliber bullets because of their low to medium velocity (900 - 1,200 fps). Tightgroup, CleanShot and CFE Pistol powders are just a few that reloaders use with these bullets. However, remember to ALWAYS follow your data guide and stay within the standards listed and under the SAAMI maximum pressures when reloading 38 special bullets. Never seat the bullet head (projectile) deeper than recommended as that will increase the presures.
When shopping for 38 Special brass, Once Fired brass is a cheaper alternative to new cases so should be considered for reloading. If you are not an experienced reloader, you should read Once Fired Brass: The Beginners' Guide to Reloading.
Overall Length (OAL) may vary slightly when doing reloading. It's a good idea to load only a handful before safely checking them in your weapon. You don't want to be caught at the range with lots of pretty cartridges only to find out they won't chamber! Below are the items related to reloading 38 and 357 Magnums, and are shown below with the in stock items sorted to the top.