Hey Mullins81,
Yes, you can seat and crimp a bullet with one cycle of the press handle. This is true whether you are using a single stage press or a progressive press, so let's go through these steps with the assumption we are using my old single stage RCBS Rockchucker press. We will also assume we are loading fifty .357 Mag cases that are now sitting in a wood block already sized, reprimed, case mouth expanded and slightly belled (remember, any time you bell the mouth of a case, it should never be belled any more than necessary to just barely allow the bullet to slip slightly into the case mouth), and all the cases have been charged.
At this point you will now seat and crimp the bullet in one operation of the press handle. The trick to doing this is to adjust the seating/crimping die properly. So, you place a charged .357 case in the shellholder, raise the ram to its top. Now screw the seating/crimping die into the press until you first feel the die touch the case mouth (if you have difficulty in getting the belled case mouth into the seating/crimping die, you have way too much bell in the mouth, and this cannot be stressed too much).
When you feel the die touch the case mouth, back the die back out a half turn and turn the locking ring down hand tight on the top of the press. Also backe the bullet seater plug back out a half dozen or so turns. Then lower the ram, place a bullet in place on the case mouth and hold it in place as you raise the ram and the bullet enters the die body. As the ram tops out, you should be able to feel if the bullet touches the seater plug. If the bullet does not touch the plug, it will not enter the case. In that event, screw the plug down until you feel the plug touch the top of the bullet (let's also assume the bullet you are using is supposed to enter the case about 1/4 inch when the cartridge is finished). Lower the ram perhaps 1/8 of an inch, screw the plug down to the top of the bullet again, and then raise the ram to its top. At this point the bullet should be inserted about halfway into the case to where the case mouth will eventually be crimped into the crimp groove.
Screw the plug down a little bit more and raise the ram again, thus seating the bullet a bit deeper. Continue adjusting the seating plug and seating the bullet deeper until the top of the case mouth is just at the bottom of the ring above the crimp groove. At this point your bullet should be seated at or very near the correct depth, but it is of course not crimped.
Now is the time to completely reset the die settings to crimp the bullet. First, back out the seating plug maybe a half dozen turns so it does not seat the bullet any further during our next steps. Raise the ram with the seated bullet to the top. Then loosen the die locking ring and screw the die down until it toouches the case mouth again. Lower the ram and screw the die down perhaps a 1/4 turn, hand tighten the locking ring again, and then raise the ram to its top. This will force the case bell out of the case mouth and start the case mouth to crimp into the crimp groove of the bullet. Lower the ram and examine the cartridge. What does the crimp look like? If it needs more crimp, repeat the previous procedure in very small increments until you get the correct crimp. How much crimp? The least that is necessary to do the required job. If you set the crimp too hard and deep, you will buckle the case.
Let's assume at this point you examine the cartridge, and it is seated to the correct depth and crimped just right. Put it back in the shellholder, loosen the locking ring, raise the die a few turns, and then raise the ram to its top (this is the most important key to seating and crimping in one operation). With the cartridge in the shellholder and the ram at its top position, you now screw the die down until the die contacts the finished cartridge on its crimped mouth. Then do a little more than finger tighten the die to insure it is firmly seated on the case mouth crimp. At this point, tighten the locking ring in place. Now you must screw the seating plug down and do a little more than finger tighten it on the top of the seated bullet. Lock the seating plug in place. Your die should now be set to properly seat and crimp the next forty-nine cases sitting in your loading block.
Simply put the next case in the shellholder, hold bullet in place as you raise the ram to its very top, and when you lower the ram, you should have a second cartridge finished just like the first one.
Be very aware that all fifty cases must be the same length and should have their case mouths chamfered. If the cases are different lengths, you cannot get them to crimp at the same spot on the bullet. Keep in mind, once you trim all the cases to the same length and you have chamfered the case mouths, you should not have to do this to these cases again.
I hope I have described how to successfully seat and crimp bullets so most folks can understand the process. If I have missed something, please ask.
So, in final answer to your question, you can seat and crimp your bullets in one operation or cycle of the handle. You do not have to lower the handle twice. You just need to spend a bit of time to properly adjust your seater/crimper die to fit your case and bullet. Once you make the adjustment properly, all the following cases (of the same length) and bullets will seat and crimp in a breeze.
Best wishes,
Dave Wile
