Originally Posted by
versifier
Welcome to the Guide.
There is no such thing as a dumb question in any endeavor when a serious mistake could be fatal, so ask away whenever. That's why we're here. There is, as you are finding out, a surprising amount of information to be digested in the learning process, and you will keep learning as long as you continue stuffing cartridge cases. You'll still have questions twenty years from now, but they will get more detailed and complicated as you gain experience.
That is not necessarily a simple question. All revolver rounds should be crimped for consistent ignition, hot or mild, and to prevent the bullets from being "pulled" during recoil and sticking out the front on the cylinder, binding the cylinder and inspiring the creation of innumerable new curse words in a variety of different languages. You have three crimp options, not two: roll, taper, and collet. Each has its upsides and downsides.
Roll crimping requires all cases to be of the same length, the one the die has been set for, for an even and consistent crimp on all the cases. Otherwise velocities will be erratic. Growing cases is not generally a problem for straightwall revolver cases like it is for bottleneck rifle cases, and neither is roll crimping once the die is set correctly. They work best when the bullet has a cannelure on it. The upsides are a very firm (if desired) crimp and the need not to buy a separated die.
Taper crimping is most commonly used on auto pistol cases that need to index on the case mouths but still must be crimped to prevent telescoping during the feeding cycle. A roll would prevent that indexing and rely on the pistol's extractor to keep the case from moving too far in and beyond the firing pin strike. They are also made for just about every cartridge, and many prefer them over the roll crimp because they are less likely to collapse a case neck and shoulder if set too deep. Like the roll, they require the cases all be the same length for the same reason. They will not deliver as firm a crimp as a roll, so of your two options, I would stick with the roll crimp.
BUT.....
Your third option appeared on the loading scene more recently than the other two. More properly called a collet crimp, but in practice usually referred to as a "Factory" crimp as that is Lee's trade name for them. (Because there are three different styles of Lee Factory Crimp dies, I prefer to describe them by how they work. I find it less confusing.) With revolver and bottleneck rifle FC dies when the case is pushed into the die, a collet closes around the neck and crimps the case radially. Case length is not as critical as long as the case mouths are within the crimping band of the collet. Collet dies do not require that the bullet have a cannelure, making them much more versatile, especially on rifle cases. Revolver FC dies also have a carbide ring at their bases that slightly resizes the case body with seated bullet to prevent bulged cases that won't load into the cylinder. The sizing ring makes them ideal for jacketed handgun loads, but they can be problematic when cast bullets of larger diameter are used. (Pistol FC dies are taper crimp dies with the carbide ring, and they also suck for the larger diameter cast bullets.) The rifle FC dies have collets but do not have the carbide ring and are just fine with cast bullets. Personally, I use them whenever I am loading jacketed pistol or revolver bullets, and on any rifle rounds requiring a crimp. I hate roll crimps with a passion and normally use them only on cast revolver rounds. I much prefer to crimp as a separate operation from bullet seating as I get better results. I would recommend you try one for all jacketed handgun rounds, and for all your rifle rounds (all cast and some jacketed, depending on type of action) that require a crimp, or that benefit accuracy-wise from being crimped. I think it is one of John Lee's two best inventions (the other is the collet neck sizer for rifle cases). I think of the years before they came out as the Dark Ages.