Ala Dan, I'm glad you were able to gain something from my post.
My comments apply to handgun rounds only. I have tested the FCD so far in 9mm, 38/357, 40, 45 ACP and 45 Colt. I have sold ALL of them, but in the interest of testing and such I have another FCD on the way to me as we speak. The price was good and I thought of something I didn't try last time, my own curiosity more than anything else.
The problem I have seen with the FCD is two sided. The first and far more regular problem I see is greenhorn or ill-advised reloaders promoting them as the end-all cure-all for problems in the relaoding process. For example, a new reloader is having problems with some rounds failing to chamber and is advised to get the FCD, it will size out and smooth out the problems and feeding will then be 100%. Well DUH!!!!!! Of course it will, but anyone that takes that approach is an IDIOT!!!! There is a reason for the problem and ignoring it will eventually get you a blown up gun! Hopefully that guy won't get hurt beyond his pride. A thinking man is going to figure out what the problem is, and correct it rather than bandaid over it and hope. The FCD is a rather recent innovation, makes me wonder how all those untold hundreds of millions of handloads made it through guns much below the equal of what we have today.....
The second side I see to the FCD that is a potential problem is brass inconsistencies. Most all of us reload mixed brass, and in as large of quantities as we can afford. Sorting brass is a PITA, and frankly it is not going to happen for me. I shoot several thousand rounds per month, and keep several thousand more rounds loaded. 10K rounds on hand at any given time is normal for me, the scale is far too large to have to worry about headstamps. The sizer ring is carbide and fixed in size, but the crimp is adjustable, so far so good. The rub comes in with thick-ish brass, you can't adjust it down far enough to crimp well and not have it pass fully over the bullet length. So when you get the adequate crimp it has just swaged the bullet down a half thou to a full 2 thousandths in some brass!!!! It does not allow for me to load .358" bullets in my 38 and 357" in my 357, one size is all you are going to get but that is only the beginning. Some of the brass out there has thin walls and works OK, like Remington and Federal. Now we get to the scary part. You are loading up some 40's or 45's, using your FCD becuase it is the end-all (stay with me here) and you will have NO problems. You are using mixed brass, and for the sake of ease we will say that F brand has .009" walls and brand SB has .011" walls and that this just happens to be 40 S&W we are working with. The brand F brass is sized down to .399" ID and everything is good though a little more case tension would not hurt, a bullet is seated and the FCD sizer ring just barely touches the case, doing nothing but crimping the bullet. The brand SB comes along and is sized down to .3975" ID, we have a perfect size for a .400" bullet and we seat it. The brass is now .002" larger OD than the brand F, so the FCD sizes the round down .002" just like it was designed to do, and make everything nice right? Nope, now we have a bullet that is .398" in diameter if we pull it from the case, and the REALLY scary part is the bullet is only being held by the taper crimp and .0005" of case tension!!!!!! It is loaded into the magazine and the slide picks it up, the bullet nose hits the feed ramp, the bullet has little tension on it and crimp does squat to prevent setback (we all know that right?) so the bullet is set back into the case by .050" and BOOM!!!!!!!!!!!!!!!!! We just blew up a perfectly good pistol, and probably blame it on a lack of case support since we used a 40 in this instance.
There is no free lunch. There is no cure-all to the reloading process. If there is a problem it MUST be addressed and not simply covered up.
For the astute loader with enough experience to know what is happening and what the consequences are the FCD is a GREAT idea, and it works famously. For the tyro or the less than attentive it spells disaster.
Over the last couple years and a half dozen or more forums I have been beat up on this very subject, only to have the detractors disappear when asked to explain how the above is not going to happen. The Lee FCD IS a good tool, but it must be used correctly or there will be penalties. I just don't want to see someone take advise in good faith without all the information and end up paying DEARLY for it. Too few people understand exactly what they are undertaking when reloading, and yet they are the first to advise that all the problems went away when they bought an FCD. I think we hear of VERY few of the total count of reloading accidents. Guys like Mike Irwin that are big enough men to stand up and say they screwed up are few and far between these days.
I have blabbed long enough. FWIW, that is my take on the situation. Use it or leave it.