I did a little accuracy test with the LFCD just yesterday.
To make a long story long, I have always used the Lee Factory Crimp die when loading for semi-autos. I tested the LFCD for accuracy a long time ago, my tests showed enough improvement in both securing the bullet and in accuracy that I have blindly used it ever since. Lately I have read that many handloaders are having mixed results with the LFCD and most of it bad.
With all this negative talk about the Evils of the LFCD, I started to second guess my previous accuracy tests. Maybe I wasn't getting the improved accuracy I thought I was. So, I loaded up a few rounds with the crimp and a few without and headed off to the gravel pit.
The rifle was a Colt HBAR off the shelf AR-15 5.56.
This first target was Sierra 53gr HP Matchking with 25.5gr AA 2520. The heavy crimp was "heavy" a pulled bullet showed a deep groove in the bullet. The Med-light crimp showed a slight ring or groove, but just barely.
This next set of targets is all with 53gr Sierra HPMK and 26gr 748. I fired five at the crimp target then five at the No-crimp target, then I reversed it and fired five ant the No-crimp first and so on. My plan was to shoot 25 rounds at each target, but I got booted out of my shooting spot by some loggers hauling equipment into the pit, so I only fired 15 at each target.
Conclusion. Not enough of a sample to draw and real conclusion whether the LFCD improved accuracy or not, but enough of a sample that it sure as hell didn't hurt.