Originally Posted by
DougGuy
The bigger you go with the boolit, the more case neck tension you will get. However this comes with a price. First they may not plunk and twist in your barrel with the throat as is from the factory, so you seat deeper as a workaround, you MUST compensate the load data to allow for lesser case volume under the seated boolit or risk an over pressure event.
The other thing, if you use the FCD with the carbide ring in the bottom, it may size your boolits down in the case it they are of sufficient diameter to seal in the bore so you load a .358" and run it through the FCD, now pull the boolit with a kinetic puller and mic the boolit see if it is swaged down in size. The secondary effect of the FCD is that it squeezes the brass AND the boolit down as it passes, and when it comes back up off the boolit, the brass case springs back and you lose a LOT of that all important case tension you had before using the FCD.
Smaller diameter boolits usually can go through the FCD and not be resized. The FCD will definitely swage down .358" unless you got an exception to the rule FCD, they are not all the same. Seems to be the luck of the draw on what the FCD actually sizes a loaded round to.
And, the hardness of the boolit has a LOT to do with the finished size after using the FCD. Softer boolits will come through the same die a different OD on the case than a harder alloy boolit and the resulting case tension will be widely varied depending on alloy used.
The most dangerous thing you want to make sure to avoid, is setback. Those boolits at the bottom of the stack that moved forward in the case, not enough tension to hold them, as you feed a round from the magazine that doesn't pass the "push test" and it gets pushed back into the case when it hits the feed ramp, now you got a shorter COA, but with the same powder charge you intended to use for the longer COA, and if your loads are anywhere near the upper end of the allowed pressure, setback of even .010" can send pressures skyrocketing.
If it gets set back far enough, there is the very real possibility that you can KB the gun in your hands, detonating most of the rounds in the magazine, sending shards of brass, lead, powder granules, broken plastic or wooden grip panels into your hands, face, and any bystanders in close proximity. Ask me how I KNOW about this one!