Ledd Slinger
Silver $$ Contributor
Thought I would share how I set up my FL sizing dies. We set up FL dies for headspacing, as we should, but it's also good to pay close attention to other measurements as well. I think it's very important that the dimensions of a fired case compared to dimensions of a FL sized case all match closely or you are under/overworking the brass. And if the dimensions are too far off, you could be hurting accuracy as well.
Below is a pic of the measurements I take on a fired case before sizing and after setting up my FL die for a new barrel. I do it off of once fired brass, but even better if you can shoot the same piece of brass 2 or 3 times before setting headspace on the die. I will check the fired case dimensions again after the 2nd and 3rd firings to make sure headspace is still correct and other dimensions are still within spec. Other than headpspace and neck diameter changes, there's not any other measurements you can change in a FL die, but they need to be checked to make sure the die is not grossly undersized and working the brass too hard, or grossly oversized and not reducing dimensions in certain areas. Of course your best chance of getting a good match to your chamber is the custom die route, but sometimes factory spec dies will match up ok. If not, then might want to get a die that matches better.
Side Note:
Never trust the sizes stamped on bushings, expander balls, or expander mandrels. Need to measure after sizing to get the actual measurment or you may not achieve the neck tension you are shooting for. I have seen bushings and expanders that were not the diameter stated, also seen bushings and expanders with .002" difference stamped on them, but they both sized necks to the same exact diameter. Machining doesn't always come out perfect so thats gonna happen due to human/machine/tooling errors. Just make sure you know what the actual measurements are on the case. For example, if you are using a certain bushing or expander and accuracy is great, then one day you use a different bushing or expander of the same stated size, whether the same manufacturer or not, and you don't re-measure the sized cases to check that everything is the same, you might be changing characteristics of your load without immediately knowing why that happened.
Below is a pic of the measurements I take on a fired case before sizing and after setting up my FL die for a new barrel. I do it off of once fired brass, but even better if you can shoot the same piece of brass 2 or 3 times before setting headspace on the die. I will check the fired case dimensions again after the 2nd and 3rd firings to make sure headspace is still correct and other dimensions are still within spec. Other than headpspace and neck diameter changes, there's not any other measurements you can change in a FL die, but they need to be checked to make sure the die is not grossly undersized and working the brass too hard, or grossly oversized and not reducing dimensions in certain areas. Of course your best chance of getting a good match to your chamber is the custom die route, but sometimes factory spec dies will match up ok. If not, then might want to get a die that matches better.
Side Note:
Never trust the sizes stamped on bushings, expander balls, or expander mandrels. Need to measure after sizing to get the actual measurment or you may not achieve the neck tension you are shooting for. I have seen bushings and expanders that were not the diameter stated, also seen bushings and expanders with .002" difference stamped on them, but they both sized necks to the same exact diameter. Machining doesn't always come out perfect so thats gonna happen due to human/machine/tooling errors. Just make sure you know what the actual measurements are on the case. For example, if you are using a certain bushing or expander and accuracy is great, then one day you use a different bushing or expander of the same stated size, whether the same manufacturer or not, and you don't re-measure the sized cases to check that everything is the same, you might be changing characteristics of your load without immediately knowing why that happened.
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