Achieving ideal case length with fired brass

OP
jjohnsonElknewbie
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The first step is figuring out an accurate measurement of what your particular chamber measures from base to the shoulder datum. If it’s already been fired once in that particular chamber then pick a short piece that’s under trim max, measure to the shoulder datum and write that number down, neck size it (or use your FL die and don’t touch the shoulder) and fire it again. If it doesn’t grow or only grows by 1-2 thou then your probably there as far as the brass completely expanding to that particular chamber.

It’s really important to have accurate number for shoulder bump and not over size your brass, I have seen case head separations in as little as 3 firings from guys camming over a FL die on a standard shell holder and pushing shoulders back 10-12 thou every time they sized.

lots of different thoughts on trimming, IMO it’s good to know your actual trim length in your chamber so your not trimming to short but you can also pick a middle of the road number between min and max and trim to that, or find your shortest piece of brass and trim everything else to match.

It depends on what type of trimmer you’re using, some base off the shoulder so you need either fired cases that are completely formed or good consistent shoulder bump to end up with consistent trim length. Others base off the case overall length so they are cutting pretty much the same no matter where the shoulder is at when they are trimmed.

Your plan sounds pretty good, you just need some hard numbers on your chamber before going to crazy.
Thank you for the comments, much appreciated. Is it safe to say that a case gage and comparator give you the same information, except the comparator gives you an actual measurement of headspace vs. a simple inside or outside specification reading? If so, it may make the most sense and increse consistency to get the comparator vs. the gage.

Thoughts?
 

wind gypsy

"DADDY"
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I'm not sure what you mean by case gauge but get a comparator. Its useful for all cartridges and different chambers of the same cartridge to know how much your brass is growing or being sized.

FL sizing brass squeezes it and typically makes it longer rather than shorter.

I didn't see it mentioned but the other thing you need to consider is neck thickness of your necked down 30-06 brass. When you decrease the diameter of the neck you're squeezing that same amount of brass into a smaller circle and thus making it thicker. If the chamber is on the tighter size you might run into neck clearance issues. Measure neck diameter of loaded brass compared to fired and unsized brass for comparison.
 

ckleeves

WKR
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Yes, you just need a comparator. Which is exactly like it sounds, it compares your fired brass (that’s sized to your chamber from firing) to your brass after sizing. Simple explanation-Your not measuring to any number in a loading manual or anything like that, simply comparing fire formed to full length sized.

Lots of vids on YouTube, there are multiple ways to skin this cat but being able to measure and understand what your die is doing to your brass is important.

I think you can get a Hornady set that includes both bullet ogive comparators and shoulder comparators for pretty cheap and they work fine.
 
OP
jjohnsonElknewbie
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Sounds good and since I will be reloading for .35 Whelen and .308 in the future, a comparator set is probably the best value.

The case gages I've been referring to are below. The Wilson doesn't provide more than an in spec. or out of spec. measurement. However, the Whidden model has hashes in the thousandths and clearly notated go and no go for a particular cartridge based on SAAMI spec.

https://lewilson.com/case-gage

https://www.whiddengunworks.com/product/case-gauge-3/
 
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