New vs once fired

[SneakyThunderCat]

So I got 100 rounds of new brass last year for the hunting rig. I ran them through my FL die, trimmed the cases to spec and loaded them up and found a good load that shoots well out of my gun. I'm about through the new brass and will load up my first batch of "once fired" brass soon. They will be ran though the FL die again and loaded up with the same load I have found to work the best in my gun. To you guys that have done this before, have you seen much fluctuation in fps? Considering I ran the new brass through the FL die before loading, I would think it should be pretty close with the new brass fps vs once fired fps.

Also, is case trimming again after running the brass through the FL die necessary the second time around? I plan on doing everything exactly the same as the first load process, but not sure if it's necessary. This is a hunting rifle so these next 100 rounds will last me quite a while, so I'm not concerned whether or not I get 10-15 reloads out of the brass. Just looking for opinions from more experienced reloaders.

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[Lawnboi]

Measuring will answer all your questions. You need to measure your headspace with a comparator. Determine how much your brass grew, and what it was at prior to firing. FL size minimally, trim if needed, measure after sizing.

FL sizing without measuring is what will leave you with possible problems down the road.

 

[EdP]

You really don't know what your original sizing did because you don't know what size the brass was. Now you know that your brass is essentially chamber dimension for that specific rifle. That's a good starting point to work from. Deprime a case w/o resizing, measure using a headspace gauge and set up your resizing die to set the shoulder back .002". (NOTE: If you have not done this before there is plenty of "how to" info on the web on how to set up your die.) Resize your cases, measure to determine if a trim is needed. Make sure the case will chamber easily as a check on your work. Load some up and go shoot. I would not expect much difference in velocity if any at all, but accuracy might be a bit better.

Personally I would not load all 100 cases but probably just 20 or maybe 40. At some point you may want to do more load development for accuracy or a different bullet for different game or for a different rifle of the same caliber.

 

[Harvey_NW]

Typically after brass is fired and properly sized for your chamber your velocity will get more consistent. If you're loading near pressure you may see indications on the second firing and have to back your charge down a bit, as there is less overall space in the chamber.

As far as trimming, you can either go by the book trim specs, or measure and see the maximum length your chamber will allow. I used to trim every cycle to keep everything consistent but I quickly found out it's a waste of time, and now only trim when needed.

 

[wind gypsy]

If you minimally size the case only enough to ensure reliable function, i would assume velocity will increase a little bit.

Only trim if sized brass is long enough to justify it.

If you bottom the die out and work the shit out of the brass, you are less likely to have a velocity increase, more likely to need to trim the brass, and will likely have shorter brass life.