Do you have to size before trimming?

PanhandleGlocker

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Sorry if it’s been asked before but do you have to size your rifle brass before trimming to your desired length? Was just wondering because I have the Frankford Arsenal Case Prep Center with the case trimmer built in and it’s difficult to hang onto the case with my thumb and index finger after the cases have been lubed and sized. Probably a silly question but I figured y’all would know the answer. Thanks guys.

After writing this I guess it wouldn’t matter if you can trim before because I’d still be stuck holding onto a lubed case trying to prep the neck and primer pockets at the prep center….
 

Rez Exelon

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My process for what it's worth.

1. Decap --- universal Lee decapper
2. Tumble clean.
3. Dump in pan, spritz with mix of lanolin+995IPA and hand mix
4. Size
5. Check if trimming is needed, trim if needed.
6 Clean Primer Pocket/Chamfer/Deburr
7. Uniform flash hole (if new brass)
8. Prime
9. Load or store.

I do steps 5-7 on a bench lathe which goes really quick with my setup. I like the lanolin/IPA mix because it seems to prevent sticking but is "lighter" than some other types of lube I've used. I don't really have any holding on issues. Not sure how the lathe method would compare to the case prep center method in that regard though.
 

dennishoddy

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Usually that's best to trim after sizing due to the expander plug pulling on the shoulders of the case slightly on withdrawal. If you're neck sizing only then I don't think it would matter either way, but more experienced loaders might have more details.f
This ^^^^^^trim after sizing then deburr and load.
 

ForsakenConservative

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Each time a cartridge is fired, the hot brass flows forward and outward, requiring the cold-form sizing. The brass is now a bit “thinner”, and has to be squeezed back to dimension. The result is a long case that must be trimmed after sizing because sizing will change the length-how much? Always different. Cartridge type/size, pressure and actual chamber dimension are some things that will influence brass flow. My pistol cases? Never have to. My 338 Win Mag? Rarely. My 25-06? Nearly every time.
Short answer, trim and chamfer after sizing.
Anyhow, that’s my little mechanic’s brain understanding…..
 

swampratt

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I clean off the lube after sizing then trim.
One note though is that trimming a case is the least important thing for me unless I am shooting past 1000 yards.
Read this brass fail test and look at the group sizes and NO trimming and mixed head stamps.
Well I did trim once the case gets so long and into the rifling.
 

Moparman485

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Short answer, yes, as it is when you are resizing, or “squishing” the brass back into spec when the “stretched” brass can be most noticed, for lack of a better way to explain it. That and the process of sizing the neck can also draw the neck out as well. I generally follow the process of:

1) gather spent brass by caliber
2) wet tumble the brass to knock off range gunk to keep dies clean and make spotting damaged cases easier
3) lube cases (if a caliber requiring lubing)
4) resize/deprime
5) wet tumble to remove lube and clean primer pockets
6) measure brass and sort by what needs trimmed, what needs primer pocket crimps removed, and what is ready to load
7) trim/deburr as necessary
8) sort by headstamp
9) prime case
10) powder charge case
11) press Projos
12) bag and label
13) load and launch
14) repeat
 

delta6

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For my .223, .308, etc, range ammo:
1. Tumble to clean
2. Lube
3. Size-Dillon
4. Trim-Dillon
5. Debur mouth and primer pockets if necessary
6. Short tumble with corn cob-mineral spirits to remove lube
7. Prime/load and store/shoot

I load most of this ammunition on a Dillon. Since the brass is all prepped, I use a universal decapping die in the first position (sizing) and that insures if there is a piece of debris in the flash hole, this die removes it.
 

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