Newb reloader question….

NJRaised

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Apologies in advance, I’m new to reloading and this may/may not be a dumb question.

I am trying to wrap my head around this concept….

I have once fired brass for a .223 rem. I take my headspace comparator, take the measurement, and adjust my FL sizing die to bump the shoulder back 2 thousandths from there. Now, do I need to trim my case length to 1.76” or does that change?

I understand that the neck will stretch after firing. If I’m bumping the shoulder back 2 thou, and trim the case to 1.76”, doesn’t that mean the neck gets longer and longer, eventually creating a problem?
 

NJRaised

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Yes, brass fired in my chamber. Only reloading for one rifle.

I guess to clarify my question,… I bump the shoulder back 2 thousandths. After being fire formed, the base of the case to the datum line is now 2 thousandths shorter than my chamber. How do I approach trimming the brass?
 

jakelly

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    You set bump to your chamber and set the die once. You trim to a specific length which you also set. Trim, like Dot3 said, after sizing.
     

    iceng

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    Size, then trim.

    Do not trim for 3 more reloads. Dont even measure it. It will change, juat ignore it for 3 reloads. Then look into trimming again.

    One of my cartridges i have 8 firings and not trimmed it since. Dont get hung up on it.
     

    NJRaised

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    So when I trim for 223, am I always trimming to 1.76” overall case length every time no matter what? That’s my question. It seems that by shoulder bumping I am changing the length of the head to datum line, but the neck can continue growing.

    Or am I understanding this wrong ?
     

    jakelly

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    Trim length on .223 is 1.750”. You trim to 1.750” and then forget about trimming for several firings. The brass will grow as you fire and work it. When it hits 1.760” or better, trim it again.
     
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    jakelly

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    This is probably a good time to start keeping brass in lots. Set your brass in lots of 100, 250, etc, you pick, work them as a lot; fire them by lot, size them by lot, trim them by lot, etc.
     

    Dot3

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    So when I trim for 223, am I always trimming to 1.76” overall case length every time no matter what? That’s my question. It seems that by shoulder bumping I am changing the length of the head to datum line, but the neck can continue growing.

    Or am I understanding this wrong ?
    The neck won’t begin looking like a giraffe neck unless you let it. Even then, you won’t be able to chamber a round due to the neck of the cartridge running up against the end of the chamber. And that would take several firings. If you can picture what’s happening inside the sizing die, the case is being squeezed and the brass has to go somewhere. While the body is being squeezed, and before the top of the die engages the shoulder, the overall length if the case (shoulder and all) gets longer. Then the die engages the shoulder of the brass and resizes it, pushing the neck and shoulder down, but there’s still a little spillage of brass left in the neck. Thats my working understanding of one element of growing cases anyhow. Some cartridges are more prone than others to growing.
     

    pabrousseau

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    Get yourself an inexpensive chamber length gage from sinclare and you will know when you need to trim cases and to what length. Are you shooting a bolt gun? If your once fired brass chambers without resistance you do not need to push the shoulder back. The advantage of knowing the chamber length is that many are longer what the books reference.
     

    iceng

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    The case doesnt magically grow like asparagus, it MAY need a trim to get it to spec, and thats it.

    You are over thinking and over complicating this. The primer pockets will flog out, or necks will split before you NEED to trim again. Yes you can trim as the case will grow slightly, but it will still chamber.

    If the case grows 10 thou each firing, you have SERIOUS problems.
     

    pabrousseau

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    Good advice given to you by regional rat August 2nd.if you can get a chamber length gage from sinclare you can find your chamber length and know when and what to trim to. If your once fired cases chamber without restance the shoulder does not need to be set back. Are you shooting a bolt gun?
     

    NJRaised

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    Like I said, I don’t have much experience reloading. Trying to conceptually understand things.

    Yes this is for a single, bolt rifle.

    Origin action with a proof 1:7 turned on by preece precision.

    Likely I will be shooting factory match ammo to start, and then begin reloading for it as I get comfortable.
     

    iceng

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    Screenshot_2022-09-22-21-58-46-56_e2d5b3f32b79de1d45acd1fad96fbb0f_compress59.jpg


    Screenshot_2022-09-22-21-59-19-60_e2d5b3f32b79de1d45acd1fad96fbb0f_compress12.jpg


    Official saami spec chamber drawings.

    You have room, and being an after market barrel which was smith'd on, id expect it to be real close, if not identical to these standards.
     
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    pabrousseau

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    Yes a custom chamber probably won't have the long throat that a lot of factory rifles have.
     

    Greenmoustache

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    For my .223 bolt guns I only measure/trim on once-fired brass LC range brass. Once I trim to 1.75 I call it a day as you won’t see anywhere near the growth with a bolt gun as you will in an AR.

    Virgin brass like Lapua .223 match I haven’t needed to ever trim.