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Thread: Brass length - trimming?

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    Member 2dawgs's Avatar
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    Default Brass length - trimming?

    I'm just starting out reloading and am processing my first batch of once fired brass.
    .300 WinMag
    Brass is Remington and Federal (both high nickel/chrome looking?)
    My question, my once fired brass measures between 2.573 and 2.595. The Speer book says trim length to 2.620, and Barnes book says trim length to 2.620 max, 2.610 min. If this is the case, why is my brass so short from the getgo. I assume it will grow over time and shooting...but that much? Am I missing something here? Any insight and advise is appreciated.
    Last edited by 2dawgs; 02-02-2016 at 19:26. Reason: Spelling

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    Member Akheloce's Avatar
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    Default Brass length - trimming?

    Yes, it will grow. You don't want it to, but it will. Particularly with a belted mag, it will get thin just above the belt as it flows to the neck. This will eventually cause it to get so thin, that the case head could separate just above the belt. Use a pick (using the point) to feel along the inside of the brass for a lip above the belt (inside the case). When you can feel it, the case is done.

    Don't stress the trim to length right now. As long as you make an even perfectly flat trim (90 degrees to the case axis), you're good imo. In other words, trim it until you get fresh brass on the full diameter of the mouth, then stop.

    For hunting accuracy, that'll work. For competition, you're in for a lot more work, and you'll figure it out with experience.

    Edited to add:

    One cause of premature brass failure is oversizing cases, when you size them per most instructions, you're making the brass so short, that a gap is formed between the shoulder of the chamber, and the shoulder of the brass. This allows the brass to expand to fill the void, while the head is held by the extractor. This is the reason brass gets thin down by the belt.

    Adjust your dies so that when sizing, you bump the shoulder .001" to .002" from the original fired size.
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    Quote Originally Posted by 2dawgs View Post
    I'm just starting out reloading and am processing my first batch of once fired brass.
    .300 WinMag
    Brass is Remington and Federal (both high nickel/chrome looking?)
    My question, my once fired brass measures between 2.573 and 2.595. The Speer book says trim length to 2.620, and Barnes book says trim length to 2.620 max, 2.610 min. If this is the case, why is my brass so short from the getgo. I assume it will grow over time and shooting...but that much? Am I missing something here? Any insight and advise is appreciated.
    Trim length is usually about .010 less than the case length spec.

    No doubt the case length will grow, with full power loads, in which case, trim it back. It needs to be LESS or same as the case length spec.

    If you want to avoid the thinning that Akheloce, mentioned, don't set the shoulder back too far in sizing.

    The 300 WM is similar to 7mm Rem. Mag. I suggest using a Neck Only sizing die. The neck is so short that you won't even hafta lube the case. But do brush out the inside of the Neck.

    That's what I do with my 7mm Rem, and my 7mm Weatherby, and it works great. Full length sizing either of them is a PITA.

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    Supporting Member iofthetaiga's Avatar
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    Quote Originally Posted by Smitty of the North View Post
    If you want to avoid the thinning that Akheloce, mentioned, don't set the shoulder back too far in sizing.
    ...Or at all.

    IMHO:

    • So long as your brass chambers, and bolt closes without significant resistance, there is no cause to do anything but neck size only, ever.
    • So long as your case mouths are reasonably square, and case length below max spec. length, there is no cause to trim.


    Make sure to use a little lube on your case necks when you size them; avoid excessive friction between brass and tooling. The object is to size the neck diameter only. You don't want to shove the neck and shoulder down, and then pull it back up during sizing, not even .001. That serves no purpose but to unnecessarily work your brass...to it's detriment.


    Quote Originally Posted by 2dawgs View Post
    If this is the case, why is my brass so short from the getgo. ....Am I missing something here?
    You're not missing anything. Brass is often well below max spec. length. I have lots of brass that has never been trimmed and likely never will need to be.
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    Member 2dawgs's Avatar
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    Ok, thanks guys. All of this brass has been run through my .300. So it should be fire formed to my chamber and (should) not need FL sizing, am I reading this correct. The next question is, is there a way to use my FL die to just do the neck or just get a neck size only die?
    Thank you all for the help.

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    Supporting Member iofthetaiga's Avatar
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    Quote Originally Posted by 2dawgs View Post
    Ok, thanks guys. All of this brass has been run through my .300. So it should be fire formed to my chamber and (should) not need FL sizing, am I reading this correct.
    Yeah, and here's the test to prove to yourself whether they're ok, or not: Take a piece of the fired, unsized brass in question, gently chamber it and close the bolt. Does it fit? It should because it just came out of that same chamber, so logic dictates it should go right back in, yes? Now, neck size it and repeat the same test. Does it still fit? If not, it can only be because you pulled the shoulder forward when you pulled the sizing button out through the neck during sizing, right? I submit it's better to learn how not to do that, rather than to set the shoulder back every time just so you have room to turn around and pull it forward again on the way out... (Things that reduce coefficient of friction (tapered buttons, carbide/nitride metals, sizing lube, and a smooth gentle cycling of the press, all help reduce push/pull on the case during sizing).
    The next question is, is there a way to use my FL die to just do the neck or just get a neck size only die?
    You can do a pseudo neck size with a FL die by only going as far down as necessary to size the neck without setting the shoulder back, but you'll still get body engagement/sizing. There's no way around that. A neck only die is the better tool for the job.
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    It is very important that you lube the inside of the case neck. I highly recommend a lube that will not prevent the powder from going bang. Such as Hornady One Shot. When I first started reloading I lubed the inside of the neck with RCBS lube. I never wiped any lube out of the case after resizing and assumed that crimping the bullet was a good thing to do. Well the lube in the case prevented about half of the rounds from going off. The crimp made pulling the bullets with a kinetic puller almost impossible. I ended up pulling them by running the bullet up through the threaded die hole in the press and latched onto the bullet with side cutters top side of the hole then ran the ram back down and when the side cutters holding the bullet got to the threaded hole in the press they stopped while laying flat across the top of the press and the shell holder pulled the case down separating the bullet from the šase. I dumped the inhert powder but save the bullets inspite of them having little dings where they were gripped by the side cutters.

    I cleaned all 500 cases and started over. That really had me wondering if reloading was worth it. I have a tendency for learning the hard way and a 500 round boo boo is really emphasizing that.😉

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    How accurate do you want the rounds to be? If you are looking for pin holes at 200 yards, then the trim to length thing makes a bigger difference. If you are OK with 1 1/2 moa at 100 yards, then exact trimming is really not that big of a deal. If you trim, there will be burr and you need chamfer and deburr the mouth.

    Neck sizing greatly reduces the need to trim and should make your loads a little more accurate. You need to make sure the rounds cycle good before hunting. You should do that regardless of full length or neck sizing. Some schools of thought want the round to be a little loose when it enters the chamber to ensure proper feeding, hence the full length sizing. I full length size my 375 Ruger and 35 whelen rounds to make sure they chamber in a dangerous game situation. My 30-06 is an autoloader and it needs a bit of room to chamber correctly so it is FL sized. My accurate long range stuff I try to neck size.

    Also, the Lee factory crimp die instruction sheet tout that one of the benefits is that "case neck size is not critical" when crimping. Meaning the starting pressure at the case mouth is affected more by the crimp than the neck tension of slightly different lengths. Believe it or not, just another way to look at the issue.

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    What iofthetaiga said is right on. One little added detail. If you resize the body at all, squeezing in the sides of the case makes the brass longer as there is only one direction the brass can move and that is forward. Once you have fire formed your brass, you don't want to mess with it any more than you have to. Squeezing down the neck just enough to get good neck tension is all you want. Most brass comes from the factory too short as it is safe that way and it will grow. Too long is dangerous as it can cause the end of the neck to be crimped very tightly on the bullet if it runs into the end of the chamber causing very high pressures. Short is ok, too long is very bad.

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    Quote Originally Posted by elmerkeithclone View Post
    It is very important that you lube the inside of the case neck. I highly recommend a lube that will not prevent the powder from going bang. Such as Hornady One Shot. When I first started reloading I lubed the inside of the neck with RCBS lube. I never wiped any lube out of the case after resizing and assumed that crimping the bullet was a good thing to do. Well the lube in the case prevented about half of the rounds from going off. The crimp made pulling the bullets with a kinetic puller almost impossible. I ended up pulling them by running the bullet up through the threaded die hole in the press and latched onto the bullet with side cutters top side of the hole then ran the ram back down and when the side cutters holding the bullet got to the threaded hole in the press they stopped while laying flat across the top of the press and the shell holder pulled the case down separating the bullet from the šase. I dumped the inhert powder but save the bullets inspite of them having little dings where they were gripped by the side cutters.

    I cleaned all 500 cases and started over. That really had me wondering if reloading was worth it. I have a tendency for learning the hard way and a 500 round boo boo is really emphasizing that.
    haha, that sucks. Seems I always try the easy way which usually turns into the hard way, if it weren't for bad luck I wouldn't have any luck at all hahaha.

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    Another bo bo that cost me a gun. My old reloading manual said 45.9 grains was max load for a 270 with 130 grainers. I had a 270 and zactly 20 rounds of brass. I was still in my first week of reloading and I think i was loading those same 20 brass for about the 5th time that week. After 5 times in a week a fella should remember his charge of powder right? Well in my head that 45.9 grains became 49.5 and I loaded them that way. The very first one that I fired sent crap back through the bolt and a itty bitty hunk of something cause my cheek to bleed just below my shooting eye. The bolt was stuck shut and I had nothing with me to open it and really didn't have the desire to open it. When I got home I got a short 2x4 and showed it some love until it opened. The primer was gone and the primer pocket was enlarged and ya couldn't read any of the writing on the case. I took the gun to Keith Rose at Roses gun shop. It was toast. I was milking cows for three dollars an hour back then so buying a rifle was a big deal. It was six months before I got my second rifle. Ya might say that lesson stuck with me. I've never taken anything for granted since when it comes to reloading. I have also decided that I don't need to wring the most velocity out of my rounds. I stay near the top but have usually found that the accuracy load is somewhere just below max for a given powder.

    I have worn out enough 243 barrels to know that a 70 grain bullet running 3600 fps will give you about half the case life and barrel life of the same bullet running 200 fps slower. The good news is that the coyotes don't know the difference. Just food for thought.

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