Do I need to Trim all brass to 2.000" so all are the same length?

little_scrapper

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I have prepped about 60 pieces of M118LR brass for a ladder. About 40 pieces of once fired and 20 pieces of twice fired. The long ones I attempted to trim to 2.005". Some came out a thou or two short and some were already as low as 2.000" or 2.001" so no trim obviously.

Therefore, I have a batch of brass that is all FL resized, shoulder bumped to 1.622" - 1.623". However my overall length runs from 2.000" to 2.005".

Do I need to trim the longer ones back to match? If so, to …. what? Or just wait for the short ones to catch up to the longer ones?
 

K31Scout

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If you crimp it with a seating die then I believe my die instructions say they need to all be the same length. I dont use that feature so I cant be 100% positive.
 

bluegrasspicker

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In load development I try to eliminate as many unknowns as I possibly can. That way I'm as confident in the results as I possibly can be.

If I were in your shoes I'd try to just use the 40 once-fired brass that's closer to the same length for the ladder test. Then they'll be 2* fired and you can mix them in with the rest of your brass.

With that said, I've never checked to see what difference 1* vs 2* firing makes or what a ~.005" variation in brass makes. I just follow the simple principle of minimizing unknowns.
 

RegionRat

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Aug 10, 2019
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Depending on the crimp or no crimp like K31Scout said, I wouldn’t worry too much.

If you are very picky, you can bring the whole batch to the same length, but to be honest the concept that you are willing to mix 1X with 2X is the same as if these are sensitive to within 5 mils. The difference in 1X versus 2X may or may not make a difference and only a test with your situation can answer that question. I doubt the difference in trim length will be seen but I wouldn’t go as far as 10 mils for example. That is just instinct and not measured. Neck tension is complicated and I don’t see 5 mils making a significant change in the hoop strength of the neck to be concerned. Just make sure you are not crimping.

Depending on you chamber and reloading process, the effect of cycles may or may not be an issue between adjacent batches. So for example, some day you may want to intentionally test the difference between 1X and 4X to see if they group together or require different dope. Cleaning methods and annealing can have huge effects, but that is another thread...

ETA: with machines that indicate off the shoulder, a 2 mil spread isn’t unusual. So you 5 mil spread is just breaking out into being noticeable. I know guys who allow 10 mils in a batch and don’t blink.
 

little_scrapper

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I am not crimping any rounds. The 1F & 2F brass are not mixed per se. My first 8x charge levels are all 1F brass. This load range covers the area I am most interesting in based on my very coarse ladder last weekend. The 2F brass are the last 4x sets of charge weights.

I really need to get a chrono. Soon as I recoup from buying all the loading equip I will have one.
 

powerspc

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In load development I try to eliminate as many unknowns as I possibly can. That way I'm as confident in the results as I possibly can be.

If I were in your shoes I'd try to just use the 40 once-fired brass that's closer to the same length for the ladder test. Then they'll be 2* fired and you can mix them in with the rest of your brass.

With that said, I've never checked to see what difference 1* vs 2* firing makes or what a ~.005" variation in brass makes. I just follow the simple principle of minimizing unknowns.
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What this guy says. Does it matter? The fact that no one will "know" for certain is enough to eliminate it from possibility. Use the 40 1x brass that is the same (nearly) length. That way it doesn't matter whether it matters or not.
 

LG65CM

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I load 6.5CM. Case length is 1.920 and 'trim to' is 1.910. For load development I use 1XF brass and trimmed to the same length, 1.918. After that, I segregate my brass in times fired. Their trim length is 1.918" or shorter. The shortest piece I've measured was 1.914".

Which I don't worry about. I got the load developed and the .000 to.004s" difference in brass length will get lost in the noise. I don't like to trim my brass any more than I have to or any shorter than necessary. That trimmed brass has to come from somewhere (the case) and believe trimming to much shortens case life.

So, to OP, my suggestion is, use same numbered fired cases and brass trimmed to same length for your load development. From there on keep your brass within spec for length and load and shoot it. I am not a world class marksman so I can't tell whether its case length or noise, like my shooting, that makes a diff in my groups. 2centsworth, lg
 

Outcome

Monica
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Feb 22, 2017
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I trim my brass in batches. Once say 30% need to be trimmed, I'll just trim them all. I dont constantly check and keep my brass at the min length.