Question about trimming

P

Paulyester

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Jul 15, 2025

#1

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• #1

I’m loading some 6 Dasher, 3rd reloads, Alpha brass. My question, and this goes for every round really, but should you trim. My brass is well within spec, however they vary individually by 20-30 thousandths in length. Is it worth trimming? Same general question for 6.5 Creedmoor. I’ll have cases ranging between 1.910 and 1.920, usually around 1.915-1.917, is it worth trimming them or only if they are out of spec.

This is for long range PRS and NRL shooting.

 

straightshooter1

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#2

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• #2

It's good to have uniform case lengths.

It has to do with getting uniform blowby during ignition as the trailing part of the bearing surface clears the case mouth.

Longer necks are helpful when seating bullets long so that the bullet maintains its runout in chambering the round.

 

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R_A_W

Miderator

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#3

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Case length variance impacts precision most significantly in the presence of a bad carbon ring, although that’s really a cleaning issue.

I pretty much don’t trim, unless absolutely necessary & I don’t want to buy more brass. Not the best practice, but not something I am willing to put much time into. I haven’t ever seen 20-30k length variance though.

 

ShtrRdy

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#4

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If you trimmed to 1.915" would that get most of them?

 

sinister

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Precision is about consistency.

If you don't care about group size keep carrying on mass-producing whatever comes out of the end of your handloading process.

 

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Maurygold

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#6

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You need to trim every time for consistent brass. I usually measure 10 then set my trimmer to the shortest and it stays there.

 

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Cynical

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#7

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Paulyester said:

I’m loading some 6 Dasher, 3rd reloads, Alpha brass. My question, and this goes for every round really, but should you trim. My brass is well within spec, however they vary individually by 20-30 thousandths in length. Is it worth trimming? Same general question for 6.5 Creedmoor. I’ll have cases ranging between 1.910 and 1.920, usually around 1.915-1.917, is it worth trimming them or only if they are out of spec.

This is for long range PRS and NRL shooting.

Click to expand...

Is there a typo in your post? Between 1.910 and 1.920 is ten thousandths. And if the bulk are 1.915-1.917, that’s pretty solid.

SAAMI spec case length for 6.5cm is 1.920 - (minus) .020. So anything between 1.900 and 1.920 is “in spec.” Most of the time people trim brass when it reaches max length or more (1.920+) and set the trimmer to between 1.910 and 1.915.

 

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Kaldor

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Sunday at 12:48 AM

#8

• Sunday at 12:48 AM

• #8

You will always have some wierd outliers that seem to come up short. In your case, Id set the trimmer to 1.915 and trim them all every firing. Its faster to trim than it is to measure in 95% of cases. Take the short ones that dont trim anything, and set them aside for foulers if you want, but honestly 5 thou shorter at 1.910? Your rifle probably will not be able to tell the difference.

 

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