6.5 brass has gotten shorter

[45C]

[A5BLASTER]

Trim the ones that are long and leave the rest as is they will grow back out.

[45C]

[45C]

[Mad Charlie]

I would trim the 1.515's to 1.510 and run with it. Mainly for the sake of uniformity, probably not particularly necessary.

[grayfox]

From what I read on the forum Lapua has a rep of not lengthening much, but this also depends on how far back you're setting the shoulder during resize. If you bump the shoulder back 0.002-0.003 you might not see much growth beyond the 1.520, maybe after a few firings. If you're going back by 0.012 then who knows. I don't have any personally but that seems to be the case some have reported on here.

[A5BLASTER]

They’re anywhere from 1.520 to 1.507

Trim them too 1.505 for uniformity if you like or just trim the ones at 1.520 to 1.515 and let the others grow. This is what I would do.

But this ain't my stuff so only you can decide. As long as the necks don't touch the end of the lands when fired me personally I'm not real sure it matters in a ar if the necks are all the same length.

Just my thinking may or may not be correct. I'm like a broke watch I can be right twice a day lamo.

[Mad Charlie]

I could of sworn he originally said 1.515-1.507...

[SCJim]

I would trim them all to 1.510. If they get longer than 1.520 there could be pinching between the neck and the bullet causing pressure spikes

[45C]

[A5BLASTER]

That’s correct.
They all started at 1.515
Now they range from .504 to .516

Did you measure them the first time with a primer seated in the case?

[45C]

https://postimg.cc/gallery/1tjx6fti2/

[Mad Charlie]

What are the measurements of your sized and de-primed cases?

[SCJim]

Most rimless bottleneck cases are driven by the firing pin's impact hard enough against chamber shoulders to set them back .001" or more before firing. I've seen .007" with 308 Win cases. Normally the pressure from the gas will re expand the cases and some brass will flow to the neck lengthening the case somewhat but with mild or moderate loads it will not. I FL rezize and trim after every firing. Last evening I processed 50 Alpha 6mm Creedmore cases on their 4th firing. Below is a 20 shot group at 300 yards. Biggest pit fall of reloading is overthinking everything. Just make sure your brass and loads are all within spec and let the holes in the paper be the judge of how they perform.

[Jakal]

I would trim them all back to the shortest common length. They will continue to grow over multiple firings. You may need to trim again in about 6-7 reloads.

After that, they should stop lengthening.

As an example. My 6.5 Creedmoor case Max is 1.920 with a trim to of 1.910. Since my brass is unfired bulk, I'll FLS & trim down to 1.900 and let it go. Will recheck after first firing for growth and after about number 5 reloads. Re-trim if necessary but shouldn't need too. Case gauge it and verify.