Saami minimum case length for 6.5 Creedmoor

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kilotanker22

New member
So I goofed up and trimmed a few cases to 1.890" for my creedmoor. I have been unable to find the Saami minimum case length for this cartridge.

Any help would be appreciated.
 
Why would it matter?

1.890" is 0.03" below the listed (max) length, 1.920". Its not even the 0.1" usually used as "trim to length". I wouldn't worry about it.
 
SAAMI case length is 1.920 -.020. That means 1.920" minus 20 thou. The 20 thou being the tolerance and minimum case length.
However, 10 thou below minimum really isn't going to cause you any grief. You might have to adjust your seating die a tick but doing that by just 10 thou isn't easy.
Anyway, go here, then click on 'Technical Information' then scroll down and click on 'Rifle' then wait for the .pdf to download and scroll down to Page 39 for their 6.5 Creed drawing.
https://saami.org/technical-information/cartridge-chamber-drawings/
 
I've shot some 6.5 CMs at 1.896 trim length with no problems.
In fact, the group size average was just about right on my long term average.

Trimming the brass down by 0.020 will increase velocity by about 10 fps.
You can balance that out by seating the bullets out of the neck by an additional 0.020, if you have the space in the chamber.
If not, just let the velocity increase.

If you neck size, you'll may see the neck stretch a bit on most of the brass every time you resize so your error will gradually become less of an issue.
 
Trim length

When I first got into loading rifle 35+ years ago I asked about trim length. A very experienced benchrest shooter told me that what you trim to is not vital, you can go as much as -.030, but it is critical they be EXACTLY the same.
 
When the M14 variants were still kings of the competition, competitors would figure that when fully resizing military brass it could be reloaded four times before head separations started. So they would toss that brass after the fourth reload. Knowing they were going to scrap it at that point anyway, many just figured it would grow about 0.01" per load cycle and went ahead and trimmed -0.040" off after the first resizing so they wouldn't have to trim it again before it was scrap. It made no difference they could see in that discipline.
 
Trim to length is listed as 1.910 on every manual I have.
Click to expand...

My bad, sorry, my mind was misplacing the decimal.

Still, as usable cases they shouldn't be too short. For uniformity no, but they will work fine as long as there is enough neck to properly hold the bullet.
 
Unclenick said:
When the M14 variants were still kings of the competition, competitors would figure that when fully resizing military brass it could be reloaded four times before head separations started. So they would toss that brass after the fourth reload. Knowing they were going to scrap it at that point anyway, many just figured it would grow about 0.01" per load cycle and went ahead and trimmed -0.040" off after the first resizing so they wouldn't have to trim it again before it was scrap. It made no difference they could see in that discipline.
Click to expand...
Same thing with Garands in 30-06 and 7.62 versions.

Best accuracy in these service rifles was with new cases. Their bolt faces weren't squared up like bolt action match rifles. Extensive tests proved resizing fired cases from them didn't square up the case heads. Such cases shot test groups near twice the size as new cases produced.
 
That is no surprise with an off-axis case head. It will introduce an additional recoil moment when the short side slams into the bolt face.

I lucked out with my M1A. It kicks out square case heads. The way I confirmed that was by using the Wilson fired case holder and setting them backward in the Wilson trimmer and running the trimming cutter in just far enough to begin marking the head face. It does that evenly all around if I didn't load the round so warm that the extractor started to bend the rim.
 
I went ahead and trimmed 100 cases to this same length. With the same load of Reloader 16 vs the cases that are trimmed to the normal length I increased velocity by 21 fps average velocity. That is with the bullet seated the same distance from the lands.

Group size with these shorter cases went from about .5 MOA to .9-1 MOA. Not enough of a difference to make me really miss targets. I was picking off rocks at 300 yards today that are less than 1 MOA diameter.

I also noticed an increase in SD of about 4 fps with the shorter cases as opposed to the longer cases
 
15 round group fired in quick succession measured a hair under 1.5 MOA. If I take my time and keep the barrel cool I stay around .9 MOA
 
I would expect a shorter case to reduce velocity due to having less grip on the bullet. Were ambient temperatures the same? Were you firing at the same angle (powder either forward or back over the primer)? It doesn't sound like the velocity difference is enough to get you off an accuracy node, but it might be, in which case adjusting the charge down to get a match should fix it.
 
Ambient temperature was about 20 degrees warmer today. Reloder 16 is the powder. I am about 300 rounds down range with this rifle now.
 
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