Sierra Heavy TMK 6MM Testing

[khuber84]

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Post in thread 'Sierra Heavy TMK 6MM Testing'

Dec 21, 2025

This is in your Seekins 6 CM correct? If so, SAAMI freebore of .183.

Seated at .080 off, where does this put the boat tail to shoulder junction in the case?
Wondering if a longer fb, such as the PVA Standard (.210) might optimize these even more.

Any chance you could take a photo of a loaded round with a bullet lined up next to it?

@khuber84 I think a short 6 CM slinging these 117’s at 2800-2850 would be absolutely phenomenal.

Apologies for the terrible lighting. This is seated at a .085" jump, but this barrel also has over 1400 rounds on it. My typical...

• Carl Ross

• 

I did. There was no COAL listed. I figure 1400RDS of 6cm would likely have 40-70k throat erosion depending on how it was ran, powder used and what not.

 

[Carl Ross]

I did. There was no COAL listed. I figure 1400RDS of 6cm would likely have 40-70k throat erosion depending on how it was ran, powder used and what not.

It's 2.900" give or take. H4350 is the only powder, mostly pedestrian loads, sometimes ran hot-ish.

 

[khuber84]

It's 2.900" give or take. H4350 is the only powder, mostly pedestrian loads, sometimes ran hot-ish.

Thanks Carl! Appreciate you getting that info!

 

[PathFinder]

Testing on paper with the 243 Improved today at 500. Similar results between the three overall, with a little BC difference showing up.

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