6.5 Creedmoor Headspace confusion?!

[sierrawilderness]

I'm working on reloading 6.5 Creedmoor. After looking at saami specs and hornady book... Numbers don't seem to match up.

All my factory ammo when using the hornady compactor headspace tool seems to measure the headspace using the .400 D gauge at 1.531 - 1.533 - knowing Saami isn't that.. I'm guessing the gauge is more of a reference vs an exact measurement?! Just making sure I'm not going insane or something is off.. My calipers are zeroed with with the comparator on. Any info or encouragement is much appreciated!

 

[memilanuk]

There's a reason why they're called "comparators" - they 'compare' *relative* measurements. Unfired vs fired. Fired vs sized. Etc. Etc. Not 'absolute' values.

Add to that, the SAAMI number is for if you had a hard sharp edge that met *exactly* at the 0.400" diameter on the shoulder. Look at the inside edge of your comparator insert - I'd wager it's not a hard sharp corner. Probably more of a radius or chamfer - because it's aluminum, and a hard corner on an aluminum tool meant for consumers (you and I) isn't going to be very durable. That's going to affect how it reads, slightly. It still works just fine as a comparator.

Unless you have some reason to think the chamber is out of spec, relative to SAAMI, don't worry about so much - or at all - what the comparator reads on the headspace gauge. Put the gauge away - it's for checking your barrel, not your brass, 99% of the time. Zero your calipers with the comparator installed, then check a fired, deprimed case. Adjust your sizing die to bump that shoulder ~3 thou. Check occasionally. Move on.

 

[straightshooter1]

I'm working on reloading 6.5 Creedmoor. After looking at saami specs and hornady book... Numbers don't seem to match up.

All my factory ammo when using the hornady compactor headspace tool seems to measure the headspace using the .400 D gauge at 1.531 - 1.533 - knowing Saami isn't that.. I'm guessing the gauge is more of a reference vs an exact measurement?! Just making sure I'm not going insane or something is off.. My calipers are zeroed with with the comparator on. Any info or encouragement is much appreciated!

Yes.

As mentioned the previous post, it's a "comparator". . . not a precision measuring instrument. It helps measure continuity between your brass and how much you die moves the shoulder or not.

 

[918v]

The problem with 6.5cm saami headspace and factory brass is you can end up with .015” of shoulder length growth and still be in spec. What I like to do with new brass (if it is real short) is run it through a 308 FL die prior to loading. This will pop the shoulder forward and keep the case head against the bolt face for the initial firing. It does not harm accuracy and results in longer case life.

 

[sierrawilderness]

There's a reason why they're called "comparators" - they 'compare' *relative* measurements. Unfired vs fired. Fired vs sized. Etc. Etc. Not 'absolute' values.

Add to that, the SAAMI number is for if you had a hard sharp edge that met *exactly* at the 0.400" diameter on the shoulder. Look at the inside edge of your comparator insert - I'd wager it's not a hard sharp corner. Probably more of a radius or chamfer - because it's aluminum, and a hard corner on an aluminum tool meant for consumers (you and I) isn't going to be very durable. That's going to affect how it reads, slightly. It still works just fine as a comparator.

Unless you have some reason to think the chamber is out of spec, relative to SAAMI, don't worry about so much - or at all - what the comparator reads on the headspace gauge. Put the gauge away - it's for checking your barrel, not your brass, 99% of the time. Zero your calipers with the comparator installed, then check a fired, deprimed case. Adjust your sizing die to bump that shoulder ~3 thou. Check occasionally. Move on.

Thank you! Its my first time reloading a rifle round. I was using the factory ammo to compare to fired round. The federal shoots sub moa out of my Christensen, so I wanted to make sure I was duplicating something that works but staying in spec. My rifle shoots amazing. Thank you for this! Just wanted to make sure I was in the right track!

 

[TheJammar]

You can also use the C .375 insert. Doesn’t really matter since it is a comparator

Lock‑N‑Load® Headspace Comparator & Anvil Base Kit - Hornady Manufacturing, Inc

Lock‑N‑Load® Headspace Comparator & Anvil Base Kit Lock-N-Load® Headspace Comparator The Lock-N-Load® Headspace Comparator extends brass life, improves accuracy, and enhances safety. The gauge measures...

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