SAAMI specs Hornady Headspace gauge and Lyman Caliper

Hi Everyone

This is my first post. Recently discovered this forum - it's awesome!

I have been reloading for a little while now but have always kept it pretty basic. But then I went and got a headspace gauge and a bullet comparator from Hornady and I've been measuring stuff...

My fired 6.5 x55 Norma cases have 1.768" head space. Unless I'm reading it wrong, this would leave them well outside the margin of error for SAAMI spec of 1.786" . It would also, I assume, put the chamber of my Tikka T3 well outside min SAAMI chamber head space of 1.7834. (ie inferred from the size of the fired case, I assume my chamber is just a tiny bit bigger than that.)

On the other hand, a brand new Norma unfired case measures 1.765" (ie headspace measurement) which sits nicely with my fired cases and presumed chamber headspace, but again doesn't square at all with SAAMI specs.

The SAAMI measurements are off their webpage. All the other measurements are off my Lyman mid range digital calipers. So if they are consistently under-measuring by around .02" I guess that would make sense, otherwise... ????? wtf.:wtfsmilie:

Your rifle if fitted with the factory barrel, is chambered for the 6.5x55 SE, a C.I.P. chambering. Your cases are 6.5x55 SE, again made to C.I.P. specification. It is my understanding that the 6.5x55 Swedish (i.e. SAAMI) dimensions are different from the C.I.P. (i.e. standard) dimensions and that the Fuller Pty-supplied 6.5x55 rifles that came via Australia, ended up with mismatched breech bolts because Fullers swapped some of them around to work with cheaper SAAMI spec ammo.

I suggest that you either make your query on a British site or send an email to Mr Hardy in Palmerston North, for his barrel maker to answer.

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Originally Posted by ZG47

Your rifle if fitted with the factory barrel, is chambered for the 6.5x55 SE, a C.I.P. chambering. Your cases are 6.5x55 SE, again made to C.I.P. specification. It is my understanding that the 6.5x55 Swedish (i.e. SAAMI) dimensions are different from the C.I.P. (i.e. standard) dimensions and that the Fuller Pty-supplied 6.5x55 rifles that came via Australia, ended up with mismatched breech bolts because Fullers swapped some of them around to work with cheaper SAAMI spec ammo.

I suggest that you either make your query on a British site or send an email to Mr Hardy in Palmerston North, for his barrel maker to answer.

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Wow - thanks very much for that extremely informative answer - I had no idea that CIP dimensions were actually different from SAAMI. I've made a quick comparison online and there are small differences in some dimensions, just as you say - while others are the same. Is this in fact what they mean by the Delta L problem ? Unfortunately I can't find CPI chamber dimensions/tolerances only the case (ie Wikipedia).

I'll contact Dan Hardy, thanks very much for the suggestion.

Just to clarify - do you mean that I might have a bolt which doesn't match the rest of my rifle properly? That's a disturbing thought. Should I be worried about this? It does have the same serial number, however.

Early on just after I bought the rifle I had some reloads done for me (professionally) and they were very heavy to chamber. In the end the person doing the reloading switched dies and the problem went away - again that could be the Delta L problem where the max size allowed by the die was greater than the CIP approved minimum. I'm using RCBS dies and I think they're ok with this chamber. This is a much more involved issue than I realised. I knew I shouldn't have started measuring things...

Reloading is like the more you know the less you know!

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Originally Posted by andyanimal31

Reloading is like the more you know the less you know!

Sent from my SM-G313ML using Tapatalk

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Exactly

Shit there's some high-end info there. Interesting.


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Originally Posted by WillB

do you mean that I might have a bolt which doesn't match the rest of my rifle properly? That's a disturbing thought. Should I be worried about this? It does have the same serial number, however.

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Sorry to cause confusion. I should have been more explicit. Older shooters would have realised that I was talking about the Swedish surplus Mausers that were purchased in bulk and resold, by Fullers.

Ah ok, thanks. So I have a rifle which is properly put together according to CIP specs - but these differ slightly from SAAMI specs, these two "versions" of the 6.5 x 55 even being named slightly differently. Ammunition made according to one set of specs will work and be safe in a chamber made according to the other (although there may be a heavy bolt closure) so they can be considered one calibre for practical purposes. Does that sound right?