Headspace Gauge

mikemo4032

Active Member
Joined
Nov 24, 2014
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36
I have two SA Defiance Devient actions that are both shooting 6mm. I have accumulated several 6mm barrels and most are chambered in 6x47 lapua. The barrels have been chambered by different Smith's and I want to try and fit them without regard to the original action they were fitted to.
Is headspace my only consideration?
Do I use the 6.5x47 go/no go gauges to check headspace between the two actions? Thanks!
 

tobnpr

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May 30, 2013
Messages
127
Same datum length on the two, so the gauges for the 6.5 would be fine for the 6.

That's the easy question.
I'm unclear about the "barrels being chambered by different smiths" part.
Were they fitted to your Deviant actions originally and you just don't know which went with which, or are they from some other action(s) entirely?
 

mikemo4032

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Nov 24, 2014
Messages
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Same datum length on the two, so the gauges for the 6.5 would be fine for the 6.

That's the easy question.
I'm unclear about the "barrels being chambered by different smiths" part.
Were they fitted to your Deviant actions originally and you just don't know which went with which, or are they from some other action(s) entirely?
No, all the barrels were chambered and fit for one or the other Defiance action. It would be nice if could switch barrels between the two actions after checking for head space. If the head space is out of spec, I'll have to get my current smith to adjust for correct head space.
 

tobnpr

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May 30, 2013
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Still a bit unclear as to your objective, but sounds like you're just trying to figure out which barrels were fitted to which actions.

It is possible that barrels could headspace within tolerances of the gauges on both receivers- but you'd still want to know which has the tightest clearance beyond "go" if that happens. IOW- if the same barrel passes "go" and "no go" on both receivers, it's almost certain to have more clearance on one vs. the other. Something like go + .001 on the receiver it was originally fitted to- but maybe go + .004 on the other.

You can check by adding a layer of cellophane packing tape (usually around .003- but best to mike it) trimmed to fit the back of the go gauge. You want your bolt stripped (spring, ejector) so there is no resistance, handle should fall with little to no resistance on go gauge. Add the tape, handle should not fall.
 

mikemo4032

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Nov 24, 2014
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Yes, That is exactly what and why I wanted to know about using head space gauges. I've always just left that to the Smith, but with several barrels on hand I thought it may be interesting switch them between different rifles to see if they shoot differently. Thanks for your help.
 

tobnpr

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May 30, 2013
Messages
127
I believe the thread lead is at the exact same location on those actions so it may not be much of a factor; otherwise might headspace OK, but the barrel engraving could be "off" depending on how it clocks.

I'm sure you know this, so just sayin'- barrels must be properly torqued, not hand tight, to check headspace.

Let us know how it works out.
 

Clay Target Guy

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Jun 5, 2013
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On a good quality action like that, I would guess that the distance from the face of the action to the bolt face would be the same (or within .001). This will also play a roll in the switching back and forth.
Having said that, I like the idea
 

mikemo4032

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Nov 24, 2014
Messages
36
Thanks for the reply,
My go/no goes get here this week. I am with you on the two actions being close. But... you can't assume right? And it's not like I don't have time on my hands to try different barrels and set ups. I'll post what I find, hopefully later this week or next.
 

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