Proper Headspacing - resistance

With a steel Go-Gage you can probably FEEL a half thousandths change in head space.
Sounds like you are good to go, shooting Go-Gages
How about factory ammo or new brass?

Put a piece of scotch tape on the back of the go gauge, it doesn’t close at all. Sounds about perfect.

+.0015” over “go” is a good place on a tightened barrel. From what you’ve saying, you’re closer to .000”.

Too tight you can run into trouble with some of your brass

Could just be the ejector you are feeling. Sounds like my kind of chamber honestly but who makes the gauges? As @spife7980 said, you can put a layer of scotch tape on the back and see if that keeps it from closing. If so it's good

Woolsocks said:

Well, it doesn’t close on factory brass, so I guess it’s too tight. Try try again.

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It doesn't close on factory brass? What brass is it? Virgin lapua? That does sound concerning.

Woolsocks said:

JGS gauges, nosler brass (new, not fired)

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So I assume it doesn't close with a piece of tape on the back of the gauge then too. Sounds tight then.... call the smith and I'm sure he will take care of it. Those gauges should be good and if it's also not closing on new nosler then it's likely a little tight.

I did have some gauges that were a little off but they were ptg and I won't even get into that

Similar boat as the OP, but I was wondering about the no-go gauge. PVA variable shoulder in an Archemdies action. Smooth on the Go gauge, and doesn’t close with the no-go, but it doesn’t really engage at all?

Forster 6.5C gauges.

I bought this a few years ago, and just got around to putting it together now, so shaking the cobwebs off about it,

ETA. Should have mentioned I’m using the BARLOC barrel system where you head-space off the GO. I re-did it with a layer of tape on the go- gauge. Still works without the tape on it, and now the no-go gage just every so slightly will start to engage. Does this mean that I have a tight chamber? Should I do it two layers of tape-that’s the right way to shift it if I am tight. Or maybe I have a long No-GO?

Plus, the Archemedies doesn’t have a bolt face ejector? Do I need to take out the extractor?

Sounds like you have given yourself a 0.0000 chamber, you want to feel the handle go down in contact with the GO but not need any force to do so. The bolt should not close on the NO GO and if you have a FIELD guarge then it is must not close on it.
The Ideal is GO +0.001 for high precision types to ensure there is a minimal tolerance for any error rather than have an undersized chamber and have major problems with using the firearm - had a chamber done specification minimal tight chamber like normal with a 95 Palma and so badly done that brand new Lapua minimum cartridge would only just chamber and with hard extraction come out smaller than before firing!
Went back to the gunsmith and he modified the Barnard P bolt to fix it and then it was new brass only as the face and lugs was on the piss, and grouped +/- 1.25MoA from PoA, and still unable to extract. In desperate need to get it fixed went back to my normal GS (sports politics) with his 95 Palma reamer and removed 0.002 of material from the chamber wall and extraction issue resolved but not the grouping - fixed by going down the road to Barnard and having a new bolt factory lapped in and the problem batches of ammo grouped 0.25MoA with evey batch randomly fired into it having the same PoI

You shouldn't have to take the extractor out for this operation. But, I would normally recommend taking the firing pin assembly (cocking piece, etc.) out so that you don't have that spring pressure masking the feel.

I realize that the bolt on the Archimedes is a little bit different and that takedown isn't quite as straightforward as with others. But I sincerely believe that in order to get the best fit, you really need to not have that spring pressure masking the feel.

Personally, with a 'variable headspace' setup (barrel nut, in my case) I go for a *very* slight amount of drag/resistance when closing/lifting the bolt on the GO gauge, and then when I snug up the nut it takes up any slack in the threads. At that point the bolt should close/lift smoothly, and won't close on the NO-GO gauge.

How much slack there is to take up can vary considerably, from a factory Savage action with a factory barrel nut (quite a bit) to say, my Origin action with a NSS precision machined nut (not very much at all). So that's why I kind of obsess over being able to *feel* as much as possible through the installation process.

I recently installed a Criterion 6CM barrel on my Origin action. Using the process as described above, the bolt closed freely on factory loaded ammo, and the fired cases came out measuring 1-1.5 thou over the headspace of the GO gauge. I consider that a success

How much of that translates to a bar-loc setup, I honestly cannot say. Hopefully it helps some.

The Archimedies is a controlled feed round so the extractor shouldn’t really have a role in trying to get headspace. The Archemidies (I’ll eventually spell it right) has that camming(?) or spring loaded bolt ‘arm’(?) knob, so I’m not sure on the ‘feel’ aspect?

Wouldn’t getting any kind of drag on the GO gauge be sign of a tight chamber.

Am I right that having the no-go gauge not close at all is a sign of a tight chamber?

It takes a round with the same effort as the GO gauge. This is my first ‘engineered’ and tricked out action, so ‘feel’ is a vague term for me.

FromMyColdDeadHand said:

The Archimedies is a controlled feed round so the extractor shouldn’t really have a role in trying to get headspace. The Archemidies (I’ll eventually spell it right) has that camming(?) or spring loaded bolt ‘arm’(?) knob, so I’m not sure on the ‘feel’ aspect?

Wouldn’t getting any kind of drag on the GO gauge be sign of a tight chamber.

Am I right that having the no-go gauge not close at all is a sign of a tight chamber?

It takes a round with the same effort as the GO gauge. This is my first ‘engineered’ and tricked out action, so ‘feel’ is a vague term for me.

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I prefer to do any "feel" testing with the firing pin and spring removed. Extractor is irrelevant on just about any bolt action, and the ejector in the Archimedes won't affect anything either (as opposed to a R700-style plunger ejector). Getting the firing pin out of an Archimedes bolt is a bit of a process, but I do it every time I'm checking headspace. It's not technically mandatory, closing on an empty chamber should feel the same as closing on the GO and the NO-GO shouldn't close; however, it's a lot more obvious what's going on with all the guts out of the bolt.

Not sure what you mean by "engage," but I'm guessing you're saying you get a bit of movement down on the bolt handle but can't close the bolt all the way; because the Archimedes doesn't do any primary extraction, I'd lean towards having zero bolt movement, but it's not a big deal if you get a bit before it locks up.

For both you and OP, there are upsides and downsides to a "tight" (short) chamber, but as OP is seeing, it can make some factory brass unusable without modification. That's not a place I want to be, so I'd rather have a chamber that almost closes on a NO-GO than one that's generating a bit of friction on a GO gauge. That'll provide better flexibility on brass/ammo. If you have a chamber that's too short for factory brass, you end up having to address that in one of several ways; the simplest is probably to put a few thousandths of shim stock in your shellholder to push the shoulder back shorter than SAAMI, but that's really not ideal.

FromMyColdDeadHand said:

The Archimedes is a controlled feed round so the extractor shouldn’t really have a role in trying to get headspace.

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You were the one who suggested removing the extractor, not me.

FromMyColdDeadHand said:

The Archimedes has that camming(?) or spring loaded bolt ‘arm’(?) knob, so I’m not sure on the ‘feel’ aspect?

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As I understand it (don't have one in hand, personally) the feature you're referring to only really comes into play when opening the bolt and needing primary extraction ie if a case is sticking in the chamber. *Usually* that's more a function of radial case expansion, like at the case web / 0.200" line, than the shoulder (headspace), so it shouldn't get involved in what we're doing here. But the cocking piece and firing pin spring do, so like I said, remove them for the testing / fitting process.

FromMyColdDeadHand said:

Wouldn’t getting any kind of drag on the GO gauge be sign of a tight chamber.

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Yes... and no. You said you're using a variable headspace barrel, where *you* control the headspace. If you can't close the bolt on the GO gauge, then yes, it's too tight. If you can, it's fine. I was suggesting starting with a bit of drag / interference fit, which would be relieved as one tightens the barrel nut, like I described. If you don't have a nut, then that may not apply. Also like I mentioned above.

FromMyColdDeadHand said:

Am I right that having the no-go gauge not close at all is a sign of a tight chamber?

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Re-read that again, and ask yourself if that makes *any* sense

FromMyColdDeadHand said:

It takes a round with the same effort as the GO gauge. This is my first ‘engineered’ and tricked out action, so ‘feel’ is a vague term for me.

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If it closes on a go gauge, closes on the loaded rounds okay, and ***DOES NOT*** close on the no-go gauges, then it's fine. Or at least 'safe'. Most people 'aim' for the tighter end of the range between 'go' and 'no-go', probably out of habit. If it's the only gun you have in that caliber, then it really doesn't matter.

Honestly, it sounds like you need to find someone local to you to walk you through the process in person at least once. You've got a new-to-you action that is just a little bit different than normal, and you've got a barrel install method (bar-loc) that is just a little bit different from what most people use. And it's apparently your first time messing with any of this.

Thanks for all the input and time. If it were a stock 700, I would have just run the gauges and called it good, or if it were a ‘full’ prefit I would have just torqued it and run the gauges and called it good. It’s having that extra degree of freedom of having to/can adjust the headspace. That degree of freedom gets in my head- as in is it set to optimal? And beyond that, I like getting ‘failures’ in tests so that I know that I’m not getting false negatives.

Like I said, this was a project gun that got put to the side. It’s actually a back-up gun for class I’m taking, so I have some time and someone to look over it for me before that.