Makes me wonder what their tolerances are. Also, I've heard that they need to be made with more slop in them to allow for the dissimilar metals (steel bolt).
Tolerances are likely good enough you would have a hard time spotting any issues with your $25 digital caliper. I don't know for a fact, but my guess is that when you machine precision actions for a living, you nail down tooling, fixturing, and speeds/feeds to mitigate the PITA as much as possible. Tighter is not always better. You see the same issue with certain stainless actions that are so tight they can barely be cerakoted (.001" thick layer--- 1/6th the thickness of a sheet of paper) and still function-- introduce ANY dirt/dust and they choke and become a bear to cycle.
More slop in them (to a point) is ideal for any action IMO. Think of it this way, a Savage with a new match grade barrel and proper load dev. shoots sub 1/2 MOA. You don't get any more loosey goosey, sloppy, rattly than that besides like a Mossberg, or a 1945 made Arisaka... But the fuckers still shoot.
Look at the ARC M5-- IMO the best custom action out there for most purposes unless you're stuck on AW magazines, but it's got like .010-.015" clearance on most of the bolt body relative to the action bore. There's a taper at the back end to tighten things up a little as the bolt goes into battery. But what you've got to remember is that there are several geometries at play at once here. It's not just "Oh well the bolt is smaller than the action so there's play"... No.. There are lugs butting up against recesses under the spring pressure of the FP spring, there is a double-tapered cartridge seated centered in the chamber with typically .001-.002" of allowable headspace play (if everything is clean).... Not near as much room for movement as a guy might imagine. And for the most part, what does happen, even on rifles loose enough for there to be movement with the bolt locked down on a loaded round--- largely does not matter. Savages, old WWI and WWII mausers, enfields... pretty much every action shoots great with a match grade barrel...
So if you want to have a theoretical warm and fuzzy feel good because "tolerances are TIGHT" and you've convinced yourself that everything is square and that's what matters, sure. Buy I make the assumption that most people on this site are going for practical functionality/accuracy. Benchrest, and world record groups, sure get stupid tight and follow the voodoo. For 1/4-1/2 MOA, screw on a good pipe, have decent bedding/a chassis and run with it.
As far as Titanium for longevity, Don't hot rod it, and don't run it dry. It is brittle, and ultimate tensile and yield strengths are going to be lower than that of the chrome moly steels (all entirely dependent on heat treat, annealed CM can have yield strengths as low as 60ksi-- on par with cartridge brass, or with the proper heat treat cycle it can be 250+ksi).
Metals and heat treats are always a trade off between hardness/high tensile strength, and toughness, ductility, and energy absorbtion. Titanium's crystalline structure is different from most steels however, and lends itself less to ductility. i.e. it's more brittle by default (Again, depending on the steel's heat treat, an oil quench with no temper (martensite) is as strong/hard as steel gets, but uselessly brittle).
Anyway, without typing a fucking novel here on material properties... The main take away is that the stuff likes to gall more than CM steel, and probably more than the grades of SS used in rifle actions, and it's brittle, and the yield/tensile strengths are probably lower than those of steel. Obviously they can handle full-power loads-- where what I'm talking about comes into play is the failure mode in the event of over-pressure. Ti is going to fail at a lower pressure, and be more prone to crack or fragment instead of having lug setback or having the action bend/warp and contain the excessive pressures. You have to go well over the published loads to get there, not trying to scare anyone.
So stay sane with it, and keep it lubed, and it will out last you.
