You got snippets here and there.....for what it’s worth, here are a few more based on a lot of years, several gunsmiths, mostly good guns, every barrel configuration you ever heard of and a few you haven’t, plus a couple of great guns.
Not many people like to talk about this, a lot of it is subjective, more than a little, propriatary and among the biggest reasons CF guys steer clear of our PIA rimfires.
I’d say, most, do not own reamers. I own a couple, for various reasons, never used them although I do own my own PPC reamer, a good one will last more barrels than you’d probably ever use.
Some very accomplished smiths don’t use a reamer but cut a chamber with a boring bar.
Most match chambers for bolt guns are similar boiling down to leade angles generally between 1-3 degrees.
As Ralph alluded to chamber depth is a hotly contested arena often driven by an abundant selection in barrel configurations as to lands, traditional, ratchet( canted) and MI (minimally invasive) .
Your eyes starting to cross here ?
Chamber depths here vary from slightly into the first drive band to full engraving.....also often dictated by the barrel configuration chosen.
One of the other principle reasons you find and trust somebody that knows what they’re doing is the ability to select and evaluate a rimfire barrel blank which unfortunately can be a pretty slippery slope.
Nobody wants to drop 3 bills on a blank and get told “ it sucks” but to be truly competitive nothing beats a great barrel and some guys have gotten to the point they will buy several blanks and hope the smith finds a good one to use. Proper dimensions are critical, including a tenth or two of gradual taper towards the muzzle. It takes a while to be able to slug a barrel and evaluate what that slug(s) are saying.
Back to chambers....one well known smiths crows about having MFR’s post OAL on lots. Folks speculate but, as is often the case, with a particular bbl configuration, it may require a fairly specific chamber depth to give optimum result and if it’s set up to shoot short ammo and your next supply is .0010” longer.....your off into the weeds friend.
Also, critical to cutting the chamber and it’s depth is how long you can shoot a card before the throat begins to load up with fouling to the point of compromising accuracy. Several feel that chamber lenght is important regarding this and the last thing you need is your gun starts to fall off coming down to the final few shots.
That said, this year I personally have shot at least to some degree, five rifles chambered by two well know smiths. I have also begun shooting Lapua, if for no other reason than to test for myself and I would say all of those guns, each with entirely different barrel configurations did OK. The last year or so I have had a lot going on but I did shoot a couple bigger matches with tough competitors and the guns shot well....anything bad was generally on me.
All of these guns have what I would call, “ middle of the road” chambers and they handle both ELEY and Lapua OK , as well as long and short ELEY. I still have a couple lots of some of the 2012-2013 ELEY which was exceptional but varies by10 thou OAL which, other than firmer chambering feel, have shot very well.
The purpose for this, probably long winded, post is to answer a few questions but make folks remember that getting answers is helpful but making sure what the important questions are......... infinately more so and far tougher for newbies.