Knutz and boltz:
Unless an action has been used as a chock block for a commercial airliner or as a crowbar on an oil derrek chances are good the receiver bore is pretty straight. Since my ground tapered arbor fits tight it matters little to me because I datum everything off bore CL anyways. It can be out basically as much as it wants. I seriously don't care because when I'm done all my surfaces are going to be square, parallel, and concentric to it anyway.
As far as bolt slop goes. Yes in a perfect world it is/would be nice to have a minimal tolerance fit between the OD of the bolt and ID of the receiver bore. I have long advocated the almost zero tolerance/slip fit of a Nesika or Borden action just for this reason. (Borden bump feature is what I mean specifically)
In practice. Sit down with a trig cheat sheet or a CAD program and draw a tube with a .704" bore. Stuff a .695" OD stick through the center of it. Now load one side to the point of contact. You end up with .0045" of deflection from theoretical centerline. Now do the math.
A standard length Remington 700 bolt measures 4.400" from the lug surface to the front edge of the handle. When in battery with a loaded striker spring I have no doubt the cocking piece is pushing the bolt vertically as it tries to get over the trigger sear. It'll do this until the 12 o clock tangent of the bolt body contacts the 12 o clock tangent of the receiver bore. This means that only the lower locking lug is in contact with the receiver. That angle of deflection measures out to be .0586 degrees.
The half dozen Remington bolts I have floating around here all measure around .695" +/- .0015" so I'm feeling pretty good with my figures.
The "swept arc" of the locking lugs is around .980"
.980" - .695" ='s .290" Now divide that by 2. It's .145" that is the distance of the lug feature from the outside radius of the bolt body to the outside radius of the lugs. If you figure an angular deflection of that .0586 degrees referenced earlier in my little sermon you'll find that the "sloppy fit" between the receiver lug surface to the bolt lug surface is (drum roll please)
.00015" To put this in perspective gents, most high quality thimble micrometers are incapable of measuring this kind of dimension with any kind of reliable repeatability.
Now, it seems reasonable to me that when a 50,000 CUP cartridge lights its boiler room that .180955736847" square inches of cartridge rim (figured off a .480 cartridge case head OD) is going to have little issue with pushing that upper bolt lug the .00015" to square things up.
And all from a "chitty" pawn shop Remington 700.
My proof is you go to the firing lines of Camp Perry or any other Marquee NRA highpower match. There are dozens of Remmy 700's on the firing line and almost none of them have the little bushings epoxied on the bolt body that folks seem to rave about.
I realize benchrest guys are a very particular sort. Be that as it may I feel pretty good stating that the better shooters have realized long ago that 90% of a guns accuracy comes from a great barrel, careful ammunition preparation, and PRACTICE.
The other 10% is receiver, bedding, a crisp trigger, a good set of optics, and just dumb luck (meaning you beat the wind that day)
Hope this was at least entertaining if not even a little educational.
Cheers and all the best,
Chad
Chad Dixon
Gunmaker
LongRifles, Inc.