It's always a nervous time when you first use a new chamber reamer.... They seem to get smaller through the polishing, hardening and repolishing, and I'l always wondering if it will cut the chamber to the right diameter.... When I set up to cut the chamber in my 6mm barrel today and starting advancing the reamer, it went so easy I thought "carp, it's too small".... I cut the leade into the barrel about 1/4", and then pulled it out.... To my surprise, and delight, I found that it cut better than any reamer I had ever made before, and the little channel between the flutes that I had filled with oil had a nice pile of shavings sitting in it....
Usually you can "feel" quite a bit of resistance on the handwheel on the tailstock as you feed the reamer in, the barrel gets warm, and the shavings are not much more than dust size.... Not so with this reamer, the shavings were like little needles, about 1/16" long and 0.005" in diameter or so.... I could actually feel the "bump-bump-bump" as each flute hit the rifling lands and slowly carved them away.... I don't know why this one is so much better.... but I hope they all come out like this from now on.... It may be that I honed it just right.... I know I will try the same honing technique on another reamer the next time, to see if that was the difference.... I sure hope so, this one cut a beautiful chamber in short order.... Here are the three 6mm bullets I used to set the length....
Left to Right are the 63 gr. NOE 245-64 FN.... the 61 gr. Bowman by Arsenal.... and the 73 gr. NOE 245-74 FN.... The 63 gr. is a shortened version of the 73 gr., with the gas check shank missing.... These two bullets are "bore riders", and you can see the shiny spots on the nose of the 73 gr. where it rubbed along the lands.... The front driving band is engraved to about half the rifling depth, as it is sitting in about the middle of the leade.... There are very slight marks on the rear band from the back of the leade, and about the same on the back band of the Bowman (which is a copy of the Lyman 257420, scaled down to 6mm).... The middle band of the Bowman is engraved about half depth, and the very front of the front band is just about full rifling depth, which is what I aim for.... The 63 gr. barely touches the leade with the front band, but if you push slowly on it, you can feel that it is seated firmly against it, but just enough to leave tiny marks.... There are some tiny polished spots on the nose, just at the back of the ogive, where it is just sitting on the lands.... I'm very pleased with the way this chamber came out.... In terms of size, a bullet sized to 0.243" slides in easily.... but one sized to 0.244" requires a bit of a push.... so the chamber size is perfect.... This reamer is a KEEPER !!!
This afternoon I set up the receivers in my milling attachment in the lathe, and adjusted it so that it cut a 20 MOA angle into the top of the Dovetails.... That works out to only about 1mm (0.040") less height at the front of the dovetail than at the rear.... but should put the POI at about optical center of the scope at 100 yards.... I then machined the dovetails into the sides of the raised portions on the receivers.... I took a bunch of photos of the two receivers with the dovetails, and had trouble with reflections hiding the angle of the dovetails.... but you can just about see that in the photo below (with a little imagination)....
If you look closely, you will see that at the front of the dovetail, the bottom of the cutter ran along the top edge of the bevel on the corners of the receiver.... but at the back of the dovetail the cutter left a ridge 1mm above the top of the bevel.... It's hard to believe that is all the elevation angle required of the barrel, relative to the scope, to put you on target at 100 yards.... but 0.040" in 6" works out to 24" at 100 yards (0.040 x 100 x 3 x 12/6).... When you mount the scope you can barely see the angle, if you didn't know it was there you would never notice it....
Bob