There's been a fair amount of recent chatter regarding the validity of working a receiver over.
This morning I started on a new job. I've got a Remmy 700 that has a scope base that doesn't fit quite right and the cst wants the base holes opened to 8-40.
Through the process of setting the receiver up to machine the hole locations (notice I didn't say drill) I decided to check a few things that <span style="font-weight: bold">normally I don't concern myself with since I machine them anyway regardless.. </span>
First step was to clamp the action in the vise and indicate to center based on the <span style="font-weight: bold"><span style="font-style: italic">outside</span></span> of the action. Basically its a simple process that involves bouncing the edge finder off both the fixed and moving mill vise jaws as they are a qualified surface, ground parallel, etc. From there I just split the difference and positioned the table to my center position. With a "wiggler" tool over the existing base hole I then made a simple visual reference.
The result was proof positive that the base hole is not on center with relation to the OD of the action. As the photo shows, the wiggler probe is crowding on the left side of the base hole.
Next step:
<span style="font-style: italic"><span style="font-weight: bold">Since we rarely care about the outside of the action when tuning things up,</span></span> <span style="font-weight: bold">I installed my centering mandrel into the Id bore and repeated the process all over again just to see what the differences were. With the wiggler over the existing holes it again shows the location out of clock position slightly. Tough to see in this photo but again its favoring the left side of the action.</span>
What this tells me:
In this particular case the OD and ID bore are pretty dern close to one another in terms of concentricity. I didn't measure it (because it has no bearing in this exercise) but the simple visual tells me they are probably within .005" of each other.
The scope base holes however are out of <span style="font-style: italic">clock </span>position. If viewing from the front of the action they are slightly behind 12 o clock. (11:58-ish. . .)
Probably not enough to hurt anything but again it's not "right". No worries since I machine my holes using a .125" endmill and just circular interpolate a round hole instead of hoping that a drill will run to the new center (it won't, it'll just follow the existing hole)
Now I gauge the hole using a .136" pin gauge to ensure my inside diameter is correct before I go blazing away with cutting threads for the new base screws.
Nothing really alarming, Just kinda emphasizes the fact that these actions, while pretty good overall, are in fact mass produced and its rather challenging to replicate perfection over and over again while still maintaining a price point that consumers will tolerate.
Enjoy your Saturday gents.
-C
This morning I started on a new job. I've got a Remmy 700 that has a scope base that doesn't fit quite right and the cst wants the base holes opened to 8-40.
Through the process of setting the receiver up to machine the hole locations (notice I didn't say drill) I decided to check a few things that <span style="font-weight: bold">normally I don't concern myself with since I machine them anyway regardless.. </span>
First step was to clamp the action in the vise and indicate to center based on the <span style="font-weight: bold"><span style="font-style: italic">outside</span></span> of the action. Basically its a simple process that involves bouncing the edge finder off both the fixed and moving mill vise jaws as they are a qualified surface, ground parallel, etc. From there I just split the difference and positioned the table to my center position. With a "wiggler" tool over the existing base hole I then made a simple visual reference.
The result was proof positive that the base hole is not on center with relation to the OD of the action. As the photo shows, the wiggler probe is crowding on the left side of the base hole.
Next step:
<span style="font-style: italic"><span style="font-weight: bold">Since we rarely care about the outside of the action when tuning things up,</span></span> <span style="font-weight: bold">I installed my centering mandrel into the Id bore and repeated the process all over again just to see what the differences were. With the wiggler over the existing holes it again shows the location out of clock position slightly. Tough to see in this photo but again its favoring the left side of the action.</span>
What this tells me:
In this particular case the OD and ID bore are pretty dern close to one another in terms of concentricity. I didn't measure it (because it has no bearing in this exercise) but the simple visual tells me they are probably within .005" of each other.
The scope base holes however are out of <span style="font-style: italic">clock </span>position. If viewing from the front of the action they are slightly behind 12 o clock. (11:58-ish. . .)
Probably not enough to hurt anything but again it's not "right". No worries since I machine my holes using a .125" endmill and just circular interpolate a round hole instead of hoping that a drill will run to the new center (it won't, it'll just follow the existing hole)
Now I gauge the hole using a .136" pin gauge to ensure my inside diameter is correct before I go blazing away with cutting threads for the new base screws.
Nothing really alarming, Just kinda emphasizes the fact that these actions, while pretty good overall, are in fact mass produced and its rather challenging to replicate perfection over and over again while still maintaining a price point that consumers will tolerate.
Enjoy your Saturday gents.
-C