SidecarFlip
Well-Known Member
Broz outta know because he fiddles with them for a living. I'm just a hobbyist.
Sounds like a messy job to me. I guess I could fixture the receiver and indicate the parallelism and height differential between the adjacent bases as it pertains to post mounting, Right now I use the 'feel method' to sense any misalignment and lap off the high spots using an appropriate sized bar (0.100" or 30mm) placed through both bases and some Clover fine lapping compound.... Somewhat tedious but I have lots of time. I considered mechanizing the process, tantamount to line boring, but it would be even more tedious to set up and execute.
Appropriate sized drill rod is readily available from most metals suppliers.
One thing that most consumers don't realize or take into account is that metal, any metal, is always moving. Not a lot, but it continuously moves with temperature changes and even the way a particular part is packaged can adversely effect the trueness and parallelism over it's length and cross axis. That includes the rings and the optic itself.
It has to do with grain structure and a whole bunch of things technical and not germane here.
It becomes apparent when using precision measuring instruments that indicate in tenths (0.0001) or better, something I deal with in the shop.
2 good examples come to mind. One is bench grinding wheels and surface grinding wheels (for me). never purchase a grinding wheel that's laying on it's side, on the shelf, in a store, because gravity has deformed it, they must be stored on end.
The second example is cylinder liners for diesel engines. They also must be stored vertically because, if stored on their side, gravity will cause the bore to become oval.
Gravity affects everything metal and non metal. You could purchase a rail thats been packaged with it's center point resting on some high point in the packaging and laying flat on a shelf for a period of time and that rail will be higher in the center than it is on the ends and that will show up in ring misalignment and the misalignment won't be consistent because the the center point in the packaging may be or not be centered on the rail in the first place.
In other words, any rail can be in misalignment prior to mounting and the receiver's metal can also be misaligned, causing even more problems, problems that can become apparent when shooting extreme long range versus a hundred yards or so. The longer the shot, the more critical alignment of the respective components becomes and the more 'metal movement' comes into play.
Every part coming off the CNC is created equal or at least as equal as the machine can make it within it's designed accuracy parameters. As the part ages and sits, metal movement can and will change the initial dimensions and can adversely impact your end use, which is why lapping or seating the rings in respect to the optic is a good idea.
Remove as much misalignment as possible before clamping the assemblies together and while on the subject, it's important to adhere to each respective manufacturers torque specification for respective components. Over torquing fasteners not only increases the chance of breakage, it will deform the part or assembly that's being secured by the fasteners in the first place, so no matter how carefully you try to correct misalignment, cranking down on the respective fasteners will negate and possibly amplify the misalignment you just spent a gob of time trying to remove......
I adhere to the above procedures all the time in my shop. It has nothing to do with firearms but is just accepted shop practice when working with accuracy in metal parts.
Sounds like a messy job to me. I guess I could fixture the receiver and indicate the parallelism and height differential between the adjacent bases as it pertains to post mounting, Right now I use the 'feel method' to sense any misalignment and lap off the high spots using an appropriate sized bar (0.100" or 30mm) placed through both bases and some Clover fine lapping compound.... Somewhat tedious but I have lots of time. I considered mechanizing the process, tantamount to line boring, but it would be even more tedious to set up and execute.
Appropriate sized drill rod is readily available from most metals suppliers.
One thing that most consumers don't realize or take into account is that metal, any metal, is always moving. Not a lot, but it continuously moves with temperature changes and even the way a particular part is packaged can adversely effect the trueness and parallelism over it's length and cross axis. That includes the rings and the optic itself.
It has to do with grain structure and a whole bunch of things technical and not germane here.
It becomes apparent when using precision measuring instruments that indicate in tenths (0.0001) or better, something I deal with in the shop.
2 good examples come to mind. One is bench grinding wheels and surface grinding wheels (for me). never purchase a grinding wheel that's laying on it's side, on the shelf, in a store, because gravity has deformed it, they must be stored on end.
The second example is cylinder liners for diesel engines. They also must be stored vertically because, if stored on their side, gravity will cause the bore to become oval.
Gravity affects everything metal and non metal. You could purchase a rail thats been packaged with it's center point resting on some high point in the packaging and laying flat on a shelf for a period of time and that rail will be higher in the center than it is on the ends and that will show up in ring misalignment and the misalignment won't be consistent because the the center point in the packaging may be or not be centered on the rail in the first place.
In other words, any rail can be in misalignment prior to mounting and the receiver's metal can also be misaligned, causing even more problems, problems that can become apparent when shooting extreme long range versus a hundred yards or so. The longer the shot, the more critical alignment of the respective components becomes and the more 'metal movement' comes into play.
Every part coming off the CNC is created equal or at least as equal as the machine can make it within it's designed accuracy parameters. As the part ages and sits, metal movement can and will change the initial dimensions and can adversely impact your end use, which is why lapping or seating the rings in respect to the optic is a good idea.
Remove as much misalignment as possible before clamping the assemblies together and while on the subject, it's important to adhere to each respective manufacturers torque specification for respective components. Over torquing fasteners not only increases the chance of breakage, it will deform the part or assembly that's being secured by the fasteners in the first place, so no matter how carefully you try to correct misalignment, cranking down on the respective fasteners will negate and possibly amplify the misalignment you just spent a gob of time trying to remove......
I adhere to the above procedures all the time in my shop. It has nothing to do with firearms but is just accepted shop practice when working with accuracy in metal parts.
