Ian
Notorious member
The Basement Articles #7: Crafting accurate ammunition
There is a lot more to crafting truly accurate rifle ammunition with cast bullets than simply stuffing powder and bullet in the case, but basically that's it. The HOW part is the difference between a rifle that shoots so-so and one that drills holes.
This article will be heavily equipment-oriented and discuss some simple modifications often necessary to make ammunition that fits our particular guns, as well as to continue previous discussions involving just exactly what needs "fitted", and why it matters. In previous articles I discussed the aspects of static and dynamic bullet fit, how alloy plays into this during the firing cycle, and a few objectives I've found it beneficial to meet while preparing brass that fits your rifle and supports the bullet. These are some methods and tools that have helped me improve my accuracy.
Let's start with the reloading press. Maintaining concentricity and trueness in every operation while building a self-contained cartridge is essential to accurate shooting. The press used needs to have the ram square and centered with the dies, and the shell holders need to fit the ram well. Most good presses accomplish this, but some of the center-mounted turret types (Lyman, RCBS, and a few others) need to be carefully adjusted to keep the turret head from rocking under stress and literally bending things like a banana. Run the ram and shellholder up into the empty, threaded die hole and eyeball it from the top to check that the shellholder is centered on your setup.
Next, sizing dies. I'm not a brand snob, I don't care who makes the die, but it needs to do the job you need it to do, and most of them don't out of the box. I'm a fan of Lee dies because they are easily modified and cheap donors for parts. They also have a high degree of interchangeability of internal parts compared to other manufacturers who change designs and thread sizes frequently. Since the best accuracy with cast bullets is usually obtained through minimal sizing, and cast bullets are almost always considerably larger than the jacketed ones that most production dies are intended for, the neck sizing part of most full-length dies are very much too small for our needs. Through measurements of chamber casts and fired cases, case neck thickness, and through determining bullet size to be used based upon throat entrance size and other factors, one can establish just how much (or little, really) the full-length sizer die's neck needs to be enlarged to prevent unnecessary overworking of brass. In the case prep article I explained why I prefer to use customized full-length dies rather than bushing neck size or even collet dies for the majority of my work, although the other types do have their place, particularly the RCBS Gold Medal Match bushing sizer dies with the choice of body sizing, shoulder bump, or neck only die bodies. I'm only presenting the way I do this, not everyone will agree or do it my way, but I'm only attempting to outline A way that accomplishes the needed goals. Lee dies are open at the top which makes them easy to hone out with strips of emery paper wrapped around a drill shank or brass rod. I use a drill press to drive the spindles and oil the sandpaper. Once I get the neck portion honed out enough to size the brass "just" smaller than what I want it when loading (usually about .002"-.003" smaller on the ID than the bullet size), I focus on the case body portion of the die. Most standard resizing dies squeeze the body too small for best alignment in a typical rifle chamber, so I like to hone these out until a sized case just "kisses" the chamber when dropped in and has virtually no felt lateral wiggle. Modifying a sizer die to do minimal sizing will still allow you to "bump" the shoulder of a bottlenecked case back a thousandth or two from its fire-formed state without squeezing the body so much that it rattles around in the chamber like a BB in a boxcar. Every time you reload the case it will be exactly the same dimensions as last time and not get tighter and tighter in the chamber or change bolt preload over time as neck-sizing tends to do. All that leads to better consistency through the life of the brass and multiplies brass life without annealing.
There is a lot more to crafting truly accurate rifle ammunition with cast bullets than simply stuffing powder and bullet in the case, but basically that's it. The HOW part is the difference between a rifle that shoots so-so and one that drills holes.
This article will be heavily equipment-oriented and discuss some simple modifications often necessary to make ammunition that fits our particular guns, as well as to continue previous discussions involving just exactly what needs "fitted", and why it matters. In previous articles I discussed the aspects of static and dynamic bullet fit, how alloy plays into this during the firing cycle, and a few objectives I've found it beneficial to meet while preparing brass that fits your rifle and supports the bullet. These are some methods and tools that have helped me improve my accuracy.
Let's start with the reloading press. Maintaining concentricity and trueness in every operation while building a self-contained cartridge is essential to accurate shooting. The press used needs to have the ram square and centered with the dies, and the shell holders need to fit the ram well. Most good presses accomplish this, but some of the center-mounted turret types (Lyman, RCBS, and a few others) need to be carefully adjusted to keep the turret head from rocking under stress and literally bending things like a banana. Run the ram and shellholder up into the empty, threaded die hole and eyeball it from the top to check that the shellholder is centered on your setup.
Next, sizing dies. I'm not a brand snob, I don't care who makes the die, but it needs to do the job you need it to do, and most of them don't out of the box. I'm a fan of Lee dies because they are easily modified and cheap donors for parts. They also have a high degree of interchangeability of internal parts compared to other manufacturers who change designs and thread sizes frequently. Since the best accuracy with cast bullets is usually obtained through minimal sizing, and cast bullets are almost always considerably larger than the jacketed ones that most production dies are intended for, the neck sizing part of most full-length dies are very much too small for our needs. Through measurements of chamber casts and fired cases, case neck thickness, and through determining bullet size to be used based upon throat entrance size and other factors, one can establish just how much (or little, really) the full-length sizer die's neck needs to be enlarged to prevent unnecessary overworking of brass. In the case prep article I explained why I prefer to use customized full-length dies rather than bushing neck size or even collet dies for the majority of my work, although the other types do have their place, particularly the RCBS Gold Medal Match bushing sizer dies with the choice of body sizing, shoulder bump, or neck only die bodies. I'm only presenting the way I do this, not everyone will agree or do it my way, but I'm only attempting to outline A way that accomplishes the needed goals. Lee dies are open at the top which makes them easy to hone out with strips of emery paper wrapped around a drill shank or brass rod. I use a drill press to drive the spindles and oil the sandpaper. Once I get the neck portion honed out enough to size the brass "just" smaller than what I want it when loading (usually about .002"-.003" smaller on the ID than the bullet size), I focus on the case body portion of the die. Most standard resizing dies squeeze the body too small for best alignment in a typical rifle chamber, so I like to hone these out until a sized case just "kisses" the chamber when dropped in and has virtually no felt lateral wiggle. Modifying a sizer die to do minimal sizing will still allow you to "bump" the shoulder of a bottlenecked case back a thousandth or two from its fire-formed state without squeezing the body so much that it rattles around in the chamber like a BB in a boxcar. Every time you reload the case it will be exactly the same dimensions as last time and not get tighter and tighter in the chamber or change bolt preload over time as neck-sizing tends to do. All that leads to better consistency through the life of the brass and multiplies brass life without annealing.