Reloading: Keep it consistent
- By Wheelwrite
- 0 Comments
- Last updated: 01/07/2019
Successful handloading is a form of juggling. We take a significant number of variables and attempt to rationalise them into a single, consistent product; our ultimate cartridge. The challenge is to correctly assess the importance each has on this process. Let’s start by identifying the variables, in no particular order. Cases; stiffness, capacity, fit and cleanliness. Propellant variation and charge consistency. Primer performance and pocket condition. Bullet weight, neck tension and seating depth. Die cleanliness and settings.
All the cases in the batch must be of the same headstamp, lot number and working history. If we’re using them in a single chamber, the once-fired brass should only require neck-sizing. However, for improved performance, we need to ensure that they all have the same capacity. Making the assumption that the outside dimensions are more or less identical, any variation in weight must reflect a change in capacity. This requires the de-primed and cleaned brass to be trimmed to length and then batch-weighed and sorted by variations of more than 2 to 3-grains.
A significant refinement can be had by actually establishing the Water Case Capacity (WCC). Indeed, for use with reloading software, such as QuickLoad, this will form part of the pressure calculations. Here, the primer is left in the cleaned and trimmed brass. The case is weighed, then distilled water is added until the meniscus is on the neck edge, then re-weighed and the capacity can then be established. By example, a 1-grain variation of a commercial .223 case can represent a potential spread of nearly 5,000 psi (that’s a staggering 9% of the maximum for the calibre), thereby taking a potentially safe load well beyond the SAAMI spec. That’s a significant variable.
Cases work-harden with use and can be sorted by annealing (de-hardening). Machines such as the AMP (Annealing Made Perfect) can restore the factory condition. Fit refers to relationship between the cartridge and the chamber. As the case grows with use, so this will change, impacting upon the headspace. Even with all other things equal, this can vary throughout a batch. Dimensional and physical fit checks will reveal the need for corrective measures, such as full-length resizing and/or neck bumping, as well as trimming. Propellant consistency must NOT be taken for granted; and, whilst the name on the container may stay the same, the contents may NOT.
I’ve previously used the example of 4227. There are two branded versions, Hodgdon and IMR. To my knowledge, over time, it has been made in at least four different factories across the globe. Each iteration has had different performance characteristics, and that is without the lot-to-lot variations from an individual manufacturer. Just because 22.4 grains was your Holy Grail with the original version, does not mean it still is! Always begin by reworking a load when starting a newly numbered batch, or manufacturing source of your chosen fuel.
Weighing variables present themselves in two ways, the first is the volumetric. As a simple demo; pour uncooked long-grain rice (to simulate ball powder) into a cup until it is level with the rim. Now pour corn flakes (simulates a coarse flake powder) into the another one until level with the rim. Pick up both cups and tap the bottoms to settle the contents. The point it makes is that coarse flake powder will continue to compact in the powder measure for dozens of cycles and again when you top up. For a set volume, it means that each thrown charge will get heavier as the packed density increases. The solution is to throw a charge slightly below that required and trickle the last few tenths. Slow but reliable. The second is an issue with many older electronic scales, whereby the averaging software fails to correctly deal with the addition of slowly trickled powder, leading to errors.
The performance impact of changes in charge weight is a matter of percentages. Let’s make a reasonable guess that the greatest error of a thrown charge from a mechanical scale is going to be +/- 0.2-grain. If the weight is 50-grains, it represents 0.8%, whereas for a charge weight of just 5-grains it becomes a massive 8%.
Primers and pockets are often overlooked. The pocket must be clean and offer a firm location for the primer. The flash hole must be burr-free and have a consistent diameter. As for brand choice, I have my favourites and I suspect you’re the same? Mixing brands or types across a batch is a real no-no, as their performance characteristics vary considerably. However, if you’re developing a new load, be prepared to try different makes.
Lack of bullet consistency can undo all of your good works. Whilst all commercial brands and designs should offer safe and reliable performance, there are a number of important points to consider. Matching their true diameter to the neck diameter may sound a bit weird but some brands, especially those intended for military use, can be marginally under calibre. Weights can vary considerably, even from the top brands. Indeed, I cynically suspect that some makers add a runt to every box to reduce their scrap volumes! Batch weigh them, setting realistic tolerances. Remember that ogive damage can influence performance - which moves us to the tools.
The seating and fitting issues. An almost identical bullet from another maker is likely to have a slightly different ogive and give a significantly different fit in the seating punch. For that reason alone, don’t mix your bullets. On the subject of seating punches, don’t bodge or compromise. A poorly fitting punch or a build-up of crud will inevitably lead to either bullet damage or inconsistent seating depth or both. Replacements are only a tenner or so. If the cases are consistent and correctly sized, then neck tension should not be a problem. If the fit is inconsistent then check the bullet diameters. If we’re working with a cannelure, then the crimp can be yet another variable. Wherever you can, use a taper crimp, as they cause less damage and are more finely adjustable.
Talking of fine adjustments, the average die in the average press is a pretty poor example of it! Those of you with a Lee die set will be familiar with their locking rings. Inset into an annulus is a rubber O-ring. It is a clever means of ensuring that the die body has a degree of float, enabling it to self-align during the operation. A quick trip to your local engineering supplier will give you the same significant benefit. It does mean that for optimum accuracy you may have to reset the dies each time you start reloading a new batch, but the results are worth it.
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