Handloading Part X
- By Wheelwrite
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- Last updated: 15/12/2016
When it comes to handloading; accuracy and consistency is all! Exact measurement of not only the propellants but the projectiles, firearms and cartridge cases are key factors in achieving quality ammunition. We therefore need to be tooled up to measure not only weight but physical size. With scales we require an operating range that will span everything from the heaviest bullet to the smallest powder charge.
In reality that means weights from half of 1/10th-grain (approx. 1/154,000th of a kg!) up to 400 to 500-grains. Throwing (dispensing) powder charges also involves the use of a volumetric device – the powder measure. Checking cases, firearm and bullet dimensions requires verniers and micrometres that measure down to at least 0.025 of a millimetre. It does not stop there… we also have access to ‘speed’ measurement devices, known as comparators. These are often designed in the form of a ‘go’/‘no-go’ gauge allowing swift comparison between the subject, such as the length of a cartridge case or the size of a chamber, and a fixed dimensional standard. Other ‘fixed’ measures include the Lee powder scoop system. Finally, we need to check the checkers… especially our scales. Dedicated check weights are the ideal solution.
Scales of Weighing
Most mechanical handloading scales use the balance beam method in a comparative mode. You set a desired weight at one end and it compares it to what you place on the other, with a fulcrum point between these two to allow it to swing and then balance. Ideally they have a three part measurement system, divided into 10, 1 and 1/10th grains (1/7000th of a pound). On the other end is a support tray that holds a removable receptacle (the pan). For optimum performance they have to be used on a firm flat surface in a location free from vibration or draughts. With each of the three segments set to zero and the pan in place you have to zero it. This is achieved by turning a threaded foot at one end that raises or lowers the body in relation to the pointer at the end of the beam. When the pointer is at rest and aligned with the zero mark the scale is ready for use.
If the packaging of the new scale has been damaged, or the scale is visibly worn then it is essential that the quality of calibration is checked. Companies such as Lyman offer check weights that can be used to check its overall accuracy. A scale that has a measurable degree of error should be binned. When not in use they should be covered and kept safe. Over time, especially if used for weighing heavier objects like bullets and cases, the discrimination will reduce. This happens because the fulcrum points of contact become worn. This justifies the regular use of check weights. If funds permit, using two separate scales - one for powder, (a Competition set), and another for components is no bad idea.
Electronic scales give an actual readout – essential for benchrest and other high accuracy endeavours that demand the batch weighing of bullets and cases. Whilst the scale may be powered by electricity it still has a mechanical device at its heart and for that reason should be kept secure from risk of damage and periodically checked for calibration. If a battery change does not resolve irregular or inconsistent readings then the device must be binned.
Thous, Mils and Microns
Every serious hand loader will need at least one linear measuring instrument for checking bullet diameters, case dimensions and even overall cartridge length (COL) - there are plenty of applications for such a tool. The simplest is a mechanical, vernier caliper calibrated in 1/1000” (thous). It permits both inside and outside measurement over a wide range of sizes but can be easily misused due to the absence of any pressure control on the jaws. Never rely on a plastic version – they’re not much better than toys. If reading the scale is a problem, or you need to measure in both Imperial and metric units then an electronic (digital display) vernier may be the best choice. For the most precise measurement of items such as bullets, especially swaged soft lead, a quality micrometre is essential as it will have flat anvils (measuring faces) and a clutch drive for the jaws. Keep instruments secure when not in use – I’ve heard tales of kids using a vernier as an adjustable spanner… The pros and cons of electronic versus mechanical are well balanced for these instruments – the vulnerability of battery power offset by the ability to electronically re-zero and to switch from one unit to another.
How Big is 25 Grains of Propellant?
No, that’s not as daft a question as it may seem. For convenience a lot of reloaders use a powder thrower, which consist of an adjustable charge bar and a hopper that holds the propellant. Once set all you do is cycle the bar to throw a pre-set charge weight. However, I would caution you; this is about volume and not weight as a scale offers. The type of propellant (size/shape of the individual power kernels) will fill up space in a different way, so despite most charge bars being graduated you must weigh what is thrown to check you have it right. Then repeat/adjust a few times as the powder density will change due to operating vibrations.
Volume is the basis for the Lee scoop system too. Here you simply pass the scoop through the powder and fill it level to the brim. Lee supply a chart that gives capacity to weight information and it’s surprisingly effective. However, actual charge weights MUST be checked on a scale to see what you are getting.
Comparators come in a multitude of forms. The simplest is the Lyman device for checking standard case lengths for the most popular calibres, simply slide the case into the jaws. Sets of double ended plugs are available to establish the go or no-go sizes of chambers. And on to a topic that takes us to headspace, SAAMI and CIP… the likely subject of another monthly rant!
1, Typical, 3-weight (10s, 1s & 1/10th ) balance beam scale, this is from Hornady and will allow you to weigh from 500 down to 1/10th – grain and you will need this precision to make decent reloads too
2 & 2a, A decent, metal vernier calliper allows the checking most critical measurements such as COL etc., here we see a clock gauge-type and another with a digital readout
3, RCBS UniFlow powder dispenser, this is a volumetric device and not one set up to throw by weight, which must be checked on a scale prior to case filling
4, An alternative to the balance beam scale is the electric, which is generally easier to set up and use with no loss of accuracy either
5, This micrometre will allow you to measure case neck wall thickness, a little specialised compared to the normal type, but in a job where precision and consistency is all; very useful
6, Scales will wear so a set of check weights is a valid consideration
7, This tool will allow you to check COL adjustment to get the perfect bullet seating length for your load/rifle
8, Simple but effective – the Lyman cartridge case gauge