Target Sports

SPECIAL FEATURE: MADE TO MEASURE

Created on 14th May 2009

LAURIE HOLLAND takes a look at common types of measures, the factors affecting consistency, and compares features and prices on some of the best

AN ANOMALY that puzzles many tyro handloaders is the apparent contradiction between advice that smokeless powder charges are measured by weight, and the fact that every handloading tool manufacturer offers powder measures that work through volume. However, the purpose of these tools is to produce a near identical volume on each throw, the practitioner weighing the result and adjusting the tool to get the exact charge weight required.
What are we looking for? An ideal measure will:

• produce identical charges each time

• be easily adjusted through a metering/setting system with graduations that allow return to previous settings

• throw a wide range of charge sizes reliably

• provide consistent results as the powder level in the reservoir reduces

• handle all types of powder reliably and smoothly from fine ball types to coarse extruded sticks without jamming the mechanism, or ‘bridging' (sticking) in the drop tube

• have a large capacity reservoir

• be suitable for automatic operation on turret/progressive presses if required

• have a drain facility to empty after use (for progressive press use)

• be as cheap as chips, and last forever
Of course, we won't get all of these things, as some demands are conflicting.

Ways and means

Most measures are built around a measuring chamber whose internal volume, hence the size/weight of charge thrown, is user-adjustable. A commonly seen type is a ‘pencil' or cylinder with its open end located within the measure's cylinder/rotor, a metering piston screwed in or out. A few use a sliding bar system in which a block or bar is moved horizontally by the adjuster mechanism. This applies to expensive ‘Culver system' measures, the main benefit being not any vast improvement in metering consistency but more the accuracy of the adjustment mechanism, which allows very small changes to be made in the size of charge thrown. (It also provides a high degree of ‘repeatability' in that a particular setting will throw precisely the same volume of powder every time, subject to powder lot density.) A third, less common method is the oldest and simplest - the fixed volume measure. The charge cup is its cheapest and simplest manifestation and a modern version is available from Lee Precision. Lee also uses interchangeable plastic disks which incorporate fixed cavities in its ‘Auto-Disk' measure. At one time several manufacturers produced rotary-type measures that used interchangeable cylinders with a fixed metering chamber factory-machined in, mostly used for pistol cartridge charges. The user would buy rotor(s) for the charge(s) looking up a table to see what volume chamber was needed for the powder plus charge weight. To my surprise the RCBS ‘Little Dandy' is still in production with 26 different rotors available, although the UK RCBS distributor doesn't list it.

Black powder

Ordinary measures should never be used for this propellant as they use plastic and/or ferrous metal parts that risk ignition caused by static electricity or friction-sparking. Some manufacturers list specialised black powder measures.

Consistency

No mechanical measure throws absolutely consistent charges - even the expensive benchrest ‘Culver' types produce 30gn ±0.1gn on 30gn charges. Factors affecting this include:

• Metering chamber size and design. (Note Hornady and Redding BR measures use inserts with concave piston heads and are also smaller diameter than on standard models.)

• Fit and finish of the moving parts to provide smooth operation and avoid gaps that can cause powder grains to be trapped or cut by the measure as it operates. Hence roller-bearings in the Harrell's Precision measures, hand-honed cylinders/bodies in the Redding BR series, and the plated Hornady BR rotor. Allied to design/manufacture factors is operator technique - experiment to see what works well then do it consistently. Finally, powder type - some sizes/shapes of extruded powder make even the best measure operate jerkily.

• Sophisticated micrometer metering units - this may not provide increased consistency in itself, but allows small changes and previous settings to be replicated. I know that my Harrell's Precision Premium BR measure set at 81.0 will throw exactly 44.0gn of my current lot of Viht N150. Even so, actual charges are check-weighed at the start of the loading session for safety.

• The size of the measure and range of charges it throws. A big measure that can throw a 10gn charge of 2400 at one end of its setting and 90gn of H1000 or Reloder 25 at the other can't be expected to produce absolutely consistent 30gn charges of Viht N130 or H322 for the precision shooter - that's why precision measures come in various sizes and those used by PPC/BR shooters are designed around this charge weight.

• The amount of powder in the reservoir hopper. If you start with a pound of powder and don't replenish it during the session, charges will likely reduce as there is less pressure from above forcing powder kernels into the metering chamber. A baffle in the reservoir helps.

• Mounting robustness - if the measure waves around like a silver birch in the wind it won't throw consistent charges. You need a rigid stand mounted on something solid.

A note on prices

Prices quoted are at 2008 levels. With the pound having lost 25% of its value against the US dollar in recent months, importers say that there may be large price rises as new shipments are received. Add 20-25% to the quoted pound sterling prices to get an idea of those likely to apply.