How to Evaluate an Ammunition Weighing System
Buying an ammunition weighing system is not the same as buying a scale. A lab balance tells you what one part weighs. An inline weighing system has to decide, thousands of times an hour and without anyone watching, whether each round is good enough to ship. That decision rests on four things: how repeatable the reading is, which load cell is doing the weighing, how fast the machine can go without losing either, and what it does when a reading can't be trusted.
This guide walks through the questions a QC manager, plant engineer or government buyer should ask of any ammunition weight sorting system, and shows how we answer them for the AccuWeigh 360. Every figure for our equipment below is taken from the published specifications. Where a number depends on your line, we say so.
Start with what weight can and cannot tell you
Weight is a proxy. A finished cartridge is the sum of its case, primer, powder charge and projectile, so a round that is missing a component or carries the wrong amount of one usually shows up as a weight outside the normal band. Our product page lists what weight inspection is built to catch: "a missing primer, a light or heavy powder charge, a wrong or defective projectile, damaged brass."
Weight cannot see shape. A round can be the right weight with a crushed shoulder, a split neck or an over-length overall dimension. That is why we pair weighing with optical inspection on the AccuVision 360, which measures dimensions the way a case gauge would and runs at 6,000 to 10,000 rounds per hour, by caliber and configuration. Weight also cannot catch every ignition problem, a limit we covered in our post on squib load detection.
So the first evaluation question is not "how accurate is it?" It is "which defects am I asking this machine to catch, and how small is the weight difference each one creates?" Once you know the smallest difference that matters on each product, you can judge whether a system's repeatability is good enough to resolve it.
Grain-level repeatability: the number that decides pass or fail
Vendors often quote "accuracy" or "resolution." Resolution is just the smallest step the display shows. What matters for sorting is repeatability: if you weigh the same round over and over, how much do the readings scatter?
Ask three things about any repeatability figure:
- At what confidence? A figure stated at one standard deviation describes the typical scatter. Your limits should sit well outside that band so a good round is not rejected on noise and a bad round is not passed on luck.
- On which load cell? Repeatability gets coarser as cell capacity goes up. A single headline number with no cell attached tells you very little.
- Under what conditions? Inline weighing happens on a moving line, next to loaders and feeders. Ask whether the figure applies to the machine running at its rated speed.
For the AccuWeigh 360, the published repeatability is "0.1 grain at one standard deviation on the 10 gram cell; 0.2 grain on the 30 gram cell; 0.6 grain on the 80 gram (1,234 grain) cell." Limits can be set "as tight as 0.1 grain or as wide as ten grains for large rounds."
A practical way to use that: list the smallest defect you need to catch on each product, in grains, and compare it to the repeatability of the cell that product would run on. If the defect is several times larger than the scatter, weight will separate it cleanly. If the two are close, tighten the process upstream, add another inspection method, or both.
Load cells: match the cell to the part
The load cell is the sensor that turns weight into a signal, and its capacity sets both the heaviest part it can weigh and the fineness of the reading. A buyer should ask:
- What cell sizes are offered, and what is the repeatability on each?
- Which of my products fall on which cell? Light pistol components and heavy rifle rounds may not belong on the same cell.
- Can cells be added or swapped later?
On the AccuWeigh 360 there are three: the 10 gram, 30 gram and 80 gram cells listed above. As a rough guide, 10 grams is about 154 grains, so only parts lighter than that, such as many projectiles and pistol cases, can run on the 10 gram cell, where the scatter is smallest. Standard configurations cover "cases, projectiles and loaded rounds, .308 to 9mm," with larger calibers quoted. Size limits matter too: projectiles must be "at least 0.5 inch long and 0.25 inch in diameter," and loaded rounds can be "up to 2.25 inches long and 0.5 inch in diameter."
If a vendor can't tell you which cell your product runs on and what repeatability that cell delivers, you don't yet have the information to judge the machine.
Throughput: ask how the rate is built
Every weighing system trades speed against settling time. A part has to land, the reading has to stabilize, and the machine has to decide before the next part arrives. When you compare throughput figures, ask how the rate is reached, not just what the top number is.
The AccuWeigh 360 is modular. It starts at 3,600 parts per hour with a single weigh cell, which is 28,800 in an eight-hour shift, and scales past 12,000 parts per hour as weigh cells are added. The rate grows by adding weigh cells. That is the point to press with any vendor: does a higher rate come from more weighing stations, or from less time per reading?
Size the system from your own numbers:
- Parts per shift at the inspection step. Take your loader output, not the rated speed of the loader.
- Headroom. Inspection should never be the bottleneck. If the weigher can't keep up, operators will be tempted to bypass it.
- Feed. A weigher is only as fast as the parts reaching it. The AccuWeigh 360 is fed by an AccuFeed collator or a Dillon-style case feeder, and a live-round feed kit is quoted per job.
Tell us your calibers and volume per shift and we will quote the cell count your line needs.
Decision logic: what happens on a bad reading
This is the question many buyers skip, and it is the one that matters most for liability. Every sensor sometimes produces a reading it shouldn't trust: a part bounces, two parts touch, vibration spikes. What does the machine do then?
A system that defaults to "pass" when it is unsure will, sooner or later, ship a bad round. Ask any vendor directly how marginal and unreadable parts are handled.
Our answer is on the technology page: "The logic fails safe: when a reading cannot be trusted, the part is rejected rather than assumed good." The patent-pending firewall logic means "a defective cartridge or component can never be passed as good." The weight inspection platform is designed to twelve sigma, which we define as "roughly one component or round weighing a tenth of a grain outside its limit and still passing in twelve billion." Treat that as a design target and ask any vendor for theirs in the same terms.
Data: can you prove what the machine did?
For contract and defense work, an inspection step only counts if you can show it happened. When evaluating a system, ask:
- Is every part's weight recorded, or only rejects?
- How long is the record kept, and can it be pulled by lot?
- Can the data feed a central quality system?
The AccuWeigh 360 stores "up to 25,000 preset configurations and a record of every part weighed," with "Six Sigma compatible data output; optional remote data feed to a central system." Weight data can be reviewed by lot number or by individual round. That record is what turns a weighing step into evidence during an audit or a customer complaint, and it supports the case for 100% weight inspection over sampling.
Sorting, not just rejecting
Pass and fail is the minimum. Some buyers also want to sort by weight class: brass and projectiles into tight groups for match loading, or finished rounds by total weight for boxing. Ask how many outputs a system supports and whether it can grow.
The AccuWeigh 360 ships with two outputs, pass and fail, as standard and supports "unlimited bins for weight sorting." Combined with headstamp sorting on an AccuSort, that is how standard components become match-consistent ammunition.
Day-to-day operation
The best specification is wasted if operators work around the machine. Ask about:
- Changeover. How long does it take to switch calibers or limits? Stored presets make this a selection, not a setup.
- Access control. Who can change a limit? The AccuWeigh 360 has user access levels and a one-touch interface, plus a manual weigh mode that needs no setup.
- Install and support. We quote delivery at four to six weeks from order on every system. Setup takes about four hours, including remote training, and nothing needs an internet connection to run. Each system includes a one-year parts warranty and free software updates.
A short checklist for your evaluation
- Repeatability stated per load cell, at a stated confidence level
- Your smallest critical defect, in grains, compared with that repeatability
- Throughput per weighing station and how it scales
- Feed method and its real rate on your calibers
- Fail-safe handling of marginal or unreadable readings
- A record of every part, retrievable by lot
- Sorting outputs beyond pass and fail
- Changeover time, access control, setup and support terms
Talk to us about your line
If you are comparing ammunition weight sorting systems, send us your calibers, components and volume per shift. We will tell you which cell your product belongs on, what repeatability to expect, and how many cells your line needs. Contact Ammo Inspector to request a quote.