Guide
Squib Loads: What Causes Them and How to Prevent Them on a Progressive Press
A squib load is a round with too little powder — or none at all — behind the bullet. Fire one and the primer (plus whatever powder is present) usually has just enough energy to push the bullet partway down the barrel, where it stops. The danger isn't the squib itself; it's the next trigger pull. Fire a full-power round into an obstructed barrel and you can bulge or burst it, wreck the gun, and injure yourself or the shooter next to you. Squibs and their evil twin, the double charge, are the two failures every powder-checking system exists to prevent.
Why progressive presses produce squibs
On a single-stage press you charge a block of cases and look into every one. A progressive does five to ten operations at once, hundreds of times an hour, and the powder drop happens out of your line of sight. The classic causes: an interrupted rhythm (you clear a primer problem, then cycle the press without a case getting charged), powder bridging in the measure or hopper (fine and flake powders are notorious for hanging up, dropping light, then dumping the difference into the next case), a hopper running dry mid-session, static cling in dry climates, and a case that tipped or was missing entirely so the charge went nowhere. Every one of these produces a case that looks normal from above the shell plate.
Small pistol charges make it worse. A 9mm case designed for up to around 33,000 PSI runs happily on ~3–4 grains of fast powder — which means the case is mostly empty space. An undercharge is visually almost indistinguishable from a correct charge at a glance, and a double charge still fits without overflowing. The eyeball test that works for a case-filling rifle load fails exactly where most high-volume loading happens.
Warning signs when shooting
Know these cold, and teach them to anyone who shoots your reloads: a noticeably quieter report (often a "pop" instead of a bang), reduced or absent recoil, the action failing to cycle on a semi-auto, or anything that feels different from the last round. The response is always the same — stop immediately, unload, and check the bore from the breech end with the gun pointed safely. If there's a bullet in the barrel, it comes out with a squib rod and patience, not with another round. If you even suspect a squib mid-match or mid-drill, the string is over until the bore is verified clear.
Prevention, layer by layer
Layer one is process: never cycle the press to "catch up" after clearing a problem without walking the shell plate backward through what happened; keep the hopper visibly topped up; settle on one powder-handling routine and never improvise mid-session; and keep distractions (phone, TV, conversation) away from a running press.
Layer two is verification you can see: adequate lighting over the shell plate and a deliberate look into the case at the station after the powder drop, every cycle, if you load manually. This is free and it works — right up to the speed where it doesn't. Attention is a consumable; at high volume it runs out before the brass does.
Layer three is instrumentation: a powder check that measures every case and acts on what it finds. The options range from watch-it-yourself indicator dies to alarm systems to laser measurement with automatic press stop — we compared all of them honestly in this guide. The short version: as volume and automation rise, you want the check to be non-contact (no spills or probe issues), automatic (stops the press rather than hoping you hear a beep), and tight enough to catch partial undercharges, not just empty cases. That's precisely the job laser powder checks were built for — and a case presence sensor closes the loop on the missing-case and tipped-case failures that powder checks alone can't see.
Layer four is data: logging every round's reading turns "I think that session was clean" into a timestamped record. When something does trip the alarm, the charge history shows whether it was a one-off bridge or a powder measure drifting for the last 200 rounds. For commercial loaders, that CSV trail is the difference between asserting your QC and proving it.
The takeaway
Squibs aren't caused by carelessness so much as by trusting attention to do a machine's job at machine speeds. Build the layers: disciplined process, eyes where they matter, instrumentation that never blinks, and a data trail. If you want help spec'ing a check setup for your press — Mark 7, Dillon, or stand-alone — talk to us; we load on these machines every week.
Keep reading
Powder Check Systems Compared: Powder Cop vs. Lock-Out Die vs. Dillon vs. Laser · RCM Laser Powder Check vs. Mark 7 PowderCheck Sensor: An Honest Comparison · Mark 7 PowderCheck False Alarms: Causes, Fixes, and When to Upgrade · Double Charges in 9mm: Why They Happen on Progressives and How to Catch Them