May 9, 2026 · By Diane Johnson
New to these numbers? Start with our guide to SD vs ES. This one is about using them across a season.
In a PRS match nobody gives you a known distance and a sighter. You get a stage brief, a par time, and a target you've never ranged sitting somewhere past 600. You build your dope from a chronograph reading you took weeks ago and trust that the load will hold. When it doesn't, you don't miss by a hair. You miss high or low, off the plate entirely, and that stage is gone.
Single-digit SD isn't a number you post to brag. It's the difference between a center hit and a splash in the dirt when the call is right and the load is the only thing left to blame.
At distance, drop gets steep and unforgiving. A round that leaves 20 fps faster than your average impacts high; one that leaves slow drops below the plate. That vertical scatter is exactly the error that decides PRS stages, because the targets that matter are far and you can't see your trace well enough to correct mid-string under a clock. Standard deviation describes how tightly the whole string holds to its mean, so it's the number that predicts how much vertical you'll eat on an unknown-distance target. Extreme spread is just your fastest shot minus your slowest, so it tells you how ugly your worst pairing got. You want the first one small to win consistently and the second one small so a single flier doesn't cost you a stage. Read both, but trust SD.
Here's where match shooters get burned. You work up a load in October, see a 7 fps SD over ten rounds, and write that down as gospel. Then the season runs and the rifle changes underneath you. A new lot of powder meters a hair different. A 40-degree morning burns slower than the 90-degree afternoon you developed in. Two thousand rounds of barrel wear move your node. None of that shows up if your only data point is one good string from one good day.
So track SD and ES across charges and across the calendar. Every chrono session goes in the same record next to the last one. Over a season you stop looking at a single string and start looking at a trend line. That's the view that tells the truth.
Use the running data to choose. The match load isn't the charge that printed the single lowest ES on its best day. It's the charge whose SD stays low across multiple sessions and conditions, because that's the one that holds together when you can't reshoot. A node that's stable over fifty logged rounds beats a node that looked perfect over five.
Then keep watching. When your mean velocity starts creeping or your SD opens up two matches in a row, that's drift, and now you've caught it on the data instead of on the scoreboard. A barrel that's walking up in velocity needs a dope correction before the next match, not an explanation after it.
Velocity has a temperature dependence, and a match doesn't always start warm. Note the conditions with the string. Over a season that lets you separate cold-bore behavior from a fouled, heat-soaked barrel late in the day, and it tells you how your particular powder shifts when the morning is cold. That's the knowledge that keeps your first-round impact on a hard, far target instead of guessing.
LoadOut logs each shot straight from your chronograph — a Garmin Xero over Bluetooth, for instance — and computes mean velocity, SD, and ES per charge weight. Every session stacks onto the last, so you're holding a season's worth of strings for each load rather than a screenshot you took once and lost. You can see which charge held its SD across the calendar, where a flier inflated an ES, and the moment a node starts to walk. It's local-first, so that whole record lives on your device, not on someone's server. This is general guidance, not load data.
A match load is a moving target. LoadOut keeps the data that tells you when it drifts. Explore LoadOut →