Methodology

Last updated: April 16, 2026

This page is the technical backing for what you see on every caliber, prices, and ballistics page. If you want to know exactly how a number was computed, it's described here.

Cost per round (CPR)

CPR is the single most important number on this site. It is defined as:

CPR = listing_price / rounds_in_box

When a retailer lists a case (e.g., 500 rounds), we use the case price and case count. When a retailer lists a "bulk" pack that isn't a standard box, we still divide total price by total rounds — CPR normalizes all pack sizes to a single comparable number.

CPR is stored in cents (cpr_cents) so arithmetic is integer-safe. Displayed values are rounded to the nearest cent.

CPR color tiers

The colored badges on listing tables are relative to the caliber's current market:

• Green ("Great deal"): listing CPR is ≤ 90% of the average CPR for that caliber.
• Amber ("Fair"): listing CPR is between 90% and 105% of the average.
• Red ("Above average"): listing CPR is > 105% of the average.

The average is the mean CPR of all in-stock listings for that caliber at the time of page build.

Price history & trend

We snapshot every tracked listing daily and keep 90 days of history. The price history chart on each /prices/[caliber] page shows the average CPR across all in-stock listings for that caliber, per day. Individual retailer lines are available on the detail listing page.

The trend arrow on caliber summaries compares two windows:

• Average CPR over the last 7 days
• Average CPR over the 7 days before that

A difference greater than ±1.5% triggers the up/down arrow. Smaller differences display as flat. This threshold filters out normal day-to-day feed noise.

Ballistics

Ballistics data comes from manufacturer-published factory-load specs. Each cartridge has one representative load documented at standard distances:

• Velocity (fps) at 0, 100, 200, 300, and 500 yards
• Energy (ft-lbs) at the same distances
• Drop (inches) at 100, 200, 300, and 500 yards

The load source (for example, "Federal XM193" or "Hornady Match") is stored with each row and surfaced on the ballistics page.

Barrel-length velocity estimate

Real velocity depends on your specific firearm. Our ballistics tool estimates the effect of barrel length using a standard approximation relative to the manufacturer's reference barrel (typically 20" for rifles):

• Rifle cartridges: ~25 fps per inch of difference
• Handgun cartridges: ~15 fps per inch
• Rimfire: ~8 fps per inch

This is a rough comparison tool, not a replacement for chronographing your own setup.

Retailer coverage

We track listings from the retailers named on our affiliate policypage. When a retailer feed drops a product, its listings disappear from our tables on the next build — we don't leave stale listings up.

Build cadence

• Price pages revalidate every 15 minutes on request.
• Caliber overview and ballistics pages revalidate every hour.
• Static pages (homepage, brands index, trust pages) rebuild on deploy and daily.

Questions or corrections

Methodology questions, data disputes, or bug reports: editorial@precisionammo.com.