Burstfire - Bullet Comparator & Headspace Gauge Set

Measure your brass against the standard — not against itself.

Most comparators give you a relative number: this case compared to that case, on your tool, on your bench. The Burstfire comparator set measures off the datum — the reference circle on the case shoulder that SAAMI uses to define headspace — so your number is anchored to the industry standard. Measure a case today, next season, or on a shooting partner's bench across the country, and you're speaking the same language.

Why datum-referenced beats relative

Bushings with chamfered or rounded measuring edges meet the shoulder somewhere along that chamfer — and "somewhere" shifts with shoulder angle, caliper pressure, and bushing-to-bushing variation. Fine for comparing two cases on the same tool; useless the moment you compare your number to a published dimension, a headspace gauge, or another shooter's reading.

Our bushings have a clean, sharp measuring edge cut exactly at the datum diameter. The shoulder contacts on one defined circle — the datum circle — every case, every time. That's the difference between a private number and a number that travels.

Pro tip: measure a certified headspace gauge once, note the small offset, and every reading after that ties directly to the standard.

Built like a measuring tool, not an accessory

• Screw-on stainless body. Bushings thread onto a 303 stainless steel body for a rigid, concentric fit — no wobble to corrupt your zero. Attaches to standard calipers (jaws up to 4.70 mm) with four brass grub screws.
• Machined to ±12 μm (about ±0.0005″), so the tool is never the weak link in the measurement.
• Type 2 hard-anodized bushings. 6061 aircraft-grade aluminum with a hard, ceramic-like anodized finish, color-coded by size — built for a lifetime of contact with brass without the measuring edges wearing soft.
• Headspace bushings made to their exact marked size, following SAAMI headspace gauge standards, each one individually pin-checked.
• Bullet bushings sized to bore rifling — the way the bullet actually meets the barrel, not a nominal number on a box.

What it does for your reloading

• Set your shoulder bump with intent. Dial in the 0.001–0.002″ bump precision bolt-gun shooters aim for (0.002–0.004″ for semi-autos) — no more over-sizing that stretches and work-hardens your brass.
• Verify the whole batch, not just the first case. Annealing creates consistency you can't see; a tight spread across twenty cases is how you prove it.
• Measure seating depth at the ogive, not the tip. Tips vary by as much as 0.025″; the ogive is what meets the rifling, so it's the measurement that controls your jump to the lands.

What's in the set

Complete Set — 20 pieces:

• 1 × screw-on stainless comparator body
• 5 × headspace bushings: .330 · .350 · .375 · .400 · .420
• 14 × bullet bushings: .17 · .20 · .22 · .24 · .25 · .26 · .27 · .28 · .30 · .33 · .35 · .37 · .41 · .45

Also available: Body + Bullet Set, Body + Headspace Set, body only, and individual bushings. The .450 headspace bushing (for .338 Lapua Magnum) is sold separately.

Choosing a headspace bushing: pick the one closest to the middle line of your cartridge's shoulder taper — that middle line is the datum the standard is built on.

Want the full story? Read our in-depth guide, Measuring What Matters: Datum, Shoulder Bump, and Seating Consistency — how datum measurement works, and how to set shoulder bump and seating depth with it.

Backed by the Burstfire lifetime warranty (wear excluded).