What bullet diameter is .243 Winchester Ackley Improved?

.243 Winchester Ackley Improved uses a 0.243″ (6.172 mm) diameter bullet.

Is .243 Winchester Ackley Improved still in production?

.243 Winchester Ackley Improved is active; typical availability is uncommon.

What is .243 Winchester Ackley Improved based on?

.243 Winchester Ackley Improved is derived from the .243 Winchester case.

Rifle · Proprietary

.243 Winchester Ackley Improved

.243 AI.243 Winchester AI

Ackley Improved version of the .243 Winchester; improved case geometry adds velocity for varmint and deer hunting with a proven cartridge..

Caliber: 0.243″ · 6.172 mm
Introduced: 1955
Case: Rimless
Parent: .243 Winchester
Status: Active

Velocity3,046–3,812 fps

Energy1,792–2,807 ft·lb · est.

Identity

Introduced: 1955
Type: Rifle
Origin: United States
Inventor: P.O. Ackley
Standard: Proprietary
Status: Active
Availability: Uncommon

Build

Primer: Boxer Large Rifle
Case type: Rimless

Pressure & range

Max pressure: 60,000 psi
Eff. range: 400 yd

Ballistics

Representative trajectory · 100 yd zero0–1000 yd

Open in Ballistic Compare ↗

Parent case: .243 Winchester

Representative trajectory — modeled from a single velocity input (no published BC for this cartridge yet).

Dimensionscase measurements · scale drawing · size vs familiar rounds

Case dimensions — the scale drawing at the top of the page is built from these.

CIP TDCC · approximate

Measure	mm	in	✓
Bullet ⌀	6.17	0.243	·
Neck ⌀	7.01	0.276	·
Shoulder ⌀	11.68	0.460	~
Shoulder angle	40°	—	·
Base ⌀	11.96	0.471	·
Rim ⌀	12.01	0.473	·
Belt ⌀	n/a
Rim thickness	1.37	0.054	·
Neck length	6.40	0.252	≈
Case length	51.94	2.045	·
Overall length	68.83	2.710	~

Size vs familiar rounds

Drawn at true 1:1 — every case is accurate relative to the others. Absolute size depends on your screen's pixel density, so measuring one against a real ruler may be off. .243 Winchester Ackley Improved is highlighted below.

Reloading costestimate cost per round vs factory

Estimate your cost per round and how it compares to factory. Inputs are yours — nothing is stored.

Powder $/lbCharge (gr)Bullet $/eaPrimer $/eaBrass reusesBrass $/ea

Cost estimate only — not load data. Charge weight is your input; follow published manuals for safe charges.

Lineage

Immediate parent

.243 Winchester

Family TreeOpen .243 Winchester Ackley Improved in the interactive cartridge family tree↗

Connected reference

FirearmsFirearms in .243 Winchester Ackley Improved↗ToolCompare ballistics↗

History

The .243 AI improves the already versatile .243 Winchester with a sharper 40° shoulder and more upright case walls, adding 50–100 fps depending on bullet weight. It is a popular choice for hunters and varmint shooters who are already set up for .243 and want to squeeze more performance from the case.

FAQs

What bullet diameter is .243 Winchester Ackley Improved?: .243 Winchester Ackley Improved uses a 0.243″ (6.172 mm) diameter bullet.
Is .243 Winchester Ackley Improved still in production?: .243 Winchester Ackley Improved is active; typical availability is uncommon.
What is .243 Winchester Ackley Improved based on?: .243 Winchester Ackley Improved is derived from the .243 Winchester case.

Sources & provenance

StandardSAAMI (Sporting Arms and Ammunition Manufacturers' Institute) — ANSI/SAAMI Z299.4 – 2015 (Centerfire Rifle) — Velocity & Pressure / Cartridge & Chamber Drawings · bullet ⌀archived
ReferenceP.O. Ackley (Plaza Publishing) — Handbook for Shooters & Reloaders, Vol. I — P.O. Ackley · velocity, bullet ⌀

Data & sources. Specs compiled from the Lindcott Armory reference; the trajectory is modeled (point-mass), not measured. See methodology. Spotted an error? Report it →