The Australian International Arms project started in 1997, to manufacture and market a large-capacity, bolt action rifle. Concept: to produce a new generation body with magazine adaptors for different cartridge lengths, incorporating the Brewer collar and barrel system and an interchangeable bolthead. The three cartridges chosen were: 7.62x39mm, 7.62x51mm and 5.56x45mm.

For the type of action and practicality of production, AIA decided upon the Lee, the most developed with a century in service, manufactured and improved by the world’s leading factories on three continents.

The No.4 Mk 2 was chosen as the most practical, given serviceability and accuracy of the 7.62mm L39A1 and Envoy. The first AIA prototype was assembled in 1998 using a No.4 body mock-up, serial numbered XP00001. As a body only, with proposed magazine adaptors and interchangeable barrel and bolt-head, the initial action was not in a specific calibre. This new series was initially designated ‘No.4 Mk 10’; this nominated as the ‘Type 00’ action body.

In 1999, the next prototypes were new-manufacture bodies with the 7.62x 39mm adaptor. These bodies had the bolt-head release catch behind the charger bridge like the original No.4 Mk I & Mk 2. This was then altered to the Savage and Long Branch Mk I* style with bolt-head release slot at the front, near the chamber.

It is interesting that development advanced in parallel with the British and North American Lee-Enfields, allbeit at a faster pace! After extensive testing and evolution through a number of body types designated as Type 01, Type 02, &c, the end result for the M10 is a Lee-Enfield of the 21st century, the new millennium. Fifth generation Lee-Enfield, in essence ‘re-inventing the wheel.’

Over 60 years and millions of pounds in Lee-Enfield development, most improvements had already been incorporated in the British, Canadian, US and Australian manufacture. However, in a comparable search for the ‘ultimate’ bolt action, the new M10 has the advantage of contemporary CNC milling, forged steel receivers, full-floating barrel, stronger charger bridge to stiffen the action body, and a contemporary magazine case.

AIA’s original concept was to use some surplus parts but it was found that most of these ‘new’ parts were prior factory rejects. The Model 10 is made completely from new parts, using high grade steel and teak timber; no plastic, nylon or alloy. The result is a heavier rifle, but as competition shooters and marksmen attest, these shoot so much better.

The CIA/Woolwich hung trigger, Stevens-Savage bolt head release, early hinged outer bands, two-stage trigger, Lithgow cocking piece, dual L-aperture (Singer Mk I range adjustable leaf will fit), Long Branch safety catch and L42A1 sniper bedding plate on 7.62x 51mm models; all incorporated in AIA’s ‘new’ M10.

AIA’s development of body types is generally evident by serial nos. Receiver types are denoted by the first two numerals of the numeric part of the serial number. See Chapter 16 of the new 'Lee-Enfield' book for a Serial Number breakdown.

00 Toolroom prototype bodies made in concept development from 1997 to 2000. The initial bodies made by ‘cut & paste’ of No.4 Mk 2 receivers. Later bodies were milled from the solid to conclude with the Type 01 receiver.

01: Toolroom eXPerimental production bodies of initial 7.62x 39mm No.4 Mk 10 trials batch. 50 made, 25 used as initial market evaluation samples in Australia, 17 used in function trials and component destruction testing, 8 used to build 2002 Shot Show display samples. Nomenclature abbreviated to M10 following market research. Major type change from Type 00 was the bolthead release mechanism.

02: Action body designed for 7.62x 39mm Major change from Type 01 body was extending receiver reinforce rearward to behind the bolt locking lug recess. Mass production from forging. Majority of production was sold in Australia with limited numbers supplied to USA, EEC and Canada.

03: Body originally designed as universal receiver for all calibres. About 90 made before receiver and magazine adaptor design was simplified to make only 7.62x 51mm. Some units sold commercially in Australia except for samples to other markets. Majority of units held for testing and reference.

04: Body specific to 7.62x 51mm volume production. Current for No.4 Mk 4 and M10-B1 with transition from welded bridge piece to solid bridge.
Four sub-variants:
WW: Welded bridge cross piece with Whitworth-form barrel thread.
SW: Solid bridge cross-piece with Whitworth-form barrel thread.
WU: Welded bridge piece with UNEF-form barrel thread.
SU: Solid bridge piece with UNEF-form barrel thread. This form remains in continuing production. All export units are this sub-variant.

05A: First production of solid bridge body with radiusing of edges, sporting look. Bridge made solid extending past rear action body machining for Mk I Singer rearsight. Also designated T05 Long Bridge. Supplied only to Australia.

05B: Second production of solid bridge receiver with radiused edges. Bridge solid only to rear body machining for Singer rearsight. Designated T05 Short Bridge. Supply to Australia & Canada.

06: Same as Type 05A except for reduced diameter UNEF barrel for fitting of M134-design barrels. Locking collar changed accordingly. In all other production, the receiver's barrel thread diameter is per current Savage manufacture, but to finer gauging tolerances.

07A: Type 06 body re-designed for use in one-piece stock furniture. Lightening cuts and machining for emulation of J-5550 Canadian Light Rifle to be determined. Design of trigger system and consequent body modifications being finalized. Special lightweight profile barrel to be fitted.