Lee-Enfield M4A1 Carbine review with Mike Morton

Mike Morton goes into action with the CO2-powered, BB-blasting, US military-themed M4A1 Carbine from Lee-Enfield Guns.

While some CO2 guns are totally original designs, others are inspired by powder-burning firearms, with the Brothers In Arms series of historical replicas from Lee-Enfield (Guns) falling firmly into the latter category.

The M4A1 was developed by Colt and is in service with multiple operators around the world, notably the US Army, with the Marine Corps due to follow suit. 

But while that gun fires 5.56x45mm NATO rounds, this CO2 variant shoots 4.5mm BBs. It features all-metal construction throughout the barrel, receiver and the 18-round magazine. 

Plenty of plastic has been used here as well, most notably the handguard, pistol grip and telescoping butt stock, but that’s the case with the original M4A1 too.

The 5.56mm M4A1 was accepted into service by the US military in 1994. It first saw action in the hands of US troops deployed to Kosovo in 1999 in support of NATO forces, and has been used in several conflicts across the globe since. 

Lee-Enfield’s Brothers in Arms series focuses on iconic weapons from the 20th century, so the M4A1 here is one of the earlier Kosovo-era versions, the most obvious features being the rounded two-piece handguard and the removable carrying handle/rear sight assembly.

Lee-Enfield M4A1 Carbine – key specifications

Distributor: The Shooting Party (shootingparty.uk)
Manufacturer: Lee-Enfield (Guns)
Sub-series: Brothers In Arms
Model: M4A1 Carbine
Price: £159.99
Powerplant: Single CO2 capsule
Action: Blowback
Calibre: 4.5mm (steel BBs)
Magazine capacity: 18 BBs
Trigger: Single-action
Safety catch: Manual
Sights: Open, adjustable
Stock: Length-adjustable
Overall length: 760mm-830mm
Barrel length: 372mm
Weight: 3.2kg

Real Versus Replica

One of the highlights of this gun – as with any modern M4/AR-15 platform – is the telescoping butt stock. Carbines are shorter than a standard rifle, which is a desirable feature for close-quarters or mechanised use, but still offer much of the range and power of a regular rifle. 

Regardless of the M4A1’s overall length, the telescoping butt stock means it can be adjusted to suit your own physical build by depressing a lever, enhancing gun fit. 

And when you’ve finished shooting, the stock can be fully collapsed so that it takes up less space during transit or for storage. 

Being of average height, but with the arms of an orangutan, I took advantage of extending the butt stock to its fullest position.

The M16, from which the M4 Carbine was derived, had a fixed carrying handle, but with the M4A1 soldiers were given the option of removing the handle so they could use the Picatinny rail underneath, and that’s what you get with the Brothers In Arms gun too. 

The Carbine comes with flip-up open sights, with the rear sight being integrated into the handle. And if you want to fit an optic, all you need to do is remove the handle/rear sight assembly to expose the 5.5” rail. 

I kitted out the gun both ways, but ended up spending most of my time shooting it with the standard iron sights as I felt this was more in keeping with the 1990s ethos of the particular model it’s based on. 

The handle also incorporates thumbwheel-style elevation and windage controls, which thankfully work as intended.

While the safety catch has been faithfully reproduced, there’s no functioning “Auto” mode on the Brothers In Arms version, just the blowback option

Civilian AR-15s are totally customisable, and while M4s can be modified too, most soldiers just end up with what they’re given, and that means a butt stock that offers no height adjustment of the butt plate or cheekpiece. 

This feature, or rather lack of it, has understandably been reproduced here, but it wasn’t too much of a disadvantage. I’m of fairly standard build, and found the sight picture to be pretty good despite the fixed height of the cheekpiece.

Rather than just creating a functioning BB gun that happens to look like an M4A1, Brothers In Arms has gone the extra mile to create a more convincing replica by incorporating semi-workable features that play no actual functioning role on the airgun. 

Take the forward assist, for example. This control, which sticks out the rear right-hand-side of the action and looks like the choke on an old car, is designed to push the bolt carrier fully forward, seating it correctly in the event of something like a misfeed of a 5.56 round. 

I’m assuming it would have been easier and cheaper for Brothers In Arms to have produced the forward assist on the replica as a single non-functioning part, but you can press the button forwards under spring tension. It doesn’t do anything, but mimics the original nicely.

Then there’s the two-part handguard. This is spring-fitted and can be removed by pulling down on the collar at the base of the barrel, after which the upper and lower sections can be taken off. 

This in itself is another nice feature, which once again plays no role in the actual function of the airgun, but better yet is the fact that removing the handguard reveals a copy of the gas piston system that made the M16/AR-15/M4 family of rifles so successful. 

It’s another feature that needn’t have been included, but it’s good to have in terms of the accuracy of the replica – and as a tool to illustrate the features of the real M4.

Ready For The Range

The heart of the Brothers In Arms M4A1 is the magazine, which displays some clever engineering. 

The 5.56mm box mag is a shell which holds a BB magazine and CO2 unit. This internal magazine is held in place with a sprung plunger, which can be depressed with your finger, and can then be extracted and loaded with up to 18 rounds. 

The follower can thankfully be locked open inside a gate while you load the ammo, a feature I’d love to see on all BB magazines of this type. The CO2 capsule is pierced by turning in the retaining screw at the bottom of the mag with the supplied hex key, remembering not to overtighten it.

As with the 5.56mm M4A1, the replica has a fire selector switch marked Safe, Semi and Auto, although this gun only offers semi-auto blowback. With the switch on Safe, the mag can be seated in the well, after which the gun is now ready to fire. 

Pulling back the charging handle will automatically open the spent case ejector cover, another feature that’s not needed on this airgun but is nice to have nonetheless.

As with the original M1A1 Carbine, the M16-style carrying handle can be removed, revealing a Picatinny rail underneath
The mag that hold the BBs and CO2 is hidden inside an outer shell that makes the whole thing look like the standard 30-round 5.56mm box magazine

Brothers In Arms recommends using only steel BBs, so my testing began with BBGold! ammo from Lee Enfield (Guns), but I felt I should experiment with other types too, including the low-ricochet Smart Shot BBs and frangible Dust Devils. 

All types worked perfectly, although the best accuracy was attained with the BBGold! When shot rested at 10 metres, accuracy was around the size of a rabbit’s head, which might not sound impressive, but this is from a blowback BB gun costing around £160, and using open sights.

I shot the M4A1 kneeling and standing, and accuracy remained about the same, with my rabbit’s head spinner making a pleasing “tink” with each pull of the trigger. 

One thing that struck me immediately during use was how quiet this gun is. If you’re planning on shooting in your garden, then the M4A1 is a good choice as it’s very neighbour-friendly. 

All my testing was carried out outdoors on very cold days, but I averaged around 60 shots per CO2 capsule, which I was pleased with.

I find airguns like this M4A1 to be interesting on a number of levels. First of all, it’s fun to have an airgun that fires BBs and looks “real”. 

Secondly, they can appeal to collectors for whom a deactivated original is simply too hard to come by. Third, they can be a great training tool for anyone with a Firearm Certificate who wants to buy a powder-burning AR-15-style rifle. 

Over here, that means a semi-automatic AR in .22 or a straight-pull single-shot action in any other calibre. It can also be a good way of getting to grips with the ergonomics of the FAC rifle before deciding whether or not it suits you. 

If the Brothers In Arms M4A1 Carbine appeals for any of the above reasons then I’d suggest taking a closer look, especially considering its low cost of ownership.

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