The arrival of HAO’s monolithic upper (part 1) was something of a surprise and it’s a great honour to be one of the first to handle this beta release.

It’s caught me short, however.

I’m waiting on a new armourer’s hammer right now (for the various roll pins) and the return of my upper receiver block, so that I can crack on with assembling the upper.

I’m also waiting on a few additional items which HAO is going to send to me once manufactured – including a replaceable charging handle latch ‘notch’.

This is a steel insert, which will be tapped into the rear of the receiver, here:

So for part two of this series, I thought I’d look at the kit’s components in more detail. Readers may be interested to learn that HAO is going to sell certain parts and sub-assemblies as individual products – like the gas block, for instance.

OK – the latter is hidden from view, but I’m sure some of the more details-orientated A2 builders will relish the opportunity to add just a touch more to their builds.

HAO’s IUR features a 10″ outer barrel:

As usual with HAO receiver sets, the upper comes with a good quality birdcage flash hider as a placeholder – although you’ll probably want to replace this with the appropriate Surefire FH556-216A at some stage.

A real steel 216A will fit straight on, but an airsoft substitute will need to be rethreaded to RS specs.

The barrel itself is the correct profile and is marked thus:

The flash hider end of the barrel features flats, where the gas block’s grub screws locate. There’s also a recesses where the gas block’s anti-rotation tabs are held.

The gas block, of course, exhibits corresponding features. The gas tube is pinned in place as usual.

The barrel nut slides over the barrel and threads into the receiver. My kit includes a special tool to achieve this.

The business end of the tool is equipped with tiny magnets, which allows the barrel nut to be held on, while the tool subsumes the barrel.

Needless to say, the tool is a hollow cylinder which is longer than the barrel. It has flats for a crow’s foot wrench.

Precise fit is really important for the Systema PTW and the tolerances are spot on. That’s unquestionable with a HAO product, but still worth mentioning for those who are unfamiliar with the brand.

The receiver itself is also highly impressive and is unlike any other AR upper out there. Not just because it is defined by its monolithic form factor, but because of the way it deals with problems like ejection port cover fitting.

HAO’s L119A2 IUR features the same structures as the real deal, within which the cover is pinned. To remove the pins, they must be fully knocked through – into the hollow body of the receiver; exactly the same as the RS.

HAO has included a C-clip with its ejection port cover, but since this is not a feature of Colt Canada’s excellent design it should be dispensed with.

The grenade lug is also faithfully reproduced as are some of the more difficult to produce features:

Another Colt Canada design feature – mentioned earlier – is the replaceable charging handle notch. This is the area where the latch bites. You can also see the stepped end of the receiver in the pics below.

As for markings, the following are present –  I love a bit of embossed…

Many will attest that markings are some of the most difficult things to replicate. My only note here is that I would have preferred the patent markings to be absent – but as one of the leading lights of the UKSF impression scene said to me, it’s not a deal breaker.

I think the embossed “Colt Canada 2C085” markings could be fatter and more rounded. That said, I’ve never seen a real IUR, so what do I know?

HAO also supplies a charging handle, but it’s one of their spring loaded ones which I’m not keen on. It makes a good placeholder, however.

This is an impressive upper which I think even eclipses HAO’s benchmark HK416A5.

Catch up on the full HAO IUR series

The Comprehensive UKSF (SAS/SBS) L119A2 Parts and Accessories List