Dragging things out, or taking it slowly so I don’t fuck it up? You decide.

Today I’ve mainly been smashing roll pins into the dirty chunk of 7075 T6 that is HAO’s L119A2 IUR. Aside from a ball clenching moment with the forward assist, it’s gone pretty well.

Massive UJ Velcro patch from Britkit USA, Colt Canada sticker from Jay Taranis (thanks both!)

First on today’s list was the hack job I mentioned in Part 3 of this series: cutting down the dummy gas tube, which extends too far into the receiver to for me to install a generic RS Colt charging handle; purposed as the gas tube is for HAO’s sprung effort.

Could I find my hacksaw? Not even a junior one. So I had to break out the big guns which got the job done, but really isn’t recommended.

Fitting the gas block onto the gun drilled steel outer barrel is very easy, thanks to Colt Canada’s design which HAO has reproduced.

The gas block is self-centring thanks to its locating tabs, then you just use an Allen key to secure the two bolts on the underside. I’d already fixed the gas block to the dummy gas tube, with the small roll pin included.

Just to note:

If you stick with the included charging handle, the process is different. You must install the gas block alone, first, then insert the dummy gas tube in through the receiver. You then secure the tube in the gas block using the roll pin (it’s accessible using a punch through the rail). Just make sure before you start that the gas tube inserts freely into the gas block and lines up correctly with the roll pin hole.

This didn’t apply to me, but it was a tip off from Tackleberry.

Next up was the most enjoyable bit – the ejection port/dust cover install.

Like the charging handle, I wasn’t 100% happy with the dust cover that HAO provided in the kit. There’s nothing fundamentally wrong with it, but I had a spare RS Colt version that I wanted to use as I prefer the patina.

I also prefer to have the dust cover in the closed position, which you can’t do unless you obliterate the dust cover latch.

I ended up using the RS Colt spring too, as it was stronger – but I installed the HAO dust cover axle as it’s a touch fatter and makes the assembly more solid. The C-clip is not required for this install, although HAO provided one.

You can tell the real deal L119A2 IUR is a premium product, because of the way it’s designed. There are no shortcuts. Taking on the problem of installing the dust cover – faced with the monolithic design – LMT (owners of the monolithic patent) did something totally different and probably not cheap.

The dust cover’s axle slots into recesses in the receiver and secures with roll pins. The roll pin holes extend all the way through the receiver, so if you need to remove them just take out the internals and smash the pins straight through so they drop out into the hollow. That’s only possible with one roll pin with the barrel installed, but you only need to remove one roll pin to remove the dust cover.

Big thanks to E27R for letting me know that this is an LMT design feature and not one of Colt Canada’s own.

Ready for install with mallet, punch and roll pins:

I didn’t anticipate using my receiver block for the dust cover install, but it supported the receiver really well while I bashed the roll pins in.

Again, this was an absolute pleasure to work on and Colt Canada’s design ingenuity – not to mention HAO’s tolerances – shone through.

Lastly, the forward assist install. This is complicated by the forward assist button being under pressure from its spring.

I turned the receiver upside down so that it lay on its 12 O’clock RIS and supported the forward assist housing underneath (I Frog-taped a strong plastic structure to it).

I started to install the roll pin (an evil, fat one) without the forward assist and spring in place. When the roll pin was just about to breach the forward assist housing’s void, I inserted the forward assist button and spring and orientated the flat of the button accordingly.

It’s a three handed job, but if I can manage it anyone can. I would say that having decent tools help, though.

The only thing missing now in terms of roll pins are a couple of cosmetic ones. I need one for the forward assist button, which HAO doesn’t supply. I’ll get an RS one when I can.

I also need one for the end of the rail. In the RS, this fixes the gas tube in place at the receiver end, but it’s simply a nice to have in HAO’s replica.

They will provide a roll pin for this with the production model, I’m told.

I continue to be impressed with this upper. To date, it’s the best I’ve encountered for PTW – and that’s not because I’m a huge fan of the L119A2 and UKSF, but because it’s so well executed.

Catch up on the full HAO IUR series

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