I’ve been using a Super Modular Rail (SMR) on my M4 for about a year. It’s a MKII, which is my favourite M4 version. However, there’s always been that special instance of the SMR; the one which started it all. The one which is tacitly agreed to be just that one rung higher in coolness stakes: the HK SMR.
Well, I’ve had opportunities to source one before, but I wanted to wait until a UK dealer bought some in.
I thought I’d document a few of the features I’ve noticed.
Firstly, aside from the need to remove the sling loops from the gas block, the HK SMR is a drop in fit for my HK416 PTW upper. Sling loop removal is common to the RS, too. In fact, Geissele’s instructions, which are included with the rail, even suggest how to do it. I used a hack saw. Ghetto.
The HK SMR utilises the original HK 416 barrel nut, so Geissele does not include this item.
A lot of thought has been put into this rail. The cross bolt, which intersects with the barrel nut and retains the rail, is redesigned. It is held semi-captive within the rail, which means when open it won’t fall out unless you mean to remove it.
The threaded insert into which the cross bolt screws has a thread locking mechanism and comes complete with a slick of copper lubricant, to stop the threads from seizing.
However, if preferred the original HK 416 cross bolt can be used.
The rail exhibits a pair of excellent QD sling swivel sockets, which are a must for two point sling users.
These have steel inserts, which are rotation limited. The inserts are set at 45 degrees to the vertical. I actually prefer these sockets to the Magpul RSA I’d been using. They are placed closer to the rail and just stay out of the way.
I wouldn’t now use a QD socket which wasn’t rotation limited, so I’m glad Geissele included this feature.
Because of the striated texture of the rail, in terms of CNC work it looks unfinished in certain areas. This produces a wood grain effect, which I read somewhere was requested so that the rail afforded some grip, when wet. Regardless, it looks unique.
Unlike a lot of tube rails (I have owned quite a few), where the modular RIS sections are a PITA to attach, the HK SMR uses threaded steel inserts:
RIS sections are simply screwed straight in, with no messing around with backing panels.
Lastly, because the HK SMR is a tube rail, it’s a big improvement over the standard HK416 RIS in terms of handling; and it enhances the feel of the whole gun.
This is achieved simply by changing the ergonomics and affording lower drag at the front end. It really is transformative in this way, as well as aesthetically.
For example, the HK SMR sits in the hand:
The original 416 rail is quite a handful in comparison:
Given that I already own an SMR, I wasn’t ready to be overly impressed by the HK version, but I am.
I like my 416 PTW more with the SMR installed and that’s all anyone could ask for, really. The fact that the HK SMR has all these additional cool features and makes weapon manipulation easier is a bonus.
The Reptile House 