Deciding on the Forearm for my HK SP5K

In my last post, I went over the options I considered for the brace on my HK SP5K.  In this post, I’ll review the three handguards I looked at – the original forearm, a US-made polymer unit with an integral hand stop and a low-profile aluminum unit.

I really have two places I shop for HK and related parts – HKparts.net and RobertRTG.  So I went and checked out what they had plus I did google searches on “SP5K photos” and “MP5K photos” to see what others were using.  I’m a visual guy and can scan a ton of photos very fast and then click to read the articles.

Removing the handguard is pretty much like all other HKs – pop the pin and pull down.  You can see just how short that barrel is due to HK having to comply with German export laws for the pistol to be deemed “sporting purpose.”  This also means you need to carefully think how to keep your fingers, notably your thumb, out of the way.  You could argue training and holding the mag well but… there is a risk no matter what.

After researching for a bit, I got it down to the following three options that I could afford to try out:

Option 1:  The Original Forearm

The unit that comes with the SP5K has two things going for it – the hand stop and the muzzle guard.  The little indentations you see on the sides are actually thumb rests.  From a safety perspective, this seemed like the best but I wasn’t sure about how the muzzle protector would hold up over time.

Note the thumb rest of the muzzle guard area of the original SP5K handguard.  The hand stop is well forward giving you plenty of grip options also.
See, the actual end of the muzzle is located way down in the guard.  I can’t help but wonder how the polymer will hold up over time.  I’m betting HK thought about that is why they made the guard so much wider than the muzzle to allow most of the blast cone to pass by without contacting the polymer.  I haven’t heard of folks having problems so HK must have designed it correctly.

Option 2:  A US-made Polymer Handguard Sold by HKParts.net

The second option I decided to try was a US made “Reverse stretch forearm with hand stop” that was made for HKparts.net.  It was very well, fit my SP5K great and had great room for my hand but the problem was my thumb.  It wanted to go in front of the muzzle.



To be clear, it is an excellent handguard.  I blame the German politicians for the abrupt barrel.  If I had a muzzle device out front, this would have made an excellent forearm.

Option 3:  HKParts.net’s Own Low-Profile M-Lok Unit

So this brings us to the last option.  I tend to like the flexibility that rails bring and decided to try another HKParts.net model – their Low Profile Forearm M-LOK.  I ordered an Ergo hand stop/barricade stop to mount on it as well. 


I removed all of the screws to install the unit just in case some wiggling was needed. I think it could have fit without my doing this but I was trying to save the finish.
I knew I was in trouble.  It was going to be way too short and the Ergo hand stop was going to be pushed back into a slot and not going to be able to protrude without some machining.
The Ergo hand stop / barricade stop was well made.  No complaints at all with that part.  It installed just like any M-LOK component does.
Here you can see that the Ergo’s position is constrained by the M-LOK design.
Houston, we have a problem.  I wear XL-sized gloves found the resulting set up way too awkward.  I thought about drilling and tapping the handguard to move the Ergo forward but then I would still have my thumb flopping around.

Bottom line, this just was not going to work as much as I wanted it to.  Blasted politicians.

So What Did I Do?

After trying all three out, I decided to actually stay with the original forearm.  Some day in the future, I will spend the money to have a B&T barrel installed with a tri-lug adapter.  I really like the B&T brake that I run on my POF-5 and will then decide on which of the handguards I want to use.  So, the brace and handguard were both selected, in the next blog post, I’ll discuss the optic I went with and why.

Here she is for the moment.  Note I added a QD Swivel to the mounting point on the brace. 

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