Tag Archives: H&K

Two Great Videos Explaining How Roller Delayed Blow Back Actions Work

I’m a fan of the Roller Delayed Blow Back firearms for a while and have had opportunities to own and shoot ones from HK, POF, and PTR. I knew the rollers were locking the bolt head in place but never really understood the details of the action. I’ve tracked down two great videos to help show you what is going on.

This is a PTR PDWR in .308 – basically a cut down HK-91 style pistol with a SB Tactical SOB Brace and a Vortex Optic.

Forgotten Weapons

In this short video, Ian @ Forgotten Weapons does a great job explaining just how this system works.


This is one of MouseGunner’s cool x-ray renderings where he shows the MP5’s action at work. He’s done this for other weapons as well and watching the weapon operate really helps.

I hope this helps you out. Be sure to subscribe to both guys’ channels – Forgotten Weapons and MouseGunner.

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HK SP5K Photo Shoot In The Leaves

Okay, I liked the leaves, the lighting and thought it would be a great chance to get some photos of the HK SP5K pistol with the SB Tactical SBTK5A brace and the Vortex Optics Crossfire red dot that is on an American Defense AD-T1-L STD quick release mount.  As you can see above, I’m still using the Uncle Mike’s case.

So those are a few from the batch.  Looking forward to taking it to the range some day.

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Basic SubGun Case for HK SP5K with Brace

As I wrapped up my changes on the SP5K, I realized I needed a case to put it in.  It just so happened that I had an Uncle Mike’s “Tactical Submachine Gun Case” that I had never used and it turns out the SP5K with the SB Tactical SB5KA brace and Vortex Crossfire red dot could slide right in without the magazine installed.

This is the front of the bag – six magazine pouches, one large flat pouch to the front and the rear mounted carry handle is visible.
This is the back – you can see the shoulder strap and the carry handle at the top.

The case has a zipper at the rear of the bag and the SP5K simply slides in.  This is one thing I dislike – it does not open and lie flat.  Some folks may find this a plus but I prefer bags that open.

The exterior dimensions are 24.5x14x2 and I’d knock off about half and inch all the way around for the interior dimensions.  It does have some padding but not a ton.

Another dislike I have is the way it holds the MP5 magazines.  They slide down in the little pouches and I can’t pull them out.  I need to push at the bottom to get them to slide up.

I pushed the magazines up so you can see them in this photo.  Notice where the bulges indicating the actual lower part of the magazine in each pouch.  In practice, the mags slide all the way down and are hard to get out.  You have to press from the bottom.

On the topic of pouches, the front pouch just forward of the magazines is very tight.  The bulge you see sticking out is a Mag Lula loader.  While it can hold the loader, it’s really better suited for thinner items.

Okay, rounding out my complaints, the carry handle at the rear makes for an odd front-loaded unbalanced load.  I don’t know why they didn’t center it.


It’s a decent entry bag for only $27.95 with Prime shipping on Amazon.  Sure there are things I don’t like about it but does the job.   I will be investigating other cases but this case is a solid performer at the price.

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Picking an Optic for HK SP5K

In past posts, I have written about buying the SP5K, selecting a brace and the forearm.  Next up is the optic.  It should come as no surprise that my go to brand is Vortex Optics.

I’m a creature of habit.  Vortex products are solid and have a no-nonsense – “if it breaks we will fix it” – warranty.  Vortex does not sponsor me so I have no reason to stick with them other than they deliver.

I knew right way this was going to be a close-in weapon with distances being typically 25 yards or less but maybe stretching out to 50 yards.  It is hard to beat a red dot at those distances for rapid target acquisition.  That narrowed my options down quite a bit.

A second big deal for me is to have a wide field of view but also a relatively small dot size.  This combination rules out a lot of the micro dots that are out there as they are both tiny and have a 4 MOA dot size – that means the red dot will cover 4″ and 100 yards or about 2″ at 50.  The micro dots are okay and I rather like them on pistols but I wanted something a tad finer on this more controllable and accurate weapon.

The Vortex Crossfire Red Dot

All paths lead me to the current Vortex Optics Crossfire red dot. It has a 2 MOA dot size, is only 2.5″ long and only weighs 5.2oz.  It also has a battery life of 7,000 hours at an output setting of 5.  Note the optic has 11 levels so when you have it turned up for bright light settings, you will drain the battery faster – always keep a spare battery in the case.  I’ve had a couple of range sessions get messed up to do dead/dying batteries and no spares.

American Defense AD-T1-L STD Mount

The only shortcoming, if I can even call it that, with the Crossfire is its base.  Vortex did their homework and include both a short base and base that can lower 1/3 co-witness with AR iron sights.  The problem is that they are screwed onto the picatinny rail.  If you need to get the optic off fast, that’s not going to happen as you will need a torx driver.

I do have good news – the Crossfire has the same base geometry as the Aimpoint T-1/H-1 optics.  That’s the key right there – there are a lot of mounting options out there and after some digging, I have been using mounts from American Defense for over a year and they are rock solid.

By the way, make sure you get the right mount – American Defense makes there base for a variety of optics.  I am using the AD-T1-L STD.

Assembling the Optic on the Mount

The good news is that this is really easy.  Undo the four screws on the bottom of the Crossfire to remove the Vortex mount.  Put the American Defense mount underneath it, add a bit of Blue Loc-Tite thread locker and reinstall the screws.

Use the small Torx wrench that Vortex supplies with the Crossfire to remove the four screws so you can the swap the bases.
Here you can see the bottom of the Crossfire and how the American Defense mount will align.
You can see the Blue Loc-Tite and the installed screws.  I like to put the Loc-Tite in the holes and then install the screws.  I wiped the residue away with a paper towel after I took this photo.

The Result

The result turned out really nice.  The optic is just the right height that it is relatively close to the bore and I can get a good consistent cheek weld.

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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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Brace Options for the HK SP5K

In the last post, I told you I bought an HK SP5K.  It’s relatively heavy and begging for a brace.  I don’t really feel the need to spend the money and wait to register it to be a Short Barreled Rifle (SBR) and there are actually a ton of arm brace options out there. 

Option 1:  The SBT5KA Brace

I have a SB Tactical SBT5A Brace on my POF-5 and really like it.    I knew they made a version for the SP5K known as the SBT5KA but I was hoping for something different. Please note they are two different models of braces reflecting the different receiver end caps.

Option 2:  The SOB Brace

Every time I write this product name – the “SOB” – down, I smile.  SB Tactical has a ton of braces for the AR/M4 weapons family and they have evolved a ton away from the ugly original.  The SOB has clean lines and I run one on my PTR PDWR.  I think it looks good and has handled the .308 rounds from the PDWR just fine and feels solid too.

Option 3:  The SBPDW

I thought I had found just what I wanted with the SBPDW – a collapsing stock that looked really slick and it would be easy enough to add an M4 adapter to the SP5K.  So, I ordered a very well made adapter and the expensive SBPDW stock and guess what?  It would not fit.

Needless to say, I was bummed.  I had it completely installed only to find out that the guide rods on the SBPDW run right into the sides of the SP5K.  Crud.  I didn’t feel like figuring out all the changes that would be needed.

Purely for reference, here’s the same PDW brace now installed on a 10.5″ AR Pistol but that is a story for another day. It is a rock solid brace.

The Winner?  The SBT5KA

Well, I was bumming from the strike out with the SBPDW so I went with my second pick – the SBT5KA.  I felt it was most true to the lines of the MP5K and ordered one. As with their other braces, SB Tactical did a great job.

Installation was a breeze.  Pull out the two small pins at the back, swap the old end-cap for the brace, push them together and reinsert the pins.  I did make sure the recoil rod lined up and nothing was binding as I reassembled the unit.

I Did Clean and Lube The Internals

I should point out that when I removed the end cap, I went ahead and slid out the bolt group and lubricated everything.  I applied Super Lube grease to the bolt body and Mobil 1 Synthetic 10w30 via a precision oiler to the rollers of the bolt and rotating surfaces.  I also oiled the pins on the trigger pack while greasing the hammer face with Super Lube.


So you see I went with the SBT5KA brace.  In the next post I will discuss handguards.

Note, I have to buy all of my parts – nothing here was paid for by sponsors, etc. I do make a small amount if you click on an ad and buy something but that is it. You’re getting my real opinion on stuff.

If you find this post useful, please share the link on Facebook, with your friends, etc. Your support is much appreciated and if you have any feedback, please email me at [email protected]. Please note that for links to other websites, I may be paid via an affiliate program such as Avantlink, Impact, Amazon and eBay.

So, I have an HK SP5K …

Folks, I have thoroughly enjoyed my POF-5, which is an MP5 pistol clone, this past summer.  We easily put way past 500 rounds through it with zero failures to feed or eject.  All my family members and friends wanted to shoot it and we had a ton of fun.  However, in the back of my head, there was a little voice saying “you need a real HK”.

Finding a Real HK

I’d talked to a few guys and the consensus was that a real HK will just go up in value even after being shot plus there are the bragging right of owning a real HK.  There was one problem – HK stopped making MP5s available for civilian sales.  There are definitely a lot of parts kits out there but then someone needs to pay an HK smith to assemble the subgun.  I thought about doing it but I lack the experience and the tooling.  Given the price $1,600-3,200 price of kits, I wasn’t about to experiment.

It turned out that HK still made a civilian pistol – the SP5K – “Sporting Pistol” 5K – that is a semi-auto version of the short MP5K submachine gun.  The one catch is that it comes to the US market a tad neutered.  Surprisingly, this was done due to strict German export laws and not US import laws.   For me, the sad part is that the barrel is 115mm/4.53 inches long and ends abruptly at the sight block – not only is there no threading or tri-lug attachment point but the abrupt end means you can’t add one either without replacing the barrel.  However, accuracy reports are excellent so at least that and reliability were still there.

Before I seriously considered buying one, I did some research:

There are also some choice articles:

Hard to Find an Affordable SP5K

Of course, these things aren’t cheap and they are really hard to find in stock.  I hunted around online while my FFL, Scott Igert of Modern Antique Firearms, did the same.  After hunting for a few weeks it dawned on me that I would need to use GunBroker.  So, I started by watching auctions and seeing what stuff sold for before I started actually bidding and losing.  I learned a while ago not to chase auctions – set a price and don’t go past that limit.  I finally found a deal after watching and bidding for over a month. 

So, the seller was Town Police Supply, located in Collinsville, VA, who goes by GunTalker on GunBroker.  They had an A+ reputation with over 700 trades.  I always prefer to deal with sellers that have a lot of trades.  At any rate, they were great to deal with.  I won the auction on 9/24/18 and it arrived at Scott’s shop on 9/25.  Literally.

As you can imagine, I picked the SP5K up as soon as I could.  It came in a real cool HK hard case with two 10 round magazines, a sling and a sight adjustment tool as you can see in the featured photo at the top.

Here’s the plain pistol out of the box:

In summary

So, it was definitely cool but if you know me, you also know what was going through my head – “I can customize this!”  In my next blog post, I’ll talk about what I considered for braces.

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Amazon product links are at the bottom of the blog.

Customizing and Shooting the Pakistani Ordnance Factory POF-5 Pistol

Having watched one too many TV shows and movies with H&K’s MP5 submachine gun over the years, the sub gun has been on my “I want to have one list” for years but way out of my price range.  While surfing, I read about how Pakistani Ordnance Factory (POF) licensed the design and tooling necessary from H&K Germany to make roller locked weapons including MP5 clones.  In reading about the various Mp5 clones,  it became apparent that the POF-5 units are actually well regarded.  What really tipped the scales was a great post by T. Mark Graham at Arizona Response Systems who really knows his way around MP5s saying they were good to go with details of his analysis provided.

This led me to calling up Chuck at Kelly Enterprises and talking about whether to buy a Zenith (my first choice) or a POF.  Chuck is a very straight forward guy and tells it the way it is.  The Zenith would be hard to get and he had POF-5 pistols in stock plus he gave me a great deal so I ordered one and had it sent to my friend and FFL, Scott Igert, at Modern Antique Firearms.  Chuck sent me all the tracking info and just a few days later, the POF-5 was with Scott waiting for me to pick it up.

On inspection you could tell the receiver paint was a bit glossier than the more satin finish of an HK but other than the action feeling dry and new (that gritty not worn in feeling), it looked good to go.

Now, I have two personality quirks.  First, I can’t hit the broad side of a barn with a pistol let alone one this big and heavy.  Second, I can’t help but customize any gun I buy and this wasn’t any different.

I did a ton of reading and decided to go with a cool S&B brace, a B&T scope mount, Dakota Tactical handguard, a B&T muzzle brake and ordered a bunch of POF MP5 magazines.  You can buy the brace at PSA and Brownells. By the way, Brownells has a ton of replacement parts and aftermarket parts for the MP5 reflecting it’s long-time use by law enforcement no doubt – click here to see them.

Installing the brace was easy – like any HK, you push out the rear pin, pull off the cap and put on the brace.  I bought one all ready to go.

The handguard is a keymod unit from Dakota Tactical and they use a screw instead of a front pin to hold the unit in place.  It really locks up nice and I like the feel of it.  The rail section holding the Streamlight in the below photo is made by Monoki.

Now the scope mount is the standard B&T universal rail, the BT-21262-1.  I would caution against you buying a cheap optics mount for an HK-type weapon.  There are tons of stories of cheap ones falling off, not seating properly, etc.  The B&T unit is a mil-grade unit.  You slide it on and then work the little claws or feet into position and then secure them with the supplied screws.

Next up  was to install the Vortex Crossfire Red Dot optic.  These are the latest red dots from Vortex and come with both low and high mounting options.

Out of the box it has the high mount installed for the AR enthusiasts but includes the low plate as well.

As you can see, with the default high riser on it, the optic is way too high.  I prefer optics as low as possible where I can get a good cheek weld.

It’s real easy to change – there are just four screws that need to be removed on the bottom.  I used a bit from my Weaver driver set vs. the supplied key which would work but is slow compared to a driver.

I have the Weaver Deluxe Tool Kit and use the drivers all the time.  I use the block and hammer some but not a great deal.

Notice that Loc-Tite Blue (the medium strength formula) is used to secure the screws.

Here’s the end result.  Note, I will install a quick release mount at a later date.

One side comment – you may find it funny that the thing that puzzled me most was the B&T brake.  It installs on the tri-lobe fitting on the muzzle. There is a quick release lever that baffled me until I carefully inspected it and saw that one end is open and a cross pin is retaining it.  I then pushed the other way and lever lifted right up.  Duh!  I’d never seen one before!  It is solid and I like it.

The case you see is a 32″ Blackhawk Homeland Security Weapons Carry Case.  It comes with one internal mag carrier and I added a second pouch.  They are sized for 30 round AR mags and you can get two 30-round MP5 magazines in each pouch pocket.

Next up, I cleaned the bore and lubricated the weapon – especially the bolt head and trigger pack.  Past experience taught me to go through and make sure it was ready.

Two of my brother-in-laws and I took it to the range.  We used 124 grain S&B FMJ ammo and it functioned great and was accurate.  We had a blast at 15-25 yards shooting it despite it being a brisk day.  I really like how this combination worked out.  We didn’t use the light but the green laser was nice and bright when we tried it out.

We put probably about 200 rounds through it.  You can now feel the action has really smoothed out and I wouldn’t hesitate using this for home defense if I needed – which is why I put the light on it.

All in all, I’m very pleased and would recommend the POF-5 to anyone looking for a semi-auto MP5-type pistol.

Update 10/6/2018:  We put almost 500 rounds through this pistol this summer without one single failure to feed or eject.  We mainly shot the 124 grain FMJ S&B ammo except for one time, as a test, I shot about 20 rounds of Hornady 135gr Critical Duty ammo with no problem.  All of the magazines used (and I have 10 of them) are POF magazines.  Honestly, this thing is awesome.  I’ve only cleaned and re-lubed it once so far but it is on the to-do list.

12/12/18 Update:  I recently bought an HK SP5K and am documenting my journey with it.  Click here for the first post.

If you find this post useful, please share the link on Facebook, with your friends, etc. Your support is much appreciated and if you have any feedback, please email me at [email protected]. Please note that for links to other websites, I may be paid via an affiliate program such as Avantlink, Impact, Amazon and eBay.