HK433 Generation 5

[BarnOwlLover]

This is one modern rifle that I'm insanely interested in, especially since there was a TFB article that hinted that there was a .308 Winchester/7.62mm NATO version being worked on that might use the same upper as the 5.56mm NATO version that HK has shown in several different versions since 2017. 

 

This is the latest (known) iteration of the 433, and if you've seen some of the POTD posts at TFB since May of last year, you've probably seen it a time or two.  In short, the 433 is HK's answer to the FN SCAR and to try and one up it.  IMO, the most interesting thing about the 433 is that it seems capable of taking way more caliber rounds than items such as the FN SCAR or the Bren 2, which needed new uppers in order to go rounds like .308. 

 

Out of curiosity one day, since I've seen numerous (though not often very new) photos of the 433 and I've also seen patent documents (I'll provide a link to patent documents and an article on Spartanat with some photos of the Gen 5 433), I decided to see if my own thoughts on the 433 being caliber convertible beyond .300 Blackout or 7.62x39mm held water.  Using a simple image scaling and measuring program, I've determined that the 433 upper, as is, is capable of taking rounds or at least magazines of 71-72mm OAL.  Mind you, this isn't exact, and I was conservative with my measurements. 

 

Of course, this does further peak my curiosity on what the 433 is capable of firing and how caliber convertible it may be.  On top of of course how it comes apart and various details about it.

 

Now the documentation.  Spartanat is an Austrian site, and hence is in German, and being new here I'm not sure how Google translate works when linked, so I'll just leave the link (which has good, albeit sadly not ultra HQ/high res images, which IMO is a damn shame) to be copypasta'd into Google's translator or your favorite translator.  On the plus side, there's a PDF in the article that you can save or convert to a pretty high res JPG or PNG image, and Google does a decent job of translating the PDF, too:

 

https://www.spartanat.com/2019/05/photo-file-hk433-mit-concamo-im-feld/

 

Now here's the patent documents and images.  This series mostly pertains to the charging handle system, but it shows a good idea of how the guts of the 433 are laid out:

 

https://patents.google.com/patent/DE102018001984A1/en?inventor=Wilhelm+Fischbach

[Collimatrix]

1 hour ago, BarnOwlLover said:

This is one modern rifle that I'm insanely interested in, especially since there was a TFB article that hinted that there was a .308 Winchester/7.62mm NATO version being worked on that might use the same upper as the 5.56mm NATO version that HK has shown in several different versions since 2017. 

 

This is the latest (known) iteration of the 433, and if you've seen some of the POTD posts at TFB since May of last year, you've probably seen it a time or two.  In short, the 433 is HK's answer to the FN SCAR and to try and one up it.  IMO, the most interesting thing about the 433 is that it seems capable of taking way more caliber rounds than items such as the FN SCAR or the Bren 2, which needed new uppers in order to go rounds like .308. 

 

Out of curiosity one day, since I've seen numerous (though not often very new) photos of the 433 and I've also seen patent documents (I'll provide a link to patent documents and an article on Spartanat with some photos of the Gen 5 433), I decided to see if my own thoughts on the 433 being caliber convertible beyond .300 Blackout or 7.62x39mm held water.  Using a simple image scaling and measuring program, I've determined that the 433 upper, as is, is capable of taking rounds or at least magazines of 71-72mm OAL.  Mind you, this isn't exact, and I was conservative with my measurements. 

 

 

Could you show us these measurements?

[BarnOwlLover]

Measurements are in millimeters.  Upper measurement is OAL, lower measurement is length of the rear of the front trunnion to approx end of mag well:

 

 

The position of the TE of the rear turnnion was determined from this:

 

[Collimatrix]

And what result do you get if you use the same measurement methodology with a picture of a Bren 2?

[BarnOwlLover]

[Sturgeon]

Well within margin of error.

[Collimatrix]

So, even assuming that the trunnion to the rear of the magazine well is the primary limitation of the size of cartridge a rifle can handle, why do you think that two milimeters is going to make all the difference?




 

Look carefully at this comparison of a SCAR-L with a SCAR-H.

[BarnOwlLover]

The thing that has to be remembered is that the SCAR was broken up into the L and H variants, or basically 5.56mm and 7.62mm NATO.  The H has an upper that's nearly an inch longer than the L variant, let alone much wider.  Also, considering that most of the caliber conversions (such as 7.62x39) have focused on the H variant, I've wondered and come to think that the L is optimized around 5.56mm.  I actually can't remember there being any caliber conversions offered for the SCAR 16 aside from .300 Blackout. 

 

What has gotten me thinking about the 433 maybe being 7.62mm NATO compatible with a lower, barrel and bolt swap is, one, the TFB article referring to it.  But I've also been told on HK Pro that, for instance, HK were shown or at least informed of the concept of the POF .308 chambered AR-15 upper.  That's what got me thinking about seeking out an online image scaler/measure feature. 

 

Which brings me to Sturgeon saying that it's well within margin of error.  Emphasis on the word error on my part.  I'm very, very doubtful that my measurements are exact.  Also, I haven't been able to locate the length front to rear of a .308 HK mag or SR-25 mag.  Granted, I've measured a few photos of the 433 in the same method, and though the measurements haven't come out exactly the same each time, they've fallen into the same 71-72mm range.  Which given variations in photos, my un-steady hands and crappy eyesight, can maybe be considered a preponderance of evidence (?). 

 

Of course, if the 433 can take .308/7.62mm sized rounds in terms of width and length, that can open up a lot of things, given that the 433 would be a pretty compact rifle for barrel length in those larger calibers. 

 

Granted, all the 433's that have been show are not only in 5.56mm, but are marked as 5.56mm on the upper, though the rifles shown are basically the versions they're trying to pitch to the German Army.

 

 

[Sturgeon]

12 hours ago, BarnOwlLover said:

The thing that has to be remembered is that the SCAR was broken up into the L and H variants, or basically 5.56mm and 7.62mm NATO.  The H has an upper that's nearly an inch longer than the L variant, let alone much wider.  Also, considering that most of the caliber conversions (such as 7.62x39) have focused on the H variant, I've wondered and come to think that the L is optimized around 5.56mm.  I actually can't remember there being any caliber conversions offered for the SCAR 16 aside from .300 Blackout. 

 

What has gotten me thinking about the 433 maybe being 7.62mm NATO compatible with a lower, barrel and bolt swap is, one, the TFB article referring to it.  But I've also been told on HK Pro that, for instance, HK were shown or at least informed of the concept of the POF .308 chambered AR-15 upper.  That's what got me thinking about seeking out an online image scaler/measure feature. 

 

Which brings me to Sturgeon saying that it's well within margin of error.  Emphasis on the word error on my part.  I'm very, very doubtful that my measurements are exact.  Also, I haven't been able to locate the length front to rear of a .308 HK mag or SR-25 mag.  Granted, I've measured a few photos of the 433 in the same method, and though the measurements haven't come out exactly the same each time, they've fallen into the same 71-72mm range.  Which given variations in photos, my un-steady hands and crappy eyesight, can maybe be considered a preponderance of evidence (?). 

 

Of course, if the 433 can take .308/7.62mm sized rounds in terms of width and length, that can open up a lot of things, given that the 433 would be a pretty compact rifle for barrel length in those larger calibers. 

 

Granted, all the 433's that have been show are not only in 5.56mm, but are marked as 5.56mm on the upper, though the rifles shown are basically the versions they're trying to pitch to the German Army.

 

 

 

You need to stop this nonsense and start contributing. Nearly every relevant thing you said is incorrect,  misconceived, or misapplied.

 

It is tiresome to have someone here who is so verbose and so erroneous at the same time. It takes a lot of time to refute it all, and we are no longer young, patient men with nothing but.

[BarnOwlLover]

I'm just explaining what I've been told by others elsewhere.  I'm ready and willing to learn as well.  However, if that's not desired here, I'm ready and willing to leave.

 

I've read the forum rules and requests, and I'm doing the best I can with what I know.  If that's not good enough, all you have to do say please go pound sand.

[Sturgeon]

39 minutes ago, BarnOwlLover said:

I'm just explaining what I've been told by others elsewhere.  I'm ready and willing to learn as well.  However, if that's not desired here, I'm ready and willing to leave.

 

I've read the forum rules and requests, and I'm doing the best I can with what I know.  If that's not good enough, all you have to do say please go pound sand.

 

Ok, if you're honestly interested in learning, try talking less authoritatively. Asking questions is fine. As an example: 

15 hours ago, BarnOwlLover said:

The H has an upper that's nearly an inch longer than the L variant, let alone much wider.

 

This is an authoritative statement. It's also wrong. If you say it like this, I now have to correct you. Instead, try wording it like this:

 

"Is it true that the SCAR-H's receiver is an inch longer, and wider, than a SCAR-L's?"

 

And don't just word vomit. If you're here to learn, it's at the grace of people who can answer your questions. Don't test their patience.

[Collimatrix]

 

15 hours ago, BarnOwlLover said:

I'm just explaining what I've been told by others elsewhere.  I'm ready and willing to learn as well.  However, if that's not desired here, I'm ready and willing to leave.

 

I've read the forum rules and requests, and I'm doing the best I can with what I know.  If that's not good enough, all you have to do say please go pound sand.

I haven't logged into your account and posted as you a long account of being sexually attracted to little boys and then banned you for it.  This would suggest that some of my anger issues have been mitigated by the regimen of powerful schedule III drugs I have been taking off-label for several months.  Congratulations on the successful outcome of this test.

The reason we're treating what you're saying as laughable and obvious nonsense is because it is.  It doesn't help that, when I very gently (by my standards) point out what's wrong with it, you just make shit up.

 

 

On 7/27/2020 at 5:52 PM, BarnOwlLover said:

The H has an upper that's nearly an inch longer than the L variant, let alone much wider. 

 

If the receiver on the H is wider, then how does this exist?  If the receiver on the H is wider then how come its bolt carrier isn't visibly wider?  

That especially doesn't make sense when you consider that the SCAR bolt carrier rides on rails that are an integral part of the receiver extrusion:

The SCAR-L and SCAR-H have exactly the same receiver cross section.  Originally, they were going to have a common receiver.  The program later relaxed the requirement for a unified receiver, which means that the uppers aren't identical.  They are, however, very close.

But you don't need to know details of the SCAR's program history to work out that the receivers probably have the same cross section.  You just need to use your goddamned head and think about it.

 

On 7/27/2020 at 5:52 PM, BarnOwlLover said:

Also, considering that most of the caliber conversions (such as 7.62x39) have focused on the H variant, I've wondered and come to think that the L is optimized around 5.56mm.  I actually can't remember there being any caliber conversions offered for the SCAR 16 aside from .300 Blackout. 

What.  Why would you think this.  Do you even think?

For one thing, caliber conversions for the SCAR-L for 7.62x39 do exist.

For another thing, this entire tangent of nonsense is internally inconsistent with the other nonsense you posted already.  If the HK 433 can accept larger calibers simply by having a magazine well that's a few pixels longer, then why does the FN SCAR require a receiver that's both wider and longer?

Like, think about this for just a fraction of a second.  Your entire train(wreck) of thought is just plain stupid.  This is what I was trying to hint at with the picture comparing the SCAR-L and SCAR-H, but this point went whistling harmlessly far, far above your head.

1)  The distance between the trunnion and the rear of the magazine well isn't what determines the maximum cartridge overall length a rifle can handle for several reasons.  The rifle needs enough distance from the inside of the rear of the magazine to the breech of the barrel plus distance to cam the locking mechanism into engagement and/or ramp the round up into alignment with the bore.  The breech of the barrel doesn't necessarily coincide with the trunnion.  Indeed, it could be argued that the FN SCAR doesn't really have a trunnion at all:

 

See?  There's no big internal buttress that the barrel attaches to.  It's held in from the side by screws.

2)  The thing you think is a trunnion isn't.  If you actually look at the patent, you can see that the thing you marked is the crosspin attachment for the lower portion of the handguard and the lower receiver.  It is not what holds the barrel on.

 

 

 

It happens to be near the barrel mounting hardware, but it does not hold the barrel on nor does it mark the breech of the barrel, which is several millimetres further back.

3) The lower receiver is clearly intended to take 5.56x45mm COAL rounds and magazines.  If they were intending to fire 7.62x51mm from that rifle... they would put a new lower receiver on it that can take the appropriate magazines.

4)  Again, I was gently hinting at this, but you missed it, the SCAR-H has a larger ejection port to accommodate the larger cases and a longer charging handle slot to accommodate the larger stroke of the bolt carrier.  If the 433 were designed with the option of longer calibers in mind, we would also see those features, but we don't so it isn't.


Actually think next time in order to prevent yourself from posting long and tiresome nonsense.

 

[Sturgeon]

Yeah, another thing to think about is that for arcane reasons I won't explain here, the total receiver length of a gas operated, rotary-locked rifle will be equivalent to 3*(C2-C1)+R1, where C1 is the cartridge overall length of the identical pattern smaller rifle, C2 is the new COAL, and R1 is the original receiver length. So, the HK433 being obviously designed for 5.56mm, you would need more extensive modifications (new upper + lower) to accommodate 7.62.

 

What is in contention is whether a 7.62 HK433 would need a new pin axis distance, or not. I could go either way on that.

[Miroslav]

Hey Sturgeon, you can't just drop an authoritative statement like that formula and not back it up. Please show us how you came to the number three. I'm genuinely curious. Having this extremely specialized hobby as well, I have a notepad at home with calculations made to the same end. Writing from on top of the loo at the office, I would have guessed at 2 rather than 3. Also, you must need a lot of premises to be valid for it to be true, mainly that the receiver was designed for optimization with regards to overall length.

 

There are a lot of CAD models of the scar availible online. Check out grabcad. I've got a model on my home pc that is quite accurate, and I think I got it from there. Way easier to measure than counting pixels.

 

Finally, while I enjoy the high level posting on this forum, I think you're being quite harsh on the OP. Who cares if it's the trunnion or the barrel extension.

[Collimatrix]

I haven't done the extensive modelling Sturgeon has, but, to a reasonable first approximation:

 

-Most new rifles these days are multi-lug, rotary bolt types

-There's a practical limit on how many lugs the bolt's locking area can be divided into

-There's a practical limit on how steep the cam track can be before the action of locking the bolt makes too much friction

-Therefore there is a practical limit on how much the length needed for the bolt carrier to lock and unlock the bolt can be minimized

[Sturgeon]

On 8/31/2020 at 4:17 AM, Miroslav said:

Hey Sturgeon, you can't just drop an authoritative statement like that formula and not back it up. Please show us how you came to the number three. I'm genuinely curious.

 

Well it's obvious that your receiver needs to be longer by 1 increment to accommodate the longer round. The second increment is the additional receiver length you need to accommodate the bolt which needs to not only be longer by that same 1 increment but also to travel behind the magazine enough to clear the rounds. So that's another increment. Your spring assembly and various other hardware also needs to be longer. Your bolt needs to be bigger and it will extend further too, so that's an additional bit of length, and you can approximate that as an extra increment. Together, that adds up to a 3x modifier. Take it from someone who's designed six rifles lol.
 

On 8/31/2020 at 4:17 AM, Miroslav said:

Also, you must need a lot of premises to be valid for it to be true, mainly that the receiver was designed for optimization with regards to overall length.

My formula clearly does not apply if you're pulling crazy BS. The Kel-Tec RDB does not follow this formula, for example. The F-7 doesn't follow this formula. They've both pulled tricks to cheat the length, which is ok! But most people aren't working on that level of detail so the rule applies in most circumstances.

I mean for example if your gun uses a vertically sliding breechblock and telescoped rammer assembly, then what I just said doesn't shake out. But if you're comparing an AR-15 to an AR-10, it does.

 

On 8/31/2020 at 4:17 AM, Miroslav said:

 

There are a lot of CAD models of the scar availible online. Check out grabcad. I've got a model on my home pc that is quite accurate, and I think I got it from there. Way easier to measure than counting pixels.

You know the F-4 was uploaded to GrabCAD for several months, right? I actually need to reupload it, since the ITAR rules changed.

[Miroslav]

On 9/4/2020 at 5:45 AM, Sturgeon said:

 

[...] Your spring assembly and various other hardware also needs to be longer. Your bolt needs to be bigger and it will extend further too, so that's an additional bit of length, and you can approximate that as an extra increment. Together, that adds up to a 3x modifier. Take it from someone who's designed six rifles lol.
[...]

I could buy the first two increments, but I don't think you should count having the spring in the forend as "crazy BS", and if it's in the forend (or there's just enough space in the carrier to stuff it in there anyway) you don't have to extend the receiver to fit the spring. Also you counted the bolt length twice. And you could have the hammer extend over the rear end of the magazine (or any bolt hold open device), which would save you from having to extend the firing pin all the way from the chamber to behind the rear of the magazine. I think the SU-16 has that configuration, but I'm not sure.

Yeah ok I'll quit the semantical nitpicking. I appreciate the attempt at generalizing. I wonder how well this stacks against the HK roller locked series, or a comparison of Garand/M14/Mini 14.

 

I've got some CAD models of long guns as well, but I'll keep them to myself for now. I have a PCC design that wouldn't require all that much of a workshop to put together, compared to a locked rotating bolt, gas operated rifle.

[Sturgeon]

 

57 minutes ago, Miroslav said:

I could buy the first two increments, but I don't think you should count having the spring in the forend as "crazy BS", and if it's in the forend (or there's just enough space in the carrier to stuff it in there anyway) you don't have to extend the receiver to fit the spring.

 

What I said was misleading, sorry. All of my rifle designs collapse the spring into the bolt carrier and there is no length behind the bolt at full rearward extension where the spring lives. 
 

58 minutes ago, Miroslav said:

Also you counted the bolt length twice.

No, I did not. Bolt assembly and bolt are not the same thing. I'm talking about two separate properties, that of the bolt carrier length needed and that of the bolt extension during unlocking.
 

1 hour ago, Miroslav said:

And you could have the hammer extend over the rear end of the magazine (or any bolt hold open device), which would save you from having to extend the firing pin all the way from the chamber to behind the rear of the magazine. I think the SU-16 has that configuration, but I'm not sure.

The F-5 does this. It still follows this rule.

 

1 hour ago, Miroslav said:

Yeah ok I'll quit the semantical nitpicking. I appreciate the attempt at generalizing. I wonder how well this stacks against the HK roller locked series, or a comparison of Garand/M14/Mini 14.

 

I think you just didn't understand what I was saying, which is largely my fault. I said a lot of things in a confusing way because I didn't pay enough attention to my composition when I made my reply.

 

[Sturgeon]

1 hour ago, Miroslav said:

I could buy the first two increments, but I don't think you should count having the spring in the forend as "crazy BS", and if it's in the forend (or there's just enough space in the carrier to stuff it in there anyway) you don't have to extend the receiver to fit the spring. Also you counted the bolt length twice. And you could have the hammer extend over the rear end of the magazine (or any bolt hold open device), which would save you from having to extend the firing pin all the way from the chamber to behind the rear of the magazine. I think the SU-16 has that configuration, but I'm not sure.

Yeah ok I'll quit the semantical nitpicking. I appreciate the attempt at generalizing. I wonder how well this stacks against the HK roller locked series, or a comparison of Garand/M14/Mini 14.

 

I've got some CAD models of long guns as well, but I'll keep them to myself for now. I have a PCC design that wouldn't require all that much of a workshop to put together, compared to a locked rotating bolt, gas operated rifle.

You can see how the F-5 takes great pains to telescope the hammer above the magazine:

[Sturgeon]

@Miroslav here's an example of what I'm talking about:



Archangel bolt group top, compared to Bearcat (new project) bottom. Note that because the magazine well is 0.4" shorter on Bearcat, that the BCG is 0.4" shorter, and that means an additional 0.4" less receiver is required behind the magazine well. Total length savings just accounting for those two items is therefore 2x 0.4" (0.8"). Other factors included would bring the total closer to 3x.

In Bearcat's case, total savings is likely to be closer to 2.5x, because there is no difference in bolt extension distance between it and Archangel. Under normal circumstances, there would be. Also I do not have a charging handle assembly that requires a slot in the receiver or anything like that, so there's unlikely to be savings there. But you can see how a difference in cartridge OAL actually compounds the difference in receiver length just by this example.

[Miroslav]

Well, as long as you have a set of premises to keep your definition of "normal circumstances", your formula holds up very well as a general pointer. I still think the factor "3" is high.

 

There are so many different kinds of tried and tested receiver shortening "crazy BS" design elements availible to a designer that perhaps the formula could be further specified to:

 

If: R2>3*(C2-C1)+R1

Then: designer is lazy

 

What do you mean by bolt extension distance? I'm guessing the difference in how far the bolt lugs protrude from the bolt carrier as the bolt is unlocked.

[Sturgeon]

7 hours ago, Miroslav said:

Well, as long as you have a set of premises to keep your definition of "normal circumstances", your formula holds up very well as a general pointer. I still think the factor "3" is high.

It is high but most engineers are not very good.
 

7 hours ago, Miroslav said:

 

There are so many different kinds of tried and tested receiver shortening "crazy BS" design elements availible to a designer that perhaps the formula could be further specified to:

Believe me, as the designer of the F-7 Shinden, I am no stranger to these.
 

7 hours ago, Miroslav said:

If: R2>3*(C2-C1)+R1

Then: designer is lazy

To a certain extent, yes! Or, he's very conservative, perhaps. But this is a formula for people who are not designing their own guns, but still want to make these sorts of assumptions.
 

7 hours ago, Miroslav said:

 

What do you mean by bolt extension distance? I'm guessing the difference in how far the bolt lugs protrude from the bolt carrier as the bolt is unlocked.

Distance between bolt locked and bolt unlocked positions.

For the record, I just finished the F-8 Bearcat, which is a shortened version of the F-12 Archangel, and the ratio it ended up with was 1.925:1. However, Bearcat is not a scaled down Archangel, but more of an "Archangel that ran headfirst into a wall". So it retains the same bolt extension, bolt thrust parameters, etc.

You can see them compared here: