Image credit
- Title
- File:HK33A2 Flickr (yet another finn).jpg
- Author
- yet_another_finn / Mika Järvinen(attribution required)
- Licence
- CC BY 2.0
- Source
- https://commons.wikimedia.org/wiki/File:HK33A2_Flickr_(yet_another_finn).jpg
.jpg){kind=link}
How Muzzle energy is calculated
E = ½ · m · v²
Inputs
- m4.018 g62.01 grverifiedsource62 gr as published, converted to grams.
- v911.5 m/s2,990 fpsestimatedInterpolated between sourced measurements at 368.3 mm and 508 mm.
1 of 2 inputs link to their source.
How Muzzle velocity is calculated
linear interpolation between the two nearest sourced barrel lengths
Inputs
- v at 368.3 mm905.3 m/s2,970 fpsverifiedsourceTable 2-1, muzzle velocity for the M4: 2,970 fps.
- v at 508 mm944.9 m/s3,100 fpsverifiedsourceTable 2-1, muzzle velocity for the M16A2: 3,100 fps. The M855 is the manual's service round for that rifle.
Assumptions
- Velocity is assumed to vary linearly between the two measurements. Over a short span that is a reasonable reading of the data; it is not a law.
2 of 2 inputs link to their source.
How Loaded mass is calculated
m_loaded = m_empty + m_magazine + n · m_cartridge
Not calculated: m_magazine has no sourced figure yet. Nothing is substituted for a missing input.
Assumptions
- One magazine, filled to the stated capacity. Spare magazines, optics, slings and lights are the owner’s, not the arm’s.
2 of 4 inputs link to their source.
How Free recoil is calculated
E_recoil = ½ · m_firearm · v_recoil²
Inputs
- m_firearm3.65 kg8.047 lbestimatedHK33A2, from the infobox. Wikipedia cites this figure to a Small Arms Review 'HK33 Brochure' page that now 404s and could not be independently read, so it is recorded as estimated rather than verified.
- v_recoil1.003 m/s3.292 fpsestimated
Assumptions
- Propellant gas momentum is excluded: ARMAG does not record charge weights. This is therefore a lower bound on the real free recoil, consistent between entries but smaller than a figure that includes the gas term.
- Free recoil: the arm is unrestrained. Stock design, muzzle devices, stance and shooter mass are not modelled, because none of them is a property of the arm.
No input on this calculation carries a clickable source yet.
How Capacity is calculated
as published for the primary chambering
Inputs
- capacity30estimatedsourcepublished as 25, 30 or 40-round detachable box magazines, from the infobox, uncited there; 30 rounds recorded here as the most common capacity.
1 of 1 inputs link to their source.
Derived figures
Computed from the sourced values above. Open ƒ on any figure for the formula, its inputs, and the assumptions it makes.
How Momentum is calculated
p = m · v
Inputs
- m4.018 g62.01 grverifiedsource62 gr as published, converted to grams.
- v911.5 m/s2,990 fpsestimatedInterpolated between sourced measurements at 368.3 mm and 508 mm.
1 of 2 inputs link to their source.
How Sectional density is calculated
SD = mass(gr) / (7000 · diameter(in)²)
Inputs
- mass4.018 g62.01 grverifiedsource62 gr as published, converted to grams.
- diameter5.7 mm0.2244 inestimatedsourceNo free NATO dimensional standard is published. The C.I.P. datasheet for the .223 Remington, which shares this bullet, gives a cartridge-maximum bullet diameter of 5.70 mm.
Assumptions
- Reported in the conventional lb/in² so it is directly comparable with published figures.
2 of 2 inputs link to their source.
How Power factor is calculated
PF = mass(gr) · velocity(fps) / 1000
Inputs
- mass4.018 g62.01 grverifiedsource62 gr as published, converted to grams.
- velocity911.5 m/s2,990 fpsestimatedInterpolated between sourced measurements at 368.3 mm and 508 mm.
Assumptions
- A competition classification defined by the IPSC and USPSA rulebooks, stated in their units. It describes a scoring category, not an effect.
1 of 2 inputs link to their source.
How Magazine dump is calculated
t = (n − 1) / (rpm / 60)
Inputs
- n30estimatedsourcepublished as 25, 30 or 40-round detachable box magazines, from the infobox, uncited there; 30 rounds recorded here as the most common capacity.
- rpm750 rpmestimatedsourceHK33A2, from the infobox, uncited there.
Assumptions
- Cyclic rate held for the whole magazine, no stoppages, trigger held down. A theoretical figure for comparing mechanisms, not a measured one.
2 of 2 inputs link to their source.
How Sight error at 1 mm is calculated
θ = atan(misalignment / sight radius)
Not calculated: sight radius has no sourced figure yet. Nothing is substituted for a missing input.
Assumptions
- Shows what a stated aiming error costs. The misalignment is the reader’s figure; the site does not claim how well anyone aims.
No input on this calculation carries a clickable source yet.
Variants
HK33A3
The retractable-stock version of the HK33A2, keeping the same roller-delayed blowback action, barrel and cartridge but replacing the fixed stock with a telescoping one.
- Mass, empty
from the infobox, uncited there.
- Length
stock extended, from the infobox, uncited there.
- Length, folded
stock collapsed, from the infobox, uncited there.
HK33KA3
A short-barrelled carbine variant of the HK33A3 with a retractable stock, keeping the same action and cartridge on a shorter barrel.
- Mass, empty
from the infobox, uncited there.
- Length
stock extended, from the infobox, uncited there.
- Length, folded
stock collapsed, from the infobox, uncited there.
- Barrel length
from the infobox, uncited there.
HK53
The shortest-barrelled member of the HK33 family, a compact carbine with a retractable stock that kept the roller-delayed blowback action and 5.56mm chambering of its longer siblings.
- Mass, empty
from the infobox, uncited there.
- Length
stock extended, from the infobox, uncited there.
- Length, folded
stock collapsed, from the infobox, uncited there.
- Barrel length
from the infobox, uncited there.
- Cyclic rate
from the infobox, uncited there.
| Variant | Years | Changes |
|---|---|---|
| HK33A3 | — | Mass, empty, Length, Length, folded |
| HK33KA3 | — | Mass, empty, Length, Length, folded, Barrel length |
| HK53 | — | Mass, empty, Length, Length, folded, Barrel length, Cyclic rate |
Specifications
Every row here is generated from the schema, so a figure recorded on this entry cannot be missing from the table, and the same rows, read the same way, are what the comparison shows.
Identity
- Type
- Rifle
- Action
- Self-loading
- Fire modes
- Semi-automatic
- Fully automatic
- Operating system
- Blowback, roller-delayed
- Roles
- Designed in
- Germany
- Produced in
- Introduced
- 1968
- Production
- not recorded
Dimensions and mass
- Mass, empty
- 3.65 kg8.047 lbestimated
HK33A2, from the infobox. Wikipedia cites this figure to a Small Arms Review 'HK33 Brochure' page that now 404s and could not be independently read, so it is recorded as estimated rather than verified.
- Magazine, empty
- not recorded
- Length
HK33A2, stock extended, from the infobox; no inline citation is given there.
- Length, folded
- not recorded
- Width
- not recorded
- Height
- not recorded
- Barrel length
HK33A2, from the infobox; no inline citation is given there.
Sights and rifling
- Sight radius
- not recorded
- Sight height over bore
- not recorded
- Rifling twist
- not recorded
- Twist direction
- not recorded
- Grooves
- not recorded
- Sight graduation
- not recorded
Operation
- Cyclic rate
HK33A2, from the infobox, uncited there.
- Trigger pull
- not recorded
- Effective range
- not recorded
- Units produced
- not recorded
- Launch price
- not recorded
Chamberings
- 5.56x45mm NATOprimary30 rounds
- .223 Remington30 rounds
Scale
A to-scale outline against family siblings. The dimensions are sourced; the shape is a representative outline for the type, and says so.
- Heckler & Koch HK33920 mm36.22 inheight not recorded
Representative outline: the dimensions are sourced, the shape is not. Overall length, and barrel length where recorded, are drawn from this entry's own figures; the profile is a generic one for the firearm type and says nothing about this arm's actual contours. Heckler & Koch HK33 records no height, so its outline is drawn at the type's proportion. That height is part of the shape, not a measurement.
Gallery
Image credit
- Title
- File:Chilean Marine HK33.jpg
- Author
- Unknown author Unknown author
- Licence
- Public domain
- Source
- https://commons.wikimedia.org/wiki/File:Chilean_Marine_HK33.jpg
Image credit
- Title
- File:Turkish HK33.JPG
- Author
- MoserB
- Licence
- Public domain
- Source
- https://commons.wikimedia.org/wiki/File:Turkish_HK33.JPG
Detail
Heckler & Koch developed the HK33 in the 1960s primarily to sell abroad, applying the roller-delayed blowback mechanism of its G3 battle rifle to a lighter rifle built around the smaller 5.56mm cartridge rather than 7.62×51mm NATO. Downscaling the mechanism was not a simple resizing: the geometry that governs how the rollers transmit force between the bolt head and the bolt carrier had to be reworked for the lower-pressure, lighter case, since the ratios that let the G3’s action delay unlocking correctly do not scale linearly with cartridge size. The result kept the G3 family’s stamped-steel receiver and lack of a gas system, an arrangement that depends entirely on case friction, bolt mass and spring pressure to hold the action closed long enough for pressure to drop to a safe level.
Despite reaching a wide range of export customers and remaining in production for decades, the HK33 never matched the commercial reach of the 7.62mm G3 it was derived from. Heckler & Koch built it in several configurations from the same basic mechanism: the fixed-stock HK33A2, the retractable-stock HK33A3, the carbine-length HK33KA3, and the still shorter HK53, which trades reach for a compact package. All four share this entry’s action and operating system and differ only in stock and barrel length, so they are recorded here as variants rather than separate entries.
Most figures in this entry come from the Wikipedia infobox without an inline citation and are recorded as
estimated; the one figure that is cited there points to a Small Arms Review page that no longer resolves
and could not be read directly, so it too is recorded as estimated rather than verified. No published
muzzle velocity carries a barrel length that matches this entry’s barrelLength field, so none is recorded,
and no twist rate is published for the rifle.
References
This entry's own bibliography. Every citation key on this page resolves into this list.
- Heckler & Koch HK33 · Wikipedia · 1373795397 · read 2026-09-09 · CC BY-SA 4.0
Last verified 2026-09-09 · review status: agent-populated