The Angstrum is a heavy sidearm of  Corpus design that fires powerful micro-rockets. Its charge-based trigger allows for firing precise single shots, or emptying the entire magazine as a spread barrage for engaging single heavy targets or large groups.

Update 32.0 (2022-09-07)

Ammo Changes
We understand the power fantasy of these weapons is very popular for some, so our first approach was to keep them powerful, but limit how often they can be used by making changes to ammo pick-up.
Ammo Pickup Overrides
The following weapons now have ammo pickup overrides, meaning they gain less from picking up ammo. This mostly applies to AoE weapons, in hopes that players will become more deliberate with their aim to make the most of their Ammo pools. The following lists the specific ammo pick up overrides per weapon category.
Secondary Weapon Ammo Pick Up Overrides
3 Ammo per Pick Up: 

Angstrum
Headshot Damage Changes
During playtesting, the ammo changes alone weren’t enough to significantly change things for AoE weapons. So instead of tightening these values to be overly restrictive, we chose to address other factors that make these weapons so strong, such as headshot damage. 
Our approach here is two-fold, to reduce the impact of headshots for AOE weapons, but to also make precision headshots pack a larger punch overall.

Radial damage no longer gains extra headshot damage or triggers headshot conditions.
This is primarily targeted at the Ignis Wraith - as a “flamethrower” weapon, it’s hard to imagine a blanket of elements being precise enough to target weak points specifically. Explosive projectiles themselves can still land headshots, so there is still a reason to aim with most weapons for maximum damage.
Hotfix 27.2.2 (2020-03-06)
Reduced the following AoE weapons Radial Damage Falloff from central impact that were all previously 90%:

Angstrum: 40%
Update 27.2 (2020-03-05)

Self Damage Changes

We are getting rid of Self Damage and replacing it with something else: instead of Self Damage, it’s now ‘Stagger’. This change completely removes the chance of killing yourself, and instead now creates scenarios where you will interrupt yourself - or ‘Stagger’ - to varying degrees if you aren’t careful. 
The degrees of Self-Interrupt start with a small stumble all the way to full knockdown depending on how close you are to the center of explosion. Any Mods referring to Self Damage will be converted to acknowledge Stagger.
With this Self-Interrupt system, we have added dozens of new recovery animations that harness a ninja-like recovery experience. By pressing ‘Jump’ at the correct time, you can execute a ninja-skill-based knockdown recovery to ALL in-game knockdowns. This ninja recovery window is indicated by a glowing FX on your Warframe.
In the original Dev Workshop, we said:
As a result of this overall systemic change, Weapons with Stagger will be getting approximately a 20% buff in Damage, with any weapons with AOE receiving a 50% Radial Damage Falloff from central impact.
This is no longer accurate after continued testing. What we are doing now is:
No damage buffs have been added, but any weapons with AOE are receiving ~20% increase in Radius. Additionally, AOE weapons are receiving a 90% Radial Damage Falloff from central impact. This means on the very outer section of the explosion Radius 10% of the Damage will be dealt. Tactics will be deadly - aim true, Tenno. 
Why: Several players brought up the history of the Tonkor and we want to make sure we ship this change in a place that’s conservative in its starting point from a balance perspective. The complete removal of Self Damage does change the pace of destruction with some of the game’s most powerful weapons, so we want to make sure we can iterate upwardly instead of releasing a bonanza of explosions with no other choices.

Greater than 100% Status having meaning

Shotguns have a unique Role here based on a very patch-work history with how they interact with Status Chance. A Shotgun that shoots 99% Status Chance would give you 35% (roughly) status per pellet. 100% Status Gives you 100% Status per pellet. This huge jump in performance happens with just a 1% gain - why? Well, to answer that we have to look at our choice to make what the UI conveys reality. It would feel broken to shoot a Shotgun with 100% Status and not see a perfect spread of Effects. In reality, to make Status consistent we have to treat Shotguns as a special case. 
Shotguns as a special case means we have buffed the Status Chance of all Shotguns by x3 or greater. The UI now behaves to show the reality that you are determining Status Chance per pellet.
Hotfix 23.0.3 (2018-06-19)

Fixed Angstrum not having any shooting sounds.
Update 22.12 (2018-02-09)

Direct Impact damage increased from 175 to 200.
Status chance increased from 10 to 22%.
Critical chance increased from 5% to 16%.
Ammo capacity decreased from 30 to 18.
Update 22.0 (2017-10-12)

Improved the mesh quality of the Angstrum to avoid blocky textures.
Fixed Clients not seeing the Host's Angstrum ammo magazine cycle correctly.
Update 21.6 (2017-08-29)

Improved the Angstrum's explosion FX.
Update 21.0 (2017-06-29)

Fixed the Angstrum generating infinite spread for its first shot.
Fixed Angstrum's charge animation not loading bullets into the weapon chamber.
Update 20.0 (2017-03-24)

Fixed a visual bug for Clients where the charged shots of the Angstrum would appear to fire twice.
Update: The Silver Grove (2016-08-19)

Angstrum damage and projectile speed increased in Conclave.
Update: Lunaro (2016-06-15)

Fixed hearing fully charged sounds when firing the Angstrums last shot.
Hotfix 18.6.2 (2016-03-22)

Fixed the Angstrum not playing the proper audio FX when charging up.
Update 18.6 (2016-03-16)

Fixed Angstrum displaying incorrect noise level in the Arsenal.
Update 18.5 (2016-03-04)

Angstrum Conclave skin now available.
Increased the damage of the Angstrum in Conclave.
Hotfix 18.4.10 (2016-02-11)

Removed the headshot multiplier from the Angstrum in Conclave.
Increased the Angstrum's initial projectile speed in Conclave.
Reduced the Angstrum's ammo pool in Conclave.
The Angstrum's explosive damage no longer ignores cover in Conclave.
Update 17.9 (2015-10-28)

Angstrum Day of the Dead Skin is now available.
Update 17.5 (2015-10-01)

Angstrum damage increased in PvP.
The Angstrum has received the PBR treatment!
Update 16.11 (2015-07-07)

Fixed the Angstrum always showing as having 0 magazine capacity.
Update 16.4 (2015-04-23)

The Angstrum has been balanced for use in PvP.
Update 14.2 (2014-08-13)

Base ammo increased to 30 (from proposed 21) considering the volume of projectiles launched.
Hotfix 14.0.5 (2014-07-21)

Performance Improvements for Mirage + Hall of Mirrors and Angstrum.
Hotfix 13.3.1 (2014-05-15)

Fixed multishot mods not allowing for random chance of extra rocket when applied to Angstrum.
Update 13.3 (2014-05-14)

Introduced.