Image credit
- Title
- File:Ithaca Auto & Burglar Gun.png
- Author
- U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives
- Licence
- Public domain
- Source
- https://commons.wikimedia.org/wiki/File:Ithaca_Auto_&_Burglar_Gun.png
How Muzzle energy is calculated
E = ½ · m · v²
Not calculated: m has no sourced figure yet. Nothing is substituted for a missing input.
No input on this calculation carries a clickable source yet.
How Muzzle velocity is calculated
no sourced velocity for this pairing
Not calculated: muzzle velocity has no sourced figure yet. Nothing is substituted for a missing input.
No input on this calculation carries a clickable source yet.
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
Not calculated: v_recoil has no sourced figure yet. Nothing is substituted for a missing input.
Assumptions
- Propellant gas momentum is excluded: ARMAG does not record charge weights (SPEC.md §14). 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.
1 of 2 inputs link to their source.
How Capacity is calculated
as published for the primary chambering
Inputs
- capacity2verifiedsourceTwo barrels, one round each. It has no magazine.
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
Not calculated: m has no sourced figure yet. Nothing is substituted for a missing input.
No input on this calculation carries a clickable source yet.
How Sectional density is calculated
SD = mass(gr) / (7000 · diameter(in)²)
Not calculated: mass has no sourced figure yet. Nothing is substituted for a missing input.
Assumptions
- Reported in the conventional lb/in² so it is directly comparable with published figures.
No input on this calculation carries a clickable source yet.
How Power factor is calculated
PF = mass(gr) · velocity(fps) / 1000
Not calculated: mass has no sourced figure yet. Nothing is substituted for a missing input.
Assumptions
- A competition classification defined by the IPSC and USPSA rulebooks, stated in their units. It describes a scoring category, not an effect.
No input on this calculation carries a clickable source yet.
How Magazine dump is calculated
t = (n − 1) / (rpm / 60)
Not calculated: rpm has no sourced figure yet. Nothing is substituted for a missing input.
Assumptions
- Cyclic rate held for the whole magazine, no stoppages, trigger held down. A theoretical figure for comparing mechanisms, not a measured one.
1 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.
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
- Shotgun
- Action
- Break action
- Fire modes
- Single shot
- Operating system
- Manually operated
- Feed
- not recorded
- Roles
- Designed in
- United States
- Produced in
- Introduced
- 1922
- Production
- 1922–1933
Dimensions and mass
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
- not recorded
- Trigger pull
- not recorded
- Effective range
- not recorded
- Units produced
The cited article gives "approx. 4,000" and names no source for it.
- Launch price
- not recorded
Chamberings
- 20 gaugeprimary2 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.
- Ithaca Auto & Burglar Gun406 mm15.98 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. Ithaca Auto & Burglar Gun records no height, so its outline is drawn at the type's proportion — that height is part of the shape, not a measurement.
Detail
A side-by-side double with the stock cut down to a pistol grip and the barrels to about a foot, sold between 1922 and 1933 to bank guards, payroll messengers and householders. Ithaca built roughly four thousand, and then the National Firearms Act of 1934 taxed short-barrelled shotguns out of the market and the product line ended.
It is here because it is the site’s only break-action arm, and a break action is worth seeing plainly: there is no magazine, no bolt and no mechanism to cycle. A lever unlocks the barrels, they hinge down on a pin, extractors lift the cases, and the whole firing sequence is two hammers and two triggers. Every other action on this site exists to automate what this one leaves to the hand.
At two kilograms firing 20-gauge shells it is also an object lesson in free recoil: there is very little mass to absorb the impulse and no stock to spread it against a shoulder.
The article publishes a 28-gauge chambering as well as the 20; no 28-gauge cartridge entry exists on this site yet, so only the 20 is recorded.
References
This entry's own bibliography. Every citation key on this page resolves into this list.
- Ithaca Auto & Burglar · Wikipedia · 1293391475 · read 2026-08-31 · CC BY-SA 4.0
Last verified 2026-08-31 · review status: agent-populated