04-Aug-2026
Type “can a Beretta A400 shoot 3.5 and 3 inch shells” into Google, and you’ll find pages of forum argument and very few straight answers. It’s one of the most common questions among UK shotgun owners, and it matters; putting the wrong cartridge through the wrong chamber is at best expensive and at worst dangerous. The good news is that the rules are simple once you understand what chamber length actually means, where to find it stamped on your barrels, and how proof marks fit into the picture.
This guide walks through chamber lengths, cartridge markings and compatibility for UK shooters, whether you’re running a modern semi-auto like the Beretta A400 or a fifty-year-old English side-by-side.
What chamber length actually means
The chamber is the section at the breech end of the barrel that houses the cartridge when you close the gun. Its length is measured to fit the fired, that is, unfolded, length of the cartridge case, not the crimped length of the unfired shell. This trips up a lot of shooters: a “70mm” cartridge looks much shorter than 70mm in your hand because the crimp is folded shut. When the shot leaves, the crimp opens fully, and that opened case must fit inside the chamber.
Common chamber lengths you’ll see in the UK are 65mm (2½in), typically on older English game guns; 70mm (2¾in), the long-standing standard for many sporting guns; 76mm (3in), often called magnum and now common on modern game and wildfowling guns; and 89mm (3½in), the super magnum found on dedicated wildfowling semi-autos.
The golden rule: Shorter is fine, longer is not
The core compatibility rule is straightforward. You can safely fire a cartridge that is shorter than your chamber, but you must never fire one that is longer. A 70mm shell in a 76mm chamber is perfectly normal practice. A 76mm shell in a 70mm chamber is not, the opened crimp intrudes into the forcing cone, pressures spike beyond what the gun was proofed for, and you risk serious damage to the gun and yourself.
So to answer the question directly: a shotgun chambered at 89mm (3½in) will generally also cycle and fire 76mm (3in) and 70mm (2¾in) loads, subject to the maker’s guidance, this is exactly why wildfowlers like 3½in-chambered semi-autos such as the A400 Xtreme variants. A gun chambered at 76mm can shoot 76mm and shorter, but never 89mm. Always confirm your own gun’s chamber marking rather than assuming by model name, because many models are offered in more than one chamber specification across their production life. Semi-autos add one wrinkle: very light short loads may not always cycle the action reliably in a gun set up for heavy shells, which is a function issue rather than a safety one.
Where to find your gun’s markings
Every legitimate shotgun sold in the UK carries proof marks, usually on the barrel flats or breech end of the barrels. Among them you’ll find the chamber length, marked either in millimetres (65, 70, 76, 89) or inches, alongside the gauge and the proof pressure. If your gun was proofed abroad, Italian guns through the Gardone proof house, for example, the marks look different but carry the same information. If you can’t read or find the markings, or the barrels have been altered, have a gunsmith or Registered Firearms Dealer check the gun before shooting it. It takes minutes and removes all doubt. Our guide to choosing the right cartridge covers what the numbers on the cartridge box mean in more detail.
Steel shot and proof: The modern complication
Chamber length is only half the compatibility story now that steel shot has become mainstream. Standard steel loads can be used in most nitro-proofed guns within certain limits, but high-performance steel cartridges require the gun to carry specific high-performance steel proof, shown by a fleur-de-lys mark on guns proofed to the relevant standard. Driving hard steel loads through a tightly choked older gun that was never proofed for them is a recipe for barrel damage. With the transition away from lead gathering pace across UK shooting, it’s worth reading the cartridge box carefully: manufacturers state clearly whether a load is standard or high performance, and what proof and choke it requires. Our piece on the best shotgun cartridges for clay shooting looks at how these choices play out on the clay ground.
Older guns and 65mm chambers
Thousands of beautiful English game guns in circulation have 65mm (2½in) chambers, and they remain superb tools, provided they’re fed correctly. Several UK cartridge makers load excellent dedicated 65mm game cartridges, so there’s no need to retire an older gun, and no excuse for slipping 70mm shells into it because they “seem to fit”. They will fit in the chamber unfired; that’s precisely the danger. If you’re browsing second-hand shotguns at the older end of the market, factor chamber length into your decision the same way you’d factor in choke, stock length and condition.
FAQ
Can a Beretta A400 shoot both 3½in and 3in shells? It depends which A400 you have. Versions chambered at 3½in (89mm), check the barrel marking, will generally handle 3½in, 3in and 2¾in loads, per Beretta’s guidance. Versions chambered at 3in must not fire 3½in shells under any circumstances. The barrel stamp, not the model name, is the authority.
Can I shoot 2¾in cartridges in a 3in chamber? Yes. Firing cartridges shorter than the chamber is safe and completely normal. The only caveat is that some semi-autos may not cycle very light loads reliably.
What happens if I fire a cartridge that’s too long for my chamber? The case mouth opens into the forcing cone, constricting the shot’s exit and driving pressure well beyond proof levels. Consequences range from bulged barrels to catastrophic failure. If you suspect it has happened, stop shooting and have the gun inspected.
How do I know if my gun can shoot steel shot? Standard steel is acceptable in most nitro-proofed guns within CIP guidelines and with appropriate open chokes. High-performance steel requires dedicated steel-shot proof, indicated by the fleur-de-lys marking. If in doubt, ask a gunsmith to check the proof marks.
Find your next shotgun on Rightgun.uk
Whether you’re after a 3½in-chambered wildfowling semi-auto, a 76mm game gun or a classic 65mm English side-by-side, you’ll find new and used listings from sellers across the country on Rightgun.uk. Browse the full range of shotguns for sale, compare chamber specs and condition, and buy with confidence on the UK’s dedicated shooting marketplace.
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