Gamebore have a 2 1/2 inch steel load. Have put their spiel below. but like Marakai says, getting it in oz slim to none. https://gamebore.com/cartridge/game/12g-Regal-Steel-Bio-Wad

Gamebore’s soft steel is produced to CIP regulations by one of the world's leading manufacturers for consistency in its sphericity and size to deliver outstanding patterns.

Suitable for all guns with 1954 and onwards proof marks, for use with half choke or less. Standard Steel ammunition can be used in any shotgun (other than Damascus/twist barrelled guns), in good order bearing London or Birmingham proof symbols from 1954 onwards. For pre-1954 shotguns guidance will be needed from the British Proof Authority. The shotgun must be chambered for the case length of the ammunition as a minimum. Longer chamber lengths can be used with shorter ammunition.

All cartridges should be stored at room temperature in a dry location. Adverse temperatures may affect performance. Do not expose to extreme temperatures.

Specialist Cleaning Instructions: Using a bronze wire brush, remove the excess wad residue whilst dry. Next, spray a mild, water-based household cleaning product such as glass cleaner down the barrels and leave for a few minutes to allow the breakdown of any stubborn residue. Use the bronze wire brush again to remove any remaining streaks, followed by a rag or dry tissue to wipe away the remaining cleaning product. Dry the barrels thoroughly before applying a gun oil.

As with any type of cartridge; barrels and chokes should be cleaned after each use to avoid buildup of residue