I THINK this is a .338 Lapua Magnum.
Our Specops have been using this caliber for years.
You’re right, it’s a .338 Lapua Magnum. The Brits seem to like using the 250 grain projectiles. I prefer the heavier 300 grain rounds in mine. The .338 LM is a round that will tear you another pooper at 2000 without even trying.
If you want one that is more accurate and cleaner than the AI gun, talk to Mike Rock at Rock Creek Barrels. He can set you up one on the M24R platform he builds for around $3k and it’ll be a tack driver.
Mike