setting aside the wisdom of “signing” one’s kills, how effective would a rifle chambered for a unique custom round be as a signature?
clarifying, i don’t mean like a special payload or anything like that. i mean like a rifle chambered for a bottlenecked 10x80mm cartridgethequantumqueer
The issue is, you’re making a custom round for a custom built weapon. Because there is no existing cartridge, you’d need to make almost all of this from scratch. And, you’re doing all of this to create an (almost certainly) inferior analog to a CheyTac Intervention chambered in .408 (10.36x77mm.)
A 10×80 cartridge would be one of those hybrid sniper/anti-materiel rounds, along with rounds like the .338 Lapua, the .416 Barret, and at least a half dozen other relatively modern rounds. Designed in an attempt to bridge between 7.62mm NATO and .50BMG, a lot of these have been designed in the last 20 years. These are used at extreme ranges (around a mile).
This means your character, or their gunsmith, needs to be able to flawlessly design and fabricate the entire weapon from raw materials. Now, that’s not, technically, impossible, but it’s the next best thing. Converting an existing rifle to a custom cartridge is possible, but would also be extremely difficult. This is after you remember that messing around with any of these rifles requires a skilled gunsmith.
Doing full R&D to create a rifle like that from scratch would cost millions of dollars, and might be equal to an off-the-shelf L115A3. Also, bonus points in that, while the L115A3 isn’t civilian purchasable, .338 Lapua has made it onto the civilian market, so your character could get ammunition for their rifle without difficulty.
So, let’s step back from the 10x80mm for a second. If your character is using a milspec rifle chambered in one of these rounds, it’s very likely they’d be handloading their own cartridges. This can result in better performance than a mass produced shell, and gives the shooter the ability to fine tune a lot of factors in how their rifle will perform. In cases like this, the handloaded round will outperform off-the-shelf cartridges.
There are a lot of custom guns out there. In particular, some manufacturers offer high end custom pieces, so it’s possible you might see a one-of-a-kind rifle, usually modified off of a venerable pattern. Though at that point, it’d be extremely unlikely it’d be chambered in an experimental cartridge.
Realistically, there’s three combat applications for this kind of a round. Your character is a sniper, at which point, there are better, significantly cheaper, options. Your character is a government-backed assassin, at which point having any signature is a horrible idea, as it makes it easier to tie their actions together. Your character is a criminal assassin. I know we’ve talked about the problem for a hitman reusing the same gun, but, “there’s only one person out there who uses a 10mm rifle round,” is far worse. Though, to be fair, it’s not as dumb as someone blithely saying, “there’s only one man that uses a Walther PPK.” Fox Mulder? No, Robert McCall? No, wait, I’ll get this one eventually.