IMHO, you've just discovered the single biggest issue with the Tikka Tactical rifle, at least in the .223 chambering -- a ridiculously short magazine length for a rifle that has a 1-8" twist. The barrel is all set up for heavy bullets, but the mag sure isn't.
And yes, just for good measure, the throat is on the long side -- at least that's how mine is.
Truly, I just don't get why Tikka has never rectified the situation by coming out with a magazine set up for a longer cartridge OAL, which would allow the rifle to due what it's presumably supposed to do. It makes me want to scream every time I look at the mag, as there's all that space, but it's blocked with a panel of injection molded plastic (and if you cut it out, then the follower isn't long enough). Grr!!!!