The 5.45 round has been around in Soviet service starting in 1974.
there was not a single round of the ammo in the west until about 1985 when SOF magazine was able to get a case from Afghanistan.
Even then it was not widely known in the west to civilian shooters. I remember seeing the ammo at Knob Creek about 8 years ago for $5 a round.
At first the East german sniper rifles came in, but they were not popular, then the Ronanian SAR,CUR, etc series started to come in. Once shooters started to take notice the round really had cought on, but it is still not as popular because it is so new.
Supply has always been somewhat of a minor problem. With Romania being the majot supplier of rifles, there are only so many out there. Also many just see no need for another AK in other round when their 7.62 X 39 does them just fine.
The round will never really catch on until a domestic rifle manufacturer producs a rifle in the caliber. Ammo will follow, and other companies will jump on board.
The other problems are that the commie ammo is so cheap the American companies just can not produce it for a price that can compete. Given time they might start producing the caliber, but remember Winchester has only just re-introduced 7.62 X 54R, and has started 9 X 18, and 7.62 X 25 in a weak loading.
The tried and true .223 is well established, and the round will have to show some competition to this round in a varmit rig before I think it will catch on. Would I buy a Remington 700BDL heavy barrel varmet rifle in this caliber if it were loaded with Match Kings or the like... hell yes. Until enough others people would buy this too, we must use our AKs.
just my two cents.