Are my bullets disintegrating in flight?

A 14 twist would be fine for a 52 grain bullet, the OP's rifle is generating twice the RPMs. It is definitely "stable", just overstressed.

26.7 grains of Ramshot TAC is over Max for a 52 grain bullet. By 2 full grains for one Western Powder listed load. 1.7 according to the other load. Max velocities at listed Max loads are a tick over 3200 fps out of a 1 in 12, 24" barrel. One or two over will very likely not get to 4,000 fps out of a 16", 1 in 7 barrel .
Still doubt the bullet is disintegrating though. A Match ELD isn't designed to expand upon impact. More likely the wee bullet are being stabilized in the wee short barrel and the bullets are flying elsewhere. Suggest you put up a big sheet of paper(Butcher paper preferably) behind the target and see.

Have somebody watch. If your bullets are disintegrating, they should see what looks like a streak of smoke as the bullet comes apart.

Just a thought, do you have a muzzle brake or anything attached to the barrel? Might make sure it is nice and tight and doesn't show any evidence of the bullet brushing it as it exits.

When thin skin bullets fly a part that's too much RPM. Velocity x twist = rpm. You need to slow down one or the other or both.