Nope, no issues related to projectile speed.
Maybe i didnt make my point clear.
Projectile speed matters only at range - if you are closer to the asteroid, to have more efficient limpet travel time, projectile speed is not that important.
To hit a deposit from 300m is easy enough. To hit it from 1km, it not that easy - but it makes limpet travel too long that there is no point to even shoot it at 1km
So doubling the speed means i can hit a deposit at 600m as reliably i could hit at 300m - but why would i do that? I need my limpets to collect that fragment faster and shooting it at 600m does not help with that.
And not at last: the abrasion blaster is not ammo dependent. So achieving a fragment on first hit is not that important when you can simply spam the blaster.
So yea, i dont see the speedier abrasion blaster a must. Not even something really useful. Vaguely useful at best.
On the other hand, a sub-surface missile or a core missile with double the speed - that would be nice, but even nicer would be high-capacity mining missiles...
Heck - they should simply enable engineering on mining stuff...