hi Tom,
I remember when I first started using a pump it took me ages to get the reservoir filled and debubbled. Now it just takes a minute or so and I don't have problems some of it I'm sure is just confidence. I use a minmed, an older model to yours and the smaller reservoir but I would have thought it was the same. I'm tried to write down what I do. I'm not claiming it's the right way to do it but it works for me.
(it may not be any different to what you do so sorry if its nothing new but nothing ventured...)
1) use insulin at room temperature.
2) Before filling pull the plunger up and down a couple of times, this distributes the lubricant, and helps prevent air entering past the O rings.) twist to the right a bit.
3) withdraw plunger to 180u (in your case it would be 300u)
4) place on vial (vial upright) push in air.
5) Invert vial, it will partially fill from pressure. Pull back plunger gently but firmly to fill (maybe 3/4 full, then gently push a little of it back through the insulin(their shouldn't be much air at all but this is where I used to start having problems, if air has entered through the O rings and you keep doing this, the insulin will become more and more bubbly)
6) repeat if necessary ...hardly ever is now, then pull back to the 180u (300u) flick and hold to the light to see if there are any bubbles, If there are push out the top bit of insulin and bubble and then completely fill again.Hopefully by now there are no bubbles.
8) remove plunger and insert into (rewound) pump.
7) When I purge the tubing I make sure that the pump is upright so if there are any remaining bubbles they are at the top.