actually, this chart is a bit more relevant as it assumes a muzzle velocity of 350fps with a .20
http://mackila.com/airsoft/atp/07-b-07.htm
That is pretty interesting, James. I've added the yellow line here...
...to highlight the results at 50 yards.
Nevermind the difference between 0.2's and the rest - we knew that, but the difference between 0.3's and 0.25's at only 1.14J surprises me - approx. 0.0625s / the maths is pretty simple - a person can sprint for short bursts at about 10m/s which means that...
@50yds in the time it takes for a shot to reach them a person can move 62.5cm further if the shot is a .25g BB compared to .3g
That's significant - it's just over the width of a man sized target!
That has me thinking I'm going to have to see how my own guns compare because, of course, the results are dependant on the hop set up performing well, ie lifting the BB without pressing on it so much that it reduces the velocity more than the benefits.
As a general rule however I would still say that if a gun gets less than 335FPS with 0.2's you're probably best sticking with 0.2's, especially if it is a stock gun. If you've upgraded the hop rubber, based on those^^ figures, it's got to be worth seeing how well it performs with 0.25's. I've tried 0.23's in Sabine, my tac AK, which has had a few different rubbers and, as is not surprising for me, I can't remember which was in her at the time - I didn't notice much difference: about 1.5-2m further effective range / now I am all about screwing as much range as possible out of my guns and i do, for eg, think it's worth trying to get as close to 350FPS as poss, so long as it's consistent, rather than accepting the 330-ish you get on average from an M100 spring, but you have to draw a line somewhere and i draw it at approx 5m improvement. I don't remember thinking the accuracy was better, but she's always been pretty good anyway, even right out of the box.
The clincher though is price - they're just not common enough for anyone to be buying in sufficient bulk in the UK for the price to come down. That said taiwangun.com (based in Poland so EU = no import tax) sell P&J 0.23g BB's & they're on -15% sale right now = €2.93 for 3000 I have only tried P&J 0.32's and they are ok, although I prefer Blaster Devils 0.3's for sniping accuracy / i did buy a bag of white 0.4's from ASPUK a while ago and i think they are P&J, but i can't remember for sure and i can't be arsed to go find them, but i haven't actually tried them yet anyway; as a rule of thumb though ASPUK don't sell shit. Taiwangun do bulk prices too so 25Kg on -8% sale is €138.55, but they also do free shipping on orders over approx €69 so you could get 72,000 for €70.16 all in. Dunno how long the sale will last - their discounts don't seem to be for set times, but it may be worth trying out 3000 and, if they're ok, maybe go halves with someone.
Blaster
are a good brand, but that doesn't mean that mistakes don't happen - you're right that your problems sound like it must be the shape. The tip about not stuffing midcaps completely full is a good one in my experience, but something you said above is also important - that when you get a jam it sounds like dry firing. That tells us there is no BB in the hop unit, or it would sound duller. For some reason they are not feeding. What I think whomever you spoke to was trying to explain about strong tappet plate springs causing misfeeds is that, with high rates of fire, the air nozzle can spring back into place before the next BB has been able to pop up ready to be pushed into the barrel. The way to prevent this is what is called a tappet plate delayer, or 'delayer chip', which is a little circle of brass or piece of plastic which clamps onto the peg on the sector gear to keep the tappet plate in its withdrawn position for a few milliseconds longer. The thing is that the weight of the BB should make no difference to this effect and whether they are coming out of a hicap or midcap shouldn't make much difference either (although there is a small difference in the strength of spring pressure pushing the BB's up).