Used rechargeables in Ion's, Mini, PMR2010, PM8 and rotors. All worked fine.
However did have some issues with some nasty unkown brand 9V crap off ebay (avoid like plague, claim to have 300mAh and shop says its in Australia but goods come from China). One blew up on charger and other died in marker (top came off). Moral of the story - use good branded stuff and you should be ok.
I am using Ansman MaxE 250mAh. Choose the MaxE as these have a very slow discharge compared to normal higher rated mAh batteries. Also have a uniross 200mAh Hybrio battery (again slow discharge). Using Extreme 2200 mAh AA's which are also of the slow discharge type.
Did some research (google is indeeed your friend) and discovered that the slow discharge type of batteries have a much lower internal resistance than other rechargeable batteries making them very good for high demand items such as digital SLR's and therefore paintball markers. As such, a battery with a high mAh will not necessarily outlast one with a lower mAh it depends on a number of other factors.
For those interested in looking in more detail the sites I looked at are below:
http://www.rechargeable-battery-review.com/consumer-batteries/aa-battery-tests/aa-rechargeable-batteries-reviews-master-list.html
http://http://www.batteryreview.co.uk/how_we_test_batteries.htm
http://www.stefanv.com/electronics/sanyo_eneloop.html
Site illustrating the low internal resistance :
http://http://www.wheelchairdriver.com/rechargable-AA-battery-testing.htm
One thing that is true is that rechargeable batteries have a lower voltage rating than your normal alkaline batteries. In terms of the PP3 batteires, the alkalines start out at 9V but start to drop as they are used. Due to the way the voltage drops this is a good indicator of how much life is left in your battery. When fitted to your marker these will give an accurate indication as to how much life you have left and as such can warn you that you really ought to change batteries soon.
Unfortunately rechargeable batteries work differently. They start at a lower voltage and as such a fully charged one may not indicate it is fully charged in your marker (but all the ones I have tried did). The big problem is that the rechargeable battery holds its voltage relatively stable and then suddenly drops off as the battery goes flat. This can cause you an issue as your marker can suddenly go from a fully charged battery to a dead one with little warning so you may need to change more frequently just to ensure you don't go flat! I only play once a month on a casual non-tournament basis and have not had one go flat after shooting around 2,500 balls in a day. This is not your typical tourmanet usage so I will rely on others to provide more useful numbers.
Hope this is of use.
