According to Mr Bulk's enclosed sheet with the Super LGI,
"The SLGI is already steeply overdriven and the use of lithum and rechargeable batteries is not recommended."
I've been using Energizer nimhs for quite a while now. It gets hot (not uncomfortably hot)after 10 minutes of continuous use. I've used it a few times for 15 minutes continuously without adverse effects. But as rookie said, do do at your own risk.
Ive heard it told that if you let the rechargeables sit for a day before using them you SHOULD be OK. They seem to be a bit "hot" for the LGI right out of the charger..let them "age" a day before using them .