Board Thread:General Nerf discussion/@comment-45439975-20200410000856/@comment-27306930-20200410052248

Hey Z, welcome to the wiki. 18650s are longer than C cell batteries and won't fit in the RapidStrike battery tray without some modification. Regular alkaline C and AAs are 50mm long. 18650 IMRs are 65mm long. Plus, you might have problems finding 18650 to C converter shells. Ask around, but I've never seen any.

What you really want to use is 14500 IMR batteries. They are exacly the same size as AA batteries. When you insert them into to C converters they slip in the RapidStrike tray without ANY modification. You'll also need a couple dummy batteries. The downside is 14500 capacities are rarely more than 2000mAh. Still, they work great and you can always carry spares.

All 4 cell flywheel blasters (AA, C, and D size) are pretty safe to use with two 3.7 volt IMRs. You will get a modest but very noticeable performance boost. Sometimes you might need to disable the thermistor (fuse) inside the blaster, but that's very rare when you're using just two IMRs.

Second, and most important, buy IMRs with Circuit Protection. It prevents the batteries from over charging, over discharging, and catching on fire. If unprotected IMR cells drop below 2.5 volts, there is a significant chance they will catch fire and explode the next time you charge them. So google "imr batteries vs protected" before you click Add to Cart.

Good luck. Post pics. Check back if you run into problems.