Milwaukee M12 Stubby Impact Wrench Review: Why the Battery Matters More Than You Think

Introduction

The Milwaukee M12 Stubby impact wrenches, models 2562 and 2563, have generated a lot of discussion, and opinions vary widely. After spending serious time with the tool, one thing became clear: the battery you pair with it changes the story dramatically. This motor is thirsty for power, and with the right pack it will happily give you everything it has.

Meet the M12 Stubby

The 2562 and 2563 sit in the compact class, and the general guidance holds: if your main job is breaking loose fasteners in the 100 to 350 ft-lbs range, this tool rocks through that range with impressive speed. If you specifically need to remove 550 ft-lbs fasteners regularly, stepping up to an M18 mid-torque is the better call.

In everyday use, including automotive lugs, interior work, and light tasks, the Stubby performs without issue and never felt like it was struggling.

The Battery Test: Six Packs, One Stubborn Bolt

To find out how the motor behaves under different power, we let the tool hammer on a large bolt that was not moving and recorded the voltage drop for each battery, from the CP 2.0 all the way up to the XC 6.0. The results were eye-opening.

Here is what happened. The CP 2.0 started at 12.41 volts and dropped to 8.09, and you could hear the impacts slow down noticeably. The CP 2.5 High Output held its own better, but stayed in the nines with a low of 8.94 volts. The XC 4.0, a 2P battery, started at 12.38 volts and sank to 8.54 and was still dropping, which was better but not by much. The XC 6.0 started at 12.15 and fell to 8.75, and it could have continued down. That one was a genuine surprise, since the 6.0 has done well in normal use, but sustained hammering on a single bolt exposed it.

Then there is the XC 5.0 High Output. It started at 12.39 volts, dropped to just 10.22 volts at its lowest point, and held there. It did not keep sinking like the others. The difference in impacts per minute was audible too, and the 5.0 clearly outperformed every other pack in the lineup.

Why the XC 5.0 High Output Stands Out

The takeaway is simple: if you want power from any Milwaukee M12 tool, the XC 5.0 High Output is the battery to pick up. It held voltage under load where every other pack sagged, and the difference in how the tool sounds and hits is obvious. There is also a practical detail worth knowing: the 5.0 has a slightly different shape on top, without the indentation the other packs have, which can matter for certain holders and testing rigs.

The honest surprise in this test was how poorly some larger 2P batteries held up. There was no steady curve where bigger packs held voltage longer. This motor draws more amps than expected, and only the 5.0 High Output kept pace.

Heat Build-Up Under Sustained Load

One more thing to know before buying. When you sit and hammer on a stubborn bolt for a long stretch, the tool gets warm, and the socket gets very hot too. In everyday use this never happened; the heat only showed up during this extended, full-load test. The thermal check after testing confirmed it: the 2.5 was warm, the 4.0 was cool, and the 6.0, which had dropped hard in voltage, ran hot. If your work means continuously pounding on suspension bolts or other large fasteners, the heat is worth considering, and stepping up a size class may be the better answer.

Buying Advice: Which Combination Makes Sense

If you are buying this tool specifically to remove 550 ft-lbs fasteners, go up to an M18 mid-torque instead. For the 100 to 350 ft-lbs range, this tool will more than satisfy you with how fast it removes and tightens fasteners.

On batteries, the recommendation is straightforward: buy the kit rather than the bare tool. The kit includes the 2.5 Ah High Output and the 5.0 Ah High Output batteries, and that combination is well worth the extra money. You get the 5.0 for maximum power, and when you want something smaller and lighter, the 2.5 High Output is not far behind in performance.

A lot of buyers pick up this tool without the 5.0 High Output battery, and that is exactly the combination that leaves performance on the table. If you want everything the Stubby can give, pair it with the 5.0.

Conclusion

The Milwaukee M12 Stubby 2562 and 2563 are excellent compact impact wrenches for fastener work in the 100 to 350 ft-lbs range, but this testing showed that the battery is the real headline. The XC 5.0 High Output held voltage under load where every other pack sagged, and it made the tool noticeably faster and stronger. Buy the kit with the 2.5 and 5.0 High Output packs, use the Stubby for its intended range, and you will be very happy with the speed and power it delivers.