Occasionally, subsonic ammunition doesn't generate enough recoil energy to operate a semi-auto rifle. In my testing, I had no issues with the ammunition failing to cycle the actions on two different semi-auto rifles.
Overall test results were good. It would have been nice to see a tighter group on our test target, but not all rifles like all ammunition brands equally. Luckily for us there are many different ammunition options available so we can find what works best in our specific rifle.
Velocity was right on the mark with manufacturers specification, and on target kinetic energy at 25 yards appears sufficient to humanely harvest small game quarry.
With regard to the one bullet that failed to expand, I'm left scratching my head as to why. Logically, you would expect a bullet travelling faster than a bullet that successfully expanded would also expand. As we saw in this test, gel testing can yield results that defy logic. For me, that's part of what makes testing so interesting.
CCI Sub-Sonic functions reliably in my semi-auto rifles. It's accurate enough to meet my needs for small game hunting with iron sights at ranges out to 25 yards. It is noticeably quieter than using high velocity ammunition and does not appear to sacrifice terminal performance at the lower velocity. One other thing to like about this load is the price. When you can find it in-stock, it's usually at a retail price of $9.00 per box of 100.
This load has been a staple in my ammunition cabinet for many years, but I've never had a chance to gel test it. What I observed in the gel tests match what I've seen when using this load for small game hunting. It's a good one.