Carteach and I just tried the same ammunition, Aguila SSS. His results were not positive — poor accuracy with bullets not even stabilizing. My results were a result of considerable research and quite positive.
I tried SSS in a couple of pistols but the results were mixed. I decided that the solution would be to fire it through a .223 upper with CMMG conversion kit. Turns out people have done that with good results, as the faster twist barrels provide decent accuracy. However, my goal was to have a quiet round and SSS isn’t quiet when fired from semi-auto rifles. The short case means that the gas comes out of the ejection port quite early in the cycle.
While searching the web, I noticed that several owners of Mossberg 144 rifles shoot SSS with good accuracy. While the twist rate is supposed to be the same as with other .22s, something about that gun makes it work better. I have a 144LSA and tried the 60-grainers unsuppressed first. Accuracy was excellent at 25m, with no keyholing noticed. After I fired ten rounds to verify stabilization, I put the AAC Aviator suppressor back on and tried again.
Accuracy from kneeling at 25m remained excellent, with all holes touching. I fired it at 75m also but I was not firing on paper. Instead, I had a pop can on top of a steel post. It seems the point of impact moved slightly to the right relative to 40gr bullets, once I corrected for that I could ring the steel consistently. I only hit the can once out of ten shots, so I have no idea just how much drop it had at that distance with 25m zero. 5-6″ drop seems likely. It might make sense to replace the 4x Leupold with its duplex reticle with the upcoming Primary Arms 4x with BDC chart and just learn which hash mark corresponds to which distance.
The point of this whole exercise was to try out a relatively effective load (50% heavier than most subsonic .22s) in a bolt action and check accuracy (passed) and the noise level. SSS is already fairly quiet without a can from such a long barrel, but with the suppressor it was QUIET. It was quieter than “Hollywood quiet”. It made as little noise on firing as clicking of a mechanical pen, just lower in pitch. Certainly quieter than any air gun I’ve encountered. The sound of the bullet hitting the earthen backstop at 75-80m was far louder.
SSS is dirty ammunition. But it is super quiet and apparently fairly effective on impact. Might make a low-budget alternative to subsonic .223 loads.