I tried to run mine the other day when it was -15*, and it needed full mini-mags to run. It was 45* today and it was cycling CCI quiets and suppressor.
CCI SV has been so hit and miss I quit buying it. Have been using lots of SK pistol match in the mark IV. It doesn't run at cold temps very well either though.
On the 3 I have, I noticed new out of the box they wanted full power (i.e. high velocity) ammo with the stock spring. Use some stronger ammo to break it in, and/or get a reduced power Volquartsen spring and guide rod. That'll help a lot with the softer subsonics anyway.
Also, some of the mags can use a little tweaking. Not all, but some. There are tutorials for this online.
And yeah, run it oiled, not dry. Internals and the bolt. Oil, not grease - oil cuts through the fouling.
The whole Ruger Mk I-IV series is quieter than most of the competition because the bolt is contained inside the receiver with a relatively small ejection port, not because the bolt is "smaller". In direct comparison to the Buckmark, the Ruger series has less port pop and the bolt inside the receiver doesn't ring like the Buckmark slide.