I still go with my original post stating the trigger bow is at minimum tolerance and the magazines are at maximum. This would cause a harder trigger pull with magazine if it goes off at all. Some magazines will work some won't . Without a magazine it works fine .
Dauntedfutere is right being a light load. I know with a plated 158g bullet at 1.46 and 3.3 of solo was only a 85 PF. With a 147g I had to be in the mid 4's to get a 125 PF.
I'm shooting almost the same recipe but I'm 3.6g of solo1000 but my brass has been trimmed to .902-.906. I have great accuracy. My too had some cylinder rotating issues after some firing. I clean the cylinder and cone face after a bunch of rounds and now do not have that issue. My PC has very little space between the cone and cylinder if anything got to dirty in there it caused the problem. Much more space in my 686 and I think too much space on my 929
How do get blow by if the bullet is exact diameter to the barrel ? Some barrels are different I thought. A nine barrel can be .357 in actuality. So if you sized a 9 to .357 that's the same size as the barrel
What kind of bullets / powder?
I have 147 moly , 124 and 115 montanas some 160 bayous too, solo 1000 , hp38 , hs-6 powders . I've played around with some but she really runs slow
Is the disk indexing without the primers?
Is the disk fully indexing?
If it's indexing fully without the primers perhaps they are not dropping and try to clean the primer tube in the primer magazine
If it's not fully indexing perhaps the primer pin is dragging on the disk, meaning the pin is not fully retracting and may leave a mark on the bottom of the disk.
Either way a good cleaning never hurts
My steelmaster had the same issue. After scratching my head for a while I just called them. Without hesitation he new what it was. The trigger bow is at minimum tolerance and the mags are at max tolerance causing the bow to hit the magazines requiring a hard trigger pull. Just like sonofspartans said but this is how the tech at STI explained it to me. After replacing the bow it runs fine now.