I found a box of 53-grain V-Max I have for some reason, and loaded those in Federal cases over what Hodgdon shows as the max load of Trailboss, 4.0 grains. Five with CCI sr primers, and five with Remington 6 1/2. The latter are noted as not suitable for standard .223, but work great with things like .22 Hornet and .30 Carbine; since this is such a low pressure load I thought I'd give them a try.
The CCI loads gave an average velocity of 1096 fps, highest being 1126 and lowest 1048.
Remington loads averaged 1014fps, highest 1020 and the lowest 998. At 50 yards, the five on the bottom(aimed at the bull) were CCI primed,
Friend has a Silencerco Hybrid suppressor, and I was able to put these through it; no plugs needed, about as loud as a pellet rifle; with a can set up for .22 might be even a bit quieter.