I know this is not a common situation in the US, but I am having a sound moderator fitted to my Sako 221 Rem and would like to shoot subsonic loads of about 50 grain bullets.
Please give some tips or point me to a website. Hodgdon does not supply subsonics. (US powders are different to our's anyway)
Also, is there any reason that my rifle will not like 50gr subsonic loads if it does not shoot supersonic 50 grainers particularly well? It shoots 40gr V Maxes very well.

I am in the process of getting a suppressor licensed for a .221, however I don't intend to attempt subsonic loads in it. I suspect that getting that slow will be a real challenge.

Assuming that you have access to a chronograph so you can actually know what you're doing, I would suggest starting out with just a few grains of Alliant Unique powder. It has always been fairly adaptable to very light reduced loads. I'm a great believer in Blue Dot for slightly reduced loads, but I don't think it would work to go all the way down to 1100 fps or so. Maybe Seafire, our resident Blue Dot expert, has done some research in this area and can chime in.

Bullet stability is a function of not just twist but of RPM's (revolutions per minute). When you slow a bullet down from 3000 fps to roughly one-third that speed then you have also proportionally slowed its RPMs. A "normal" twist may not be fast enough to stabilize the bullet as subsonic speeds.

Thanks Stonecreek. I have seen subsonic loads for the 221 but have misplaced the article. I will get info from the local powder manufacturer.

Even if you get subsonic data for the fireball, you still need a chronograph to ensure your speed is just under the speed of sound and not too slow. I have loaded subsonic for my 223 remington and 22 k-hornet. At 1000 fps (305 mps) a 1-9 twist worked well for 70 soft point bullets, but the 1-12 in the hornet was no good. I used about 7 grains of H110 (like N110) for the 223 remington.

I think that the subsonic 223 remington is much louder than the 22 rimfire subsonics, or even the supersonic loads when suppressed. I like shooting full power 2800 fps 62 grain bullets instead.

I like the heavier cartridges like the 300, 338 and 510 whisper and the 458 socom when shooting subsonic.

Ranb

if you can get some Trail Boss or maybe Unique or Green Dot, you can easily make subsonic loads with those powders...

consult a cast bullet manual...