henryo

1 in 7" twist as it will do everything. I shot every weight out of it and they never blew up. 1 in 8" is a slight comprimise for the heavies. Around 24 to 26" length. That will get you more or less all the velocity possible out of a 223. It's also worth getting it throated to the right length for the heavy bullet you want to use. You might end up single feeding them though. You can still get good accuracy with big jumps if you need to mag feed / lighter weights.

If it helps there is also data for the 82gr Berg with more or less the same charges at a shorter COAL: Can't tell you how to load your ammo but I think you have a fair margin - the 'max load' is standard commercial 55kpsi but Lapua brass + CCI 450 will take closer to 5.56 levels (60kpsi). Best thing to do is string a few over a chronograph to see where you are - every gun is different If it works for you at 50''' jump then go for it

Hodgdon website has the data: (Note the COAL on the 223/80gr) Would be interested to know how you get on with the 4166 as I've loaded some up for a .204 Ruger/39gr and I thought the grain size was massive. Ta H

Hi Martin I had a 30" barrel and 3500 to 3600 fps was quite achievable with the right powder for 52gr / 55gr e.g. RS40. The loads with RS52 maxed out at about 3350 fps with as much as I could get in the case (probably an unpublishable amount). I also noted that VV N140 was pretty close for velocities when loaded to the same charges as RS52 (RS52 was about 50fps faster on average). So you might be able check out the N140 data and compare with what you already have. They seem to show compressed loads as well. Incidentally I had that barrel cut down to 16" and a load with 52gr at 3500fps was reduced to 3180fps (that was IMR4198), which isn't bad I think. Kind Regards Henry

Hi Martin I tried RS52 with 55gr and couldn't get enough powder in the case, even with a compressed load, to reach good velocities. I used RS40 (same process, next burn rate up) instead which turned out perfect for 52 / 55gr. The RS52 is fantastic for the ~80gr bullets out of a long throated rifle. Kind Regards H

I wouldn't know but is it quite a mild load / slow powder? Sometimes too low a pressure will not make the case obturate fully in the chamber. Re. moderators they are known to create 'back pressure'. Not normally an issue with bolt guns but the Americans have to worry about it with their autos. Maybe also check for oil in the chamber as it needs to be dry for the brass to 'stick'. Would be interesting to know if your loads were neck sized only as it should be a close tolerance fit and you wouldn't expect these problems. H