I just did a low velocity test on the 338 caliber Hornady 225 grain SST projectile to see how it expands. I thought that this would be of interest to members who shoot a .338 caibre rifle.
A number of shots were fired and these projectiles are typical examples of the results that I obtained. The photo below shows a new SST alongside two projectiles that were fired into the same material at 1000 yards.
The mushroomed projectile was fired out of a .338 RUM and had an impact velicity of 1614 fps ave.
The one on the right was fired using a reduced load out of my .338WM and had a calculated impact velocity at 1000 yards of 1228 fps ave. At this low speed it also seemed to be unstable. Due to this instability near the transonic barrier, the bullet may have had a slightly lower impact velocity than calculated.
So from the results I would say that this bullet would still expand at a slightly slower velocity than 1600 fps, but it would be a bit unreliable. Better to stick to 1600 fps as the minimum impact velocity with this projectile.