I haven't experimented with case fill specifically, but I find that TB sometimes 'tops out' at a velocity at which increasing the charge makes little more velocity, but can be worthwhile for better accuracy. No point in batching up lots of loads if they ain’t where I need em to be !! I’ll be letting you know when things really start to rock and roll.Ĭan anybody verify or refute whether lots of airspace in a TB load = lots of velocity deviation. simply to establish ballpark, and shared for the community due to their being not much else out there. Meawls wrote:That’s exactly what these loads were. I wouldn't hang my hat on the results of three-shot 'groups' either, but they're okay to get ballpark velocities so you know how close to subsonic you are.

4gn of Trailboss should put a 55gn jacketed bullet in the subsonic area, adjust to find the sweet spot, barrel length plays a role in your velocity, also whether you neck-size or FLS the brass. Use heavy bullets if you want subsonic, very light bullets need _extremely_ small charges to stay subsonic. by all accounts these tend to result in less velocity deviation. I also plan to substitute the BR primers for magnums once I’ve found a load that sits just below the barrier. All were groups of 3 fired at 100 metres. didn’t want to go much lower because it would leave quite an airspace in the cases, which by all accounts leads to increased deviation in velocities, which by all accounts leads to less accuracy. All loads with Federal match primers,and 5gns trailboss. For those interested, 20 clicks upwards from a “normal” 100M zero on a scope with 1/4” increments will get you on paper. and there’s not much info out there - frustrating. Meawls wrote:I’ve just lately started dabbling in this area. I’ll get back to you on these when I get opportunity to test. not to mention point of inability to stabilise in THAT barrel. I’ve loaded up identical loads for each rifle using 62gn Nosler Varmaggedons, and these should be much closer to the sound barrier. I was unsure whether these loads would stabilise in the 1:12 barrel. ?! Wouldn’t need to expand at all for easy day-long headshots. by boy-ohhh-boy were they fun to fire, especially in that massive VSSF! And how about exactly 1/2” at 100M.

Each of these loads easily exceed the speed of sound. several ballistic calculators will calculate this for you after the parameters are entered. I regard speed of sound at around 1080, but it’s variable dependant upon conditions. I’ve just lately started dabbling in this area.

Subsonic 223 rounds