I cringe when I hear people using trailboss with jacketed projectiles, may as well just load solid lumps of metal you won't get any expansion. It's good with cast bullets but a waste with anything else in my opinion.
Yes in the 243 you should get way more velocity with 55 gr projectiles, your figures are more like what youd expect to get for a 223 even then they're a bit light.
Oh I see you have corrected it and I guess you don't have access to a chrony. Just be aware Book figures rarely match real world measurement due to differing barrel lengths, leades, and bore and chamber dimensions.
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