Have a Lithgowicon No1Mk3* I bought several months ago, all matching and in good condition. bore is dark and a bit rough but strong rifling (5 groove)

I cant seem to get this gun to group well, even at 25 yards its like a shotgun, wondering if anyone had any advice I can try or recommendation for hand loads to try, here is what ive tried already

311 sierra match king with 38 to 43 grains of h380
316 208g noe cast bullet, 16 to 18 grains of 2400 (pure and #2 alloy)
311 175g #2 alloy cast bullet, 16 to 18 grains of 2400
308 150g jacketed hawk brand bullet, 40 grains of h380 (halved the group at 25y but still a 3 inch group)

Tried Sellier and Bellot and Prvi Partizan factory ammo and couldn't get better than 7 inches at 50y

I really like this rifle and want her to be a better shooter, any help is much appreciated.
I am still relatively new to reloading
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