Reloading help for No1Mk3*

[3rdTennCoC]

Have a Lithgow 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

Information

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[pisco]

Have you done a chamber cast what is the crown like

[Daan Kemp]

Have you tried 100m? The bullets might not be stabilising that close.

Many other possibilities but try one at a time.

[WillSarchet]

Try to obtain some MkVII ball and see how it patterns. If it still is shooting over 4 MOA, I'd consider that the rifle or the shooter is the issue. Look up the Instructions for Armourers either 1912 or 1931 and inspect the rifle as described. The bore could be worn out, forend warped, spring and plunger missing from the nose, inner band or nose spring worn out, etc.

[Brian Dick]

Guessing your barrel has been fired more than it's fair share with Mk.7 cordite ammo. Try switching the 174 SMK for the Sierra 180 grain Pro-Hunter or another flat base equivalent. Boat tail projectiles in well used LE barrels usually won't perform. It's because of the wear pattern in the throat/leade cased by cordite. Use a .310 plug gauge to check the barrel at the throat end. If it enters .25" or more, you need a new barrel.

[30Three]

I had a similar issue with a No1MkIII*; shooting over 12 MOA at 50 metres with SMK hand loads and PPU factory.
Barrel was worn at the muzzle and also poor fit of the wood. A replacement new old stock barrel got it half way there, and careful attention to the fit of the wood got it down to a proper 2 MOA.

[3rdTennCoC]

No chamber cast but had the muzzle recrowned, cant be shooter error, shooting from a bench. Ive heard of some crazy stuff before but how can bullets be so unstable at 25 to 50 yards and hit well or better at 100?
When I slugged the bore it was a bit larger than new but not so large that people say to replace it, some say replace it if the groove diameter is larger that .316 or .317 and its not that large

[browningautorifle]

Obviously the bullets aren't stabilizing so I suspect it's oversize. If they show stretched holes at 25 they won't be better at 100. Prove it to yourself, go out and do it.

[3rdTennCoC]

Obviously the bullets aren't stabilizing so I suspect it's oversize. If they show stretched holes at 25 they won't be better at 100. Prove it to yourself, go out and do it.

Thats what I figure but i never said the holes were stretched, im not seeing any keyholing

[browningautorifle]

By stretching I mean keyholes. The hole isn't round. Anyway, I suspect your barrel is oversize so you aren't getting accuracy.