I was seeing high pressure signs with reduced loads. Sticky extraction. I measured the Woodleigh bullets at 0.511 and the end of the barrel at 0.5085 to 0.509. I know it wasn't scientific but I can get 0.375 on my H&H.
Would this tight barrel make the pressures jump that much? If it is closer to 0.509 than 0.510 the I will try barnes bullets as they are 0.509.

My that is a tight barrel. Who made that barrel?
Sure could raise pressures with a .511" bullet thta obturates completely and has to squeeze down .0025" also.
Might be perfect for Barnes bullets. I have measured some of the TSXs at .5085".

I have also run some .512" GSC HV .510/450-grainers through a Lee custom bullet sizer made up for me at .510".
Worked like a charm.

The full bearing Woodleighs would be harder to push through the sizer, and might have some spring back.

But you could get .508" and .509" sizers made by Lee and see if two stepping it down to .508" springs back to .5085".

Its a Bevan King barrel made in Dawson Creek BC. I will have to make double sure on the measurements but will probably try tha TSX's anyhow.

I believe once the rifling has been established the pressure is still low and it would not be a problem. It is merely swegging of metal in this case copper which is soft. There is a patent #2687591 for taper bores. I have the pdf file I could send you by email if you wish but I am not able to post it here