Im on my 3rd barrel on my TTR1, it took me that long to get one i was happy with.
The original would only shoot Bisley Magnums / Baracuda Match acceptably. I bought a HW blank and its bore was all over the place, couldn't get decent results with anything (confirmed by phil d)
Now on a LW machined to 14 inch that shoots JSB Express very well, but still not found the perfect pellet (unless the Express is it)
It is pretty much pot luck.
On the subject of hammered barrels, i believe Cometa still make their own hammered barrels also. I had one years ago and speak as you find the barrel was very good with accupells at the time. The internals needed work, but the barrel would have been a good donor for a PCP.
Regards,
Rhys
Theoben TTR1 .177, Steven B Blue/Grey Laminate Stock, Nutshot Mod, Hawke Sidewinder 10x42 Tac IR
Daystate Pulsar. 177, Donny FL Sumo Mod, Pard NV008LRF