2.8x1.8mm but 006 is what I used on mine too. Download the Bam 50 Bible. It’s got all the info you’d ever need. Bunch of mods and forum post from like 20 years ago when they were hot. I should dig out my b51 I never even put it on paper
My FT club the SVFTC has had a B50 .177 as our loaner gun for @ 7-8 years now. Modified by myself for a fellow club member being regulated, light hammer etc, he moved on to a nicer rifle giving said B50 to the club ... it has proven itself as quite a great rifle & very accurate too.
easy to work on ... as it is a very close copy of the Daystate Harrier & Huntsman models. If you can work on them you can work on a B50/51
Kinda forgot I owned it lol. I need to slap a scope on this sucker. It had some stuff done to it. I believe it was just gone over and barrel crowned, ect. I forget who did the work. I’m sure some of you would of know him. He use to sell these.