Table at p.261 says that the arsenal project required for scrap pistols and rifles to be available at the Arc, but gearheads can construct them from junk, and the arsenal's description says about "breech-loading" firearms, not the scrap ones...
Where is mistake?
UPD
p. 87 says "Scrap weapons can be constructed by a Gearhead (page 55)." Should't it be "Jury-Rigged weapons can be constructed by a Gearhead (page 55)." instead, like in "Comment" column?