Hamilton also said he preferred 9mm bullets, the type that he used in the massacre, and told how he tested bullets to see which were the least prone to jamming.
Although Hamilton never drank, he said he had experimentally studied the effect of alcohol on his accuracy while shooting, Ian Boal told the inquiry.
Mr Boal, 22, a student who helped out in Hamilton's clubs, said he knew Hamilton had been interested in guns but thought that interest had lapsed.
But around Christmas, Hamilton told him he was "heavily involved" in his guns."He used to talk about the spray of a bullet, what a bullet could do," Mr Boal said. Hamilton also used to talk to Mr Boal of testing bullets and described shooting at books at a target range, to assess the "spray" of a bullet through their thickness.
Mr Boal told Ian Bonomy QC, for the Crown, that Hamilton talked about the penetration of bullets. "He talked about how a bullet would penetrate 30cm. His words were `through someone'," Mr Boal said.
After an incident in January he got a letter from Hamilton criticising his teaching methods and he told Hamilton he would be quitting at Easter. But Mr Boal, who met Hamilton when he responded to an advertisement for a sports coach at a summer camp, said that apart from his talk about guns, he saw no change in Hamilton's behaviour in the period leading up to the massacre.
Mr Boal responded to the advertisement in 1994 and helped out at a summer camp at Dunblane High School that year. He noticed the sleeping arrangements were odd - they all slept in the common room.Hamilton would insist they wore black swimming trunks for some activities, he said.
The inquiry continues today, when Scottish Secretary Michael Forsyth, MP for Stirling, and his Labour shadow, George Robertson, who lives in Dunblane, will give evidence.
tStunned police seized a Nato forces SA-80 assault rifle when they raided a stall at a school bootfair. A member of the public overheard the man trying to sell the weapon at the King Ethelbert School, in Birchington, Kent, on Sunday. Det Con Paul Risby said: "It is very worrying knowing this sort of weapon is available".Reuse content