Yeah, sp00n knows his stuff.
45 degree Sears - On contact, they grind together, eventually becoming smaller and smaller. So it just all goes wrong with high forces.
So you change that to a 90 degree trigger system, therefore there is not this grinding problem with the high forces.
Which leads on to needing a 90 degree piston to go along with the 90 Trigger.
Then as Sp00n stated, the cylinder.
There are a lot of guides, so just have a little Google around.