Just a quick and very simple tutorial this time, there are several methods of creating convincing Praetorian Plasma Guns, at it's most complex you can remove a models lasgun and replace it with a plastic or metal Plasma Gun, at its simplist you can as I do use a plasma pistol (I use Imperial as it's the one I have available, a Chaos version works too however).
This conversion can potentially be done with a Lasgun, however I prefer to work from a Meltagun, though it makes for a larger weapon I feel it's appropriate for such a piece of kit.
I firstly snip the barrel, then making a horizontal cut along the seem of the weapon to the point where the ridge on the upper surface begins before making the vertical cut.
Next I prepare the pistol, firstly snipping the hand away cutting at an angle from the base of the grip upwards on both sides with a pair of snippers, then removing the resulting prism - alternatively a sharp scapel can be used to slice the hand away neatly including the trigger but leaving the small flask and it's mounting. The small detail on the right rear of the pistol is then removed before snipping or slicing the rear portion of the pistol off neatly where the sloping surface reaches the top.
You should now find the two components will slot together fairly neatly and can be glued in placed, if however the surfaces are not level ensure they are, center the weapon as best you can (there is a slight overhang as the Plasma Pistol is a fraction larger) making sure when glued it dries upright and not at an angle.
Finally you'll probably need a little putty to fill gaps, smoothing them over and then probably trimming a little once dry, the picture below gives an idea as to where the putty will likely be needed though I must emphasise this has not yet been trimmed and tidied. Once that is done, your ready to undercoat and paint, job done!