QUOTE (Lance Jackass @ Nov 19 2006, 02:29 PM)
Whats this "white paint balancing mark" mate?
With a GPMG variant that has the normal adjustable gas regulator it is necessary to "Balance" the gun, that is to set up the relationship between the gas regulator and return spring correctly so the weapon functions safely at the optimum rate. The trigger group on the GPMG has two sears, the normal (rear) sear and the forward "safety sear". The safety was brought in after instances of short travel of the working parts caused them to miss being caught by the sear. This change turned the L7A1 into the current L7A2. A white line is painted on the right hand side of the body to indicate the position of the rear sear.
Basically during balancing a number of short bursts are fired after each burst the cocking handle is pulled to the rear, if it lines up with the paint mark the working parts are caught on the rear sear, if it stops just forward of the paint mark they are on the safety sear. Each time the cocking handle aligns with the paint mark the gas regulator is adjusted to reduce the gas flow by the number of clicks specified (4 I think but I'd have to check with the AESP) in the procedure until the working parts are caught by the safety sear. Once it is caught on the safety sear the gas regulator is adjusted back in two clicks, checked that there still four more clicks of increased gas movement left and another burst fired to ensure the rear sear is engaged. This procedure ensures that the nominal rate of fire of approx 750rpm is achieved to avoid undue stress on the weapon and that there is sufficient gas adjustment left to cope with carbon fouling if the weapon then has heavy use. If you ever encounter a GPMG on which the balance setting is unknown the default gas regulator setting is 6. The gas regulator has 9 detents, when fully screwed in it should read 0 which is full gas directed to the gas piston, on a clean weapon that would give an obscene rate of fire and put undue stress on the gun.
Edited by Tarnish, 25 November 2006 - 02:05 PM.