Blank .303 L10 was for use in Bren Guns with a specially modified Blank firing Barrel. Two Pins were placed just in front of the Throat of the Barrel, to crush the Wooden Bullet.
Whilst this was effective in maintaining the Blank fire Capacity initially, ( the Mass of Crushed wood fibres formed enough of a “wad” to permit Gas pressure to work the gun) Flame cutting eventually fragmented the two cross Pins, causing (a) two projectiles exiting the barrel and (b) failure of operation of the gun.
IN theory, the two pins prevented the in-advertent use of “Ball” ( gun would blow up)…but in the end , with the Bren Gun going out of service in .303 ( replaced by the 7,62mm MAG, and the 7,62 Converted Bren, the L10 Blank ammo was redundant, in both Britain and Canada. ( Australia never adopted it, nor fitted the "Blank Firing Bren " Barrel.).
Why RG was still making it in 1967 is a mystery to me…Cadet use, Maybe?
For designs of the BF Barrel for Bren Guns, see “The Bren Gun Story” ( Collector Grade Publications ) which has the specifications for the location and size of the Cross Pins…
Of course, in Movie work, “Wood Bullet Blanks” are Prohibited, and we use Muzzle-fitted BFA screws, and Long (Brass) .303 Blanks. NO "Cross Pinning " of barrels is permitted either ( not by Law, but by Insurance concerns, and indirectly by “Workplace Health and Safety” Norms.
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