[Thor]

To see if the load is hot enough, load one round and fire, does it lock the action open? If it does 5 times in a row, the ammo is hot enough for the main spring you have in it. If it is not closing, THEN you need a stronger main spring AND stronger ammo. But stay with factory loadings.

Try some Remington Golden Saber +p+, which propels a 124 gr bullet at 1250 fps. FIRST put in a Wolff #36 main spring (gunsprings.com) only around $10. While you are at it, if the mag spring is not really hard to depress, change that too! I would always try another magazine if feeding is a problem. I dont really recommend the +p+ with standard 4" barrels, but with an 8" it sure seems to help. Also check to see how far away the empties are being thrown, it they just dribble out, the load needs a little more power. This seems to be a problem with some 8" Barrel Lugers.