Stijn, if you can get it I would recommend using Hodgdons' HP-38. It's the same powder as ww231 only less expensive. Burns very clean. Hodgdon owns the Winchester powder business now and all their powders are made by Hodgdon.
AA-7 is actually a little slow for the 45ACP, this and other powders at this point on the Burn-Chart may be what's causing your problem. 45ACP is a low intensity cartridge and powders for it should be on the fast side. There's not enough pressure-build to burn slower powders. If you want to stick with Alliant powder, I would recommend AA-5.
As for your spring, it should last about 3000 rounds or so, should be a 16lb.spring and the closed-end should go around the Guide-rod for proper operation.
What are using to lube the slide with? Either run it wet or use a good gun-grease like Plastilube or Tetra-Lube.
At this point, it seems that you have a fairly new gun and it's just breaking in. However, unburnt powder from the AA-7 and the lube you're using could be forming a sludge that's slowing down the slide.
One more thing it might be, what is your crimp diameter at the casemouth, should measure .470-.472.
Dave
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Last edited by Dave Waits; 02-09-2012 at 01:08 PM.
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