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Lots of cracked slides these days caused by less than perfect metallurgy, hardness, fitting, etc.. compounded by high pressure 9major loads. My goal in developing a great load is to maximize performance while NOT destroying me or my gun. The common sense recommendation is to use a slower powder to reduce case pressure. OK, slower powders measured & ranked how? Powder manufacturers charts are considered 'guidelines' as to 'relative' burn rates, and should maybe be considered most accurate with their own product? Add to this, the different burn rate charts available have conflicting ranks among the most popular powders used for 9major. And now for the rule of thumb Slower powders usually require more charge weight than fast powders to achieve the same velocity (assuming same bullet, barrel, primer & cart.). More conflict. So all of this has got me thinking... (probably over-thinking) The following is compiled from my own 9major load data over the years. This is a high level comparison - not a true apples to apples, since this is with 4 different barrel configurations, different temps, etc.. The last column is the charge weight of a 100% full 9mm case. Nice for relative density comparisons.
I've tried AA#7 a few times over the years in various open guns but have steered away from it each time due to it being dirty and worried that it would hurt the reliability of my gun. Earlier this year, I worked up some major PF 9 loads for my CK gun with MG 115 & 124's. Gun tracked great with these loads, but I had 1 malfunction where some of the unburnt particles got into my trigger bow area and limiting trigger travel so that I could not break shot. Not for me... I found the particle in the trigger bow area and saved it. Looked like a tiny blackened piece of corn cob. I've since found similar particles in my slide and other places they don't belong while shooting HS-6. One day reloading, I figured out where these particles are REALLY coming from - my JHP bullets! Seems that the bullets are tumbled as final cleanup prior to being boxed & shipped. My point here is, I wrongly pinned that failure to fire on the powder. AA#7 has a lot of great qualities for 9 major. - lots of gas works comp very well - slow (below 3N38 on all the burn rate charts I've seen, added safety factor at major PF) - very dense (13.8 grains fit in a 9mm case full to top) - easy to load fast (my 10.7 grain load doesn't fill case so much that I need to slow down) - inexpensive compared to VV, about the same cost as WAC & HS-6. problem areas - dirty - how dirty is it ? see pics below - very dense and fine grained - leaks a little around regular Dillon powder bar (plastic Arrendondo bar is much better) HOW DIRTY is AA#7 compared to HS-6? I worked up some 174 PF 115 loads for my guns and wanted to test how dirty AA#7 is compared to the HS-6 I've been shooting all summer. Granted, HS-6 is considered by many as dirty, but I haven't had any malfunctions attributed to it either. For this test, I started with 2 clean guns, 200 AA#7 (174PF-115) rounds & 200 HS-6 (174PF-115) rounds. Shot only the AA#7 in one gun and only HS-6 in the other. Disassembled & cleaned both guns after the practice session; taking pics along the way. First off, a recent pic of some offending particles sneaking their way into my gun via the JHP.