Hi All, I'm working up a deer load for an aftermarket 5.5" barrel with good case support in my M20SF. I've long loaded 10mm for my 610 for years with great results. Given that loading manuals and on line specs show the max OAL for the .45ACP round at 1.275 and factory loaded Hornady +P 230 gr XTP's run around 1.35 and seem to work just fine in M21s, why could we not load 10mm longer for the Glock large frame magazine? I've seated several dummy rounds of 200 gr. XTPs (I have a boatload of 'em I bought at the factory as cosmetic seconds for $6 a box muhahahahah) out to 1.275. They seat fully in the chamber and after pressing in and still rotate freely so I know I'm not engraving yet. They hand cycle with out a problem and still have a bit of play fore & aft when stacked in a mag. The 200 XTP still has considerably more bullet in the case than a 180 XPT loaded to 1.26 (even more of those purchased for the same amount.) My thought is to start with an OAL of 1.274, 13.3 gr AA#9 (hand weighed) and build a pressure series up in .2 gr increments. I'm using new brass with Win. standard primers, a Wolff steel rod & 22lb spring. Am I overlooking something? Is there a fault in my logic? I'm in Iowa, and we have some dang thick whitetails here, I want to reliably shoot T&T a broadside monster's boiler room @ 50 yards. TIA X (the Centimeter Guy) Wanna kill these ads? We can help!