IMR 4451 and RL16 are both temperature insensitive. From the testing I've seen RL16 has just as good or better temperature insensitivity than H4350 with greater velocities. I have moved on to RL26 with the 147g ELD-M which is a slower burning powder giving my 24" 2812 fps with no pressure...
The Lee Collette die is great to reduce runout. I also use a Redding body die to bump the shoulder, and a Forester micro seating die. This combination works great with very little runout. Check out the youtube videos from Vaughn Precision, Fortune Cookie45 and Ammosmith. You don't need a $280...
I crimp all my semi-autos. I use 77g Nosler Custom Competitions with Varget 24.0g, and was shooting out to 870 yrds with my Aero Precision M4E1 and 1x6 PA with hold overs.
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