Re: .308 Reloading & Barrel length
You are going to want to go with a faster burning powder. I use IMR4198 in my 20" Scout and 110gr. bullets.
Since you are using a semi-auto, you should look for powders that burn at a rate your action can handle. Too fast or too slow powders can be unsafe when it comes to cycling the action. For example, I can only use powders between 3031 and 4064 for my M1A as faster or slower powders won't allow the action to cycle or may cause unsafe conditions. Am guessing that your rifle also likes a particular range of powders.
Try a Google search for AR10 powders and loads.
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