The Vanguard has a 1:12 twist. 55 grain is pretty much max. 45 & 50 grain would probably work better. The Savage Axis has a 1:9 twist and will handle 55 and 62 grain possibly up to 70 grain. DO NOT shoot 5.56X45 NATO in a 223 chamber. The NATO rounds are higher pressure and the 223 chamber has too short a leade. If you want to shoot NATO get a Mossberg MVP. It has a 5.56X45 chamber and takes AR mags.
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