it feeds flawless if you keep it clean, the mag is a standard AR-15 223 mag with the follower milled flat. A standard 20 round AR-15 mag holds 7 wssm rounds single stacked. the RSAUM mags are AR-10 mags. No experience with the RSAUM's, if I were to go with an AR-10 it would be rechambered by accuracy systems inc to a WSM chambering
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