Stag model 5 will be my first deer hunting AR. Still 1-2 weeks out. I have good 6.8mags for it. Now I hope to buy a 5.56 upper at some point for plinking and the range (ammo cost). I know about feed problems caused when using a 5.56mag in a 6.8 upper. What would I expect If I were to run 5.56 ammo using the 6.8 mag. Should I have a set for each? Many Thanks!
Due to the shape of the follower and the ribs in the sides of the magazine they rounds start getting pretty loose as they are loaded up. Just take one of your 6.8 mags and start loading 5.56 rounds into it. Probably the biggest problem is that the follower will align the rounds improperly for proper feeding. I had a cheap steel 5.56 magazine that would not hold the rounds aligned and caused jams almost every time as it would allow them to pop out of the feed lips. Just load them and look at the alignment and feel how they are held in the lips and how they can be moved back up under the lips.
As stated in the previous post, 5.56 mags are cheap enough. If you live in a state that allows hi-cap mags, don't delay and buy some now while you still can. I've found some good quality mags valued anywhere from around $14 to $30.