Re: M14 to AR10 mag question
I did it with a drill, my little friend the Dremel tool,(with the large, quick lock cutting wheels), and finished them with small files.
I also cut the notch into the top of the back of the magazines, into the retainer lug, using the same tools. My mag catch cuts were right on the money but I needlessly cut two of the mags a little deeper than necessary for the bolt's function. The other 3 are fine. You need to be most careful in laying out the mag catch slots and drill two holes, side by side then cut carefully and finish with the file to square everything up and deburr the inside of the tube to prevent hang ups. The fine file can take you to the right position; neither too high nor low, for correct feed geonmetry, so prepare for a little time to fine tune your cut: don't try to get there all at once.
All mine feed without problem. Measure twice, cut once!
There is no bolt stop function given the mag followers are for M14s and not AR-10s, so you'll have to pull and lock the carrier back to remove the mags. Sometimes the bolt actually knocks the follower out of position in the mag! So go easy on that cut and take only what the bolt needs and no more!
Armalite used to make replacement followers available but stopped a few years ago. Other outfits may make them now.
You can modify them and they will work as an inexpensive solution given the relatively low price you can find M14 mags at times. I use mine for practice mags but popped for a couple of the Armalite package deals, often available at 5 for $150.00.
Palmetto State Armory has the best prices I've ever seen on AR-10 mags but are out of stock at the moment.
http://www.palmettostatearmory.com/armalite.php Short answer is "YES You Can!"