What magazines do you guys use and.what is your experience with reliability and durability?
I've used Hexmags, Brownells, Magpul, ASC, PRI and Lancer mags. I've used the first 3 for classes and the range and the last 3 at the range only.
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I've never had a problem with the Hexmag Gen 2 series. I've run those in 2 day classes and 4 day classes. Their first mags had some issues but they fixed them. If I recall correctly those wouldn't drop free all the time. They also tended to bulge when filled to capacity.
No problems with the Brownells mags. (30 rounders or those limited to 10 rounds with Magazine Blocks brand blocks- California) They feed well and drop freely. I have one lower that has a tight mag well. Brownells (and ASC mags will drop freely whereas some of my Magpuls/Hexmags hang up a bit. (only in that rifle)
Magpul Gen3 are great. I had an issue during a class with one of their Gen2 mags. Tossed it and popped in a Gen3 and gun ran perfectly again. No problems with Gen3 at all. 30 rounders, 20 rounders and 10 rounders are all good to go.
No problems with ASC mags except that their 10 round mags (30 round body and 10 round body) only hold 9 rounds. You can force a 10th round in some of them but you can expect problems-dented top cartridge and feed problems. Standard capacity work fine.
I have some PRI mags for 6.8 SPC. They work well over all. I've had one problem with one of them and that could have been ammo related. They are made to allow for the longer loads you can buy/load and I had a problem with one of those. Not sure I'd pay the premium price for those for 5.56 when Brownells, Hexmags or Magpuls are so much cheaper. On sale, you can get three mags for what it costs for one PRI.
I only have a couple of Lancer mags but they've given me no trouble.
Finally, if you have to go with 10 rounders and/or a magazine lock in your state, I'd go with the Magpul short mags. If you have a type three malfuntion, the baseplate is easy to remove. This happened to a guy at the range in the lane next to me. He had a magazine lock and the double feed caused the bolt carrier to get stuck halfway into the buffer tube - no way to separate the upper and lower. I had a screwdriver in my bag and was able to pop the base plate off for him so the spring, follower and remaining rounds would drop free. We were able to work the stuck rounds loose after that. 5 minutes at the range and no big deal. Probably a huge problem in a self preservation scenario.
I'm from California so I've got plenty of experience with 10 rounders. When I go out of state for classes I'm able to use 30 rounders. I just pack mag blocks and epoxy. After the class, I block them before I return. It's a pain but at least I get more mags for the range here.
Hope this helps.