I have been using Brownells 30 shot magazines and also their 20 shot straight side magazines and am totally satisfied with the performance.
They are offered with the choice of stainless steel or chrome silicone magazine springs and standard gree followers or you can order them with MagPul anti tilt followers and Ranger base plates for an additional charge.
I also have some magazines that I have fitted with CMMG stainless steel followers and braided wire chrome silicone magazine springs.
All of the magazines I have been using, and this includes a selection of all choices, have been totally reliable.
Brownells puts the standard magazines on sale for $12.50 regualrly and these are also some of the least expensive brand new magazines on the market.
I have two C-Products stainless steel magazine bodies fitted with CMMG stainless steel followers and braided wire springs and these are, as stated previously, built truck tough.
They show no signs of ever wearing out, are comparable to steel AK magazines for durability and the whole kit costs less than an H&K M16 magazine.
H&K magazines are very well made but when I can buy three 30 shot magazines for less than the cost of a single H&K magazine, I cannot justify the purchase.
I also have three MagPul PMags.
These too have proven reliable and drop free in all rifles, however, they do have a few issues.
When fully loaded I find that the cartridges rattle in the magazine body.
They require the included feed lip cover to protect the lips when fully loaded and stored.
Because of slight changes in dimensions these magazines do not fit well in standard M16 pouches, you have to use modern design Molle type pouches if you want a full compliment of magazines in the pouch.
All in all. what I have seen is that almost all current production magazines are hands and feet above any older magazines in quality and reliability.