"I have had these for a few months along side the PMAGs as well. So if you're looking for an opinion on which to get, I'll go a bit more into detail to possibly help decide. I am using the stock G&P bolt and nozzle for those curious.
(keep in mind these are STANAG styled):
STANAG: heavy and sleek in hand, feels great if you like the traditional look.
PMAG: feels natural in hand, but not as heavy as the STANAG, but comes with a nice, tight base plate that covers the fill valve.
STANAG: has pins to punch out, but from what I've seen so far I don't need to take them apart, just keep the seal on the bottom lubed.
PMAG: the unholy Christ of magazines. On the bottom it has one long screw, once this is out, the magazine will split into three pieces. there is a metal rod to hold the spring in place for the follower, and o-rings on the magazine pieces to ensure a good seal. The problem with this though, is that even if you oil them well, they can still leak, and you may even have to replace them! Not only this, but re-assembling is just of a nightmare, having to make sure the spring isn't caught and the bar isn't in the way. It's an alright fit, so you'll either need some help in order to make sure it's put back together correctly, or get lucky and do it yourself.
STANAG: The fill valve is on the back, which is fine, but the valve itself is rather long, so long that you could put at least THREE(3) o-rings on the valve to cover it. This means that it may spray a bit more gas, as well as not coming with o-rings(it wouldn't make a difference anyway). Whether it's less gas efficient or not I'm not 100% sure, but I'm skeptical with it.
PMAG: done perfectly, has a o-ring on the valve, shallow, fills perfectly. it even has a base-plate to cover it.
Final verdict/pros & cons
The overall build is nice, I personally prefer the look of these over PMAGs, but they were sold out at the time. The fill valves may just be my problem, but it's a simple thing to look over considering how nice these are. All-in-all, I would get these mags over the PMAGs.
cheaper than the PMAGs
holds more rounds
feels better in hand (personally)
not much need for take down
fill valve on the back.
Hope this has helped those who are unsure!
"These mags are fantastic. I received the WOC Challenge kit a few years ago as a present, and got a few king arms mags with it (she didn't know that those mags don't work with the stock bolt) and they never work well. I've been wanting to have a full combat load out to actually play with this gun. We had a little extra money and I bought 11 of these mags (even though its going to get cold soon here in Colorado), I cant wait to try these out in the field.
I am so happy I went ahead a got these, the quality is fantastic. I have tested all of them and everyone of them works fantastically. Its been a little cold the last few days, and they still work to the last bb. Although I wouldn't run these in winter, I think I can for a few more months. Another aspect I like is the capacity, 50rds is a nice mix of milsim and usability.
I should point out that these are very heavy. For me this is fine, I am a grown strong man, however I could see this being a negative for smaller or younger people. For example, on my vest with a combat load, it weighs close to 30 pounds (just mags), I also run a cross draw M9 holster on my chest and a water bladder on the back. So for my load out it could be close to 40 or 45 pounds. I know that a true mil. load out is much heavier, but for airsoft thats pretty heavy. I honestly don't mind.
So enough with the gasbaggery, its time for the pros and cons:
Pro: Build quality
"If you need some magazines for your G&P WOC or Magna System GBBR and you live within the Continental United States, look no further. SAVE MONEY, buy these magazines while you can as these magazines purchased from overseas on your own can be more expensive if you are not planning to buy in bulk orders. These work great with the stock hammer spring, seat very easily with minimal to no filing required on the magazine catch and the base plates can be swapped out for more authentic magazine plates for those milsimmers out there.
Easy shipping within CONUS
Good seal with stock internals for G&P WOC
Cons: Paint will wear off quickly after a few skirmishes
Can never get enough of these!
Shell can be dented easily around the shroud located on the top of the rear part of the magazine if not handled properly (Like dropping it).