I hope the mods don't consider this a dupe, as this thread is a full review/writeup, and the other recent thread was an inquiry.

Just a little less than a year ago, I went to a gun show for the first time, and I found some oddball magazines that, in spite of having been a member of this site for a while, and a lurker even longer, and having done a lot of my own shopping around/research etc, and thought I knew of just about every AR magazine there is - I had never seen or heard of some magazines I found at this gunshow

They are made in Bulgaria by a company called ISD, and are a 35rd polymer magazine with anti tilt follower and steel reinforced feed lips. I bought a couple of them solely because I had never seen or heard of them, and I figured that I would try a couple so I could contribute information about them at this site.

First I'll start with initial impressions & observations:

They are longer than you'd think they'd be for holding just 5rd more than typical 30rd mags, and they also feel a little heavier than you'd think too. Below are pics showing one next to a 30rd PMag, as well as inserted into my rifle for comparison:











The ISD magazines have a similar 2-piece floorplate/baseplate design as the PMags, with a raised "button" on the floorplate that protrudes into a corresponding hole in the baseplate, though the ISD's baseplate slides on/off from the rear, whereas the PMag's baseplate slides on/off the front.

The one qualm I have with the ISD mag's baseplate is that the edges/corners are not as round/blunt as on the PMag, and so with the rifle in a low ready position, it tends to dig into me more uncomfortably than the PMag, and more irritatingly is if I'm not careful, it can scratch my belt.

Baseplate comparison:



The anti-tilt follower isn't quite as tilt resistant as those of the PMag, but tilt is still slight even if you push down on one end of it to try to make it tilt, so I would say it works good enough. The design of the follower is unique AFAIK, and is a sort of a box shape with open front:







The back of the follower is slightly curved to slide properly in the curved magazine body, but I forgot to get a picture of it from an angle that would show this.

So that mostly covers the design, but how about how well it actually interfaces with the rifle?

The two that I have fit very tight in my lower receiver, which although it is an Olympic arms lower which are commonly known for tight magwells, PMags, which are known for being max-spec/tight fitting, drop free from my particular lower. Go figure. Although the ISD mags don't fit so tight that they are hard to insert, they do not drop free and must be pulled out. This isn't a problem IMO, because a proper reloading procedure should include stripping the magazine anyway, rather than relying on it falling out on it's own.

One point of concern that I only recently figured out when practicing reloading drills with these magazines is that they're easy to over-insert on an open bolt, in which case they can get stuck if you try to release the bolt without pulling the magazine back out slightly until it goes "click" into the proper position. What happens if you ty to release the bolt with one of these mags over-inserted is that not only will the bolt not release, but somehow the magazine will get stuck in the gun, and I couldn't get it out no matter how hard I tried, and the only way I could find to fix this was to lay the gun down, and pound the bolt catch with a plastic hammer I had, which presumably due to brute force causes the bolt catch to displace the folower on the over-inseted magazine, which is causing excessive upward pressure trying to push the bolt catch up, and when I did this, it also forced the mag into a properly seated position.

One thing that backs up this theory is that because the back of the follower where it would push up the bolt catch has a tab that sticks up higher than the surface of the follower, whereas other magazine followers do not, and so I thought to trim this tab ~0.5-1mm figuring that being shorter/not siting so high it could not put so much pressure on the bolt catch, and then see if I would still have trouble releasing the bolt with the mag over-inserted, which worked, as it now takes a lot less force to release the bolt on an over-inserted mag. However I'm still not sure if this was the culprit, as before I did this, when I was at the range actually using these mags loaded, in which case the follower is nowhere near the bolt catch, I still had one time where one of these mags got stuck and I could not release the bolt - I had to lay the rifle down on a table, pointed downrange, safety on, loaded mag in place, and pound the bolt catch to un-fuck it, and in the process chamber a live round. Not good.

Because of this, it is NOT a good idea if using these mags, to use the old-school push/slap method when reloading, if you do, you're asking for trouble, instead you should use the push/pull method which is the method that I use anyway.

FWIW I actually tried to over-insert PMags, and could not get them to do so.

So finally on 10/31/11 I got to actually shoot with these magazines, and see how well then functioned.

I loaded each to full capacity and shot them, twice, making my limited test 70rds through each, and I did have two malfunctions.

One of which didn't really stop anything, nor would have required remedial actions taking you out of a fight if it had occurred in such a scenario, just something it wasn't supposed to do; it locked the bolt back when there was still a round in the magazine, probably the fault of the aforementioned tab on the rear of the follower sticking up a little too far, which as previously mentioned has since been shortened.

The other was an FTF, in which a round was pushed about half-way forward, tilted up, and was stuck in the magazine sticking up. I removed the mag, pushed the round back in the magazine, inserted the mag and released the bolt, and it worked fine after that.

So 2 out of 140 rounds I had a problem which translates to 98.57% reliable vs 1.43% failure.

Conclusion:

I have mixed feelings about these magazines, Except for 2 out of 140 they worked fine, and they appear to be fairly well made, but the pointy edges on the baseplate are annoying.

They are easy to over-insert and can get stuck and even make the bolt stuck if they are over-inserted, but this can easily be mitigated with some slight tweaking as mentioned @the tab on the back of the follower.

Of the 2 malfunctions I had, one probably won't happen again due to shortening that tab, and the other I speculate might have been caused, or exacerbated by lack of lube, as they were dry and the feedlips felt a bit rough when I was loading these mags, and excessive friction might have been the reason for the 1 FTF, and maybe a tiny drop of oil on each feedlip would have prevented it.

I am not sure at this point if I would trust these mags for serious use/SHTF etc.

Did I miss the part about price?

lol

I can see buying one for novelty.

At that price that's where I'd stop with an unknown, though.

Please let us know how reliable it end up being.

The follower looks like an AK follower. It would have been neat if they used an AK style spring.

Thanks for the review.

I just got two of them to try...
They are very difficult to insert in the magwell of my CavArms lower. Too much force is exerted to seat them. They will not drop free.
Will NOT lock back the BCG.

They fit fine in my RR M16 and will lock back the BCG.
My next step is to try live fire.

ETA - they are shorter than my CP 40 rounders.

FWIW, in the other thread someone mentioned having trimmed/shortened the followers of some of these mags, and got them to reliably hold/feed 39rds.

I got them from CDNN.
They are not radically shorter than a CP 40 rounder....maybe about an inch or so.

A little update about tweaking these mags and figuring out whats going on when they're over-inserted:

Since posting this thread, I fiddled with these a bit more, and have almost completely removed the tabs mentioned in the OP, so that the rear of the follower is more like most standard designs, and this has further reduced the force needed to release the bolt on an over-inserted empty mag.

In further attempts to figure out whats going on, I tried releasing the bolt catch and slowly easing the bolt forward, observing through the ejection port, I found out that the bolt itself can get caught on the back of the feed lips on one of these mags when over-inserted, and as described in the OP, if the bolt is successfully released on an over-inserted mag, the mag moves down into the properly seated position, so I'm guessing that when the bolt slams into the mag, that is what knocks it down.

In an attempt to tweak this, I tried shaving the rear-tops of the feedlips to create a sort of slight "ramp" to help the bolt cam over an over-inserted mag, instead of getting caught on it, but this was unsuccessful as far as slowly easing the bolt forward as I did when trying to diagnose the problem, and I couldn't create any more of a ramp as I had already exposed the steel reenforcements in the feedlips, and as previously mentioned, the bolt was already able to knock the mag down even without the ramps.

I'll try to get some pics later demonstrating what I did to them.

I've got a couple of these that I played with a couple years ago. I don't use them much anymore.

One thing to note is that you can trim the follower skirts and get 38 rounds in these and still get them to seat easily in a rifle with a closed bolt. That's the good thing.

The bad thing is that I found the feed lips to crack. Now my mags are older and I hope ISD has tweaked the design slightly. Please keep an eye on things and let us know if your mags develop cracks along the back edges of the lips.

Not mentioned (I think I've got the only five in the country) are the steel 30rd mags mde by ISD. I've had my five for over two years and have found them to be durable and reliable. The followers look very much like the followers used in the plastic 35-rounders. Internally, the mags have plenty of room for dirt and crud to accumulate and still allow the follower and rounds to pass freely. The base plates are retained with a push button and the mags are pretty much the same size/shape as a standard GI mag. The only exception to this is that the base plate is sligthly wider since it slides over the sides of the magazine tube rather thin inside the magazine tube like a GI mag.

I don't think so. The Bulgarian spring and follower are quite a bit different from their USGI counterparts.

Bought one just so I could get free shipping from CDNN. We'll see.