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20rnd mags, straight vs. curved

5K views 33 replies 11 participants last post by  Pandaz3 
#1 ·
I am thinking about picking up some 20 round mags, and see they have straight and curved examples out there.
Stoner was fine with a straight mag at 20 round capacity. It wasn't until mags got larger that the curve came to be.

Is the difference just in tooling that manufacturers have available? or are their real performance differences between these two?

Would no-tilt followers come into play?
 
#7 ·
IIRC, that was a known problem on some of the Gen M2 20-rounders. I can't quite remember what was the underlying cause and my Google-Fu is failing me, but there actually was one (I found some of Will Larsen's old posts that alluded to the defect, but none addressed it specifically). Also according to Magpul, there isn't a way to truly implement an anti-tilt follower with their straight-bodied 20-rounders, which was why they went with curved for the Gen M3 20s as well.

Some of the really early Gen M3 20-rounders also had a tolerance stacking issue that affected the force that was needed to seat a fully loaded mag on a closed-bolt (so that in affected magazines, with certain ammo, the second round could nose-up alongside the first), but Magpul quickly remedied that one.
 
#8 ·
IIRC, that was a known problem on some of the Gen M2 20-rounders. I can't quite remember what was the underlying cause and my Google-Fu is failing me, but there actually was one (I found some of Will Larsen's old posts that alluded to the defect, but none addressed it specifically). Also according to Magpul, there isn't a way to truly implement an anti-tilt follower with their straight-bodied 20-rounders, which was why they went with curved for the Gen M3 20s as well.

Some of the really early Gen M3 20-rounders also had a tolerance stacking issue that affected the force that was needed to seat a fully loaded mag on a closed-bolt (so that in affected magazines, with certain ammo, the second round could nose-up alongside the first), but Magpul quickly remedied that one.
this is what I was thinking. with a straight body, the follower's tilt should change depending on how many rounds are in the mag to account for the taper..
 
#9 ·
At the gun show I visited Saturday, a guy had a table with Vietnam era mags. Several were the 20-round variety. Since that is what I used on both my combat tours 50 years ago, I thought I would pick up a few. I asked, “How much.” He said, “$45 each.” I kept walking.
 
#12 ·
I like the okay surefeed 20rd mags in grey or black teflon finish. They have been perfect. I do have a old 20rd straight pmag. Did have a occasional failure to lock open on empty but no feeding problems. The m3 curved 20rd mags have been gtg in my experience.
 
#16 ·
Try this helpful AR15 mag hint lost in the mists of time. Maybe longer. Take apart. Take OOOO steel wool and polish the insides. Polish the sides of the follower. Slobber up with Break Free or regular LSA. Let dry overnight.

Grab the spring and gently bend the rear coil ends to elongate that side of the spring. Bend the first two or three coils more. Bend the first coil sosss the coil wire rests upon the follower. This increases rear follower spring tension.

This seemed to work on cheapo USGI aluminmiummumm 30 round mags. May not work on 20 round mags. If your mags do not lock back the bolt, CONSIDER slightly trimming the bolt stop spring. Go slow here. Springs cheap.

Hope this helps. Hundreds of builds but long ago and far away. Now old and cooted. Yikes! :)
 
#19 · (Edited)
For metal aluminum mags, straight mags are the old style Vietnam style mags. You cannot use a anti-tilt follower as these are designed to tilt. If they have good springs, they generally work excellent. I have many thousands of rounds through these and never a jam. For curved 20 rd aluminum mags, they are just shortened 30 rd mags. You can use Magpul anti-tilt 30 rd followers in these curved mags, as its just a shorter 30 rd mag.

For Magpul mags, they sold a straight 20 originally. It was their least reliable magazine that they made/sold, so they went back to the drawing board, and designed the gen 3 20. This mag has a anti-tilt follower and a constant curve geometry. The gen 3 20 rd mag is probably the best built, best designed, and likely most reliable 20 rd mag on the market.

Lancer sells a straight 20 polymer mag. Its constant curve geometry inside and is a nice mag. They do have limiters built into them that make it hard to load 20 rds on a closed bolt. You need to shave this limiter down if you ever plan to load 20 rds into the mag. In fact, that applies to ALL Lancer mags, 20 or 30, they all have pointless limiters built into them that need shaved down. Magpul on the other hand designed their mags properly, which is allowing you the ability to load 1 or 2 extra rounds(dont load extra). This extra space is needed so that you can easily seat a full magazine on a closed bolt.

I have all the mags above. Both styles of metal, and both styles of Magpul. My favorite range mag is the straight aluminum Okay mag, like the original Vietnam style. They just work, and are excellent at the range. For defensive use, I would pick the Magpul gen 3. The magpul straight 20 is likely the worst of the bunch, but I keep them as they are collectible these days and sell for $40 to $50 each.

Everyone should have a few straight Okay 20's in their collection, excellent mags with lots of history and just cool.

Okay Surefeed AR-15 .223 Rem/5.56 20-Round Magazine
 
#20 ·
Everyone should have a few straight Okay 20's in their collection, excellent mags with lots of history and just cool.

Okay Surefeed AR-15 .223 Rem/5.56 20-Round Magazine
I keep meaning to pick up some Okay's. For the price, you can't complain. They're a few bucks cheaper than the M3 Magpuls and just as solid. Also, no issues when you get out the 75gr stuff or the heavy sub sonic Blackout loads.
 
#22 ·
I’m sitting in the hot tub. Your right, the Lancer 20’s are curved. I was going off memory.

As to Lancer limiters, I have about 30 of their mags and every one of them were way too stiff on a closed bolt due to the limiter. Consequently I shaved down the limiter in every Lancer mag I own. The limiter serves no purpose at all, it needs to go. The mags come out the other side better and easier to load on a closed bolt without the limiter. I would urge anyone to get rid of the limiters on their Lancer mags. I’ve never seen certain batch differences, all of the AWM mags from several years all appear identical.
 
#23 ·
^ :) Hey, we've all gotta our skin wet time, right? Hot tub is as good as any. :)

That's weird - do all your mags date from a certain time-period?

The ten 30-rd. L5AWMs that I actively use all date from 2014-ish. Four others reserved for HD use have also been vetted with loading to the full 30, and they were within this time-frame as well, in addition to a couple of 10-rounders and 20-rounders (both of which also load to full capacity, and can also be reliably inserted/locked bolt-forward on each of my ARs listed above). Of these, only the four HD mags are translucent smoked. All of the others are translucent clear.

I don't have any L5AWMs that pre-date 2012. I only started shooting as a hobby in literally the last months of 2010, and didn't start my AR journey until the second half of 2011. It wasn't until after I took my first real AR course that I started swapping my small cache of PMags for the L5AWMs, as my DD seems tolerance-stack with Gen M2 PMags, and seems to want to hang on to them a bit more.

I'm now tempted to start going into my stash of L5AWMs, and see if I can trace down a pattern! The prospect of having to load and unload all of them, though, kinda makes me not want to, even though it would be interesting! :D
 
#26 ·
^ I already have one. :) I use it to unload mags at the beginning of training classes if the instructional cadre asks for down-loaded mags. It's so much easier to do than stripping them out by-hand. Loading, I don't really find it to go any faster.

I actually don't find loading AR mags to be objectionable at all. :)

That said, I've wanted to get one of those loading trays........
There's always this.

MagPump PRO Mag Loader AR-15 223 Remington 5.56x45mm 300 AAC Blackout
 
#34 ·
In '65 I had a M-14, but I went back in '66-'67 (2nd Bn/3rd Inf, 199th Light Infantry Brigade) and had a original M-16. We did not use LBE (Load Bearing Equipment or Web Gear) for ammo pouches, all pouches at that time were for M-14 mags, you could put three M-16 mags in one, but it was kind of screwball as I recall.

M-16 ammo at the time came in regular metal ammo can with three bandoliers of seven twenty round boxes ( packaged as two ten round stripper clips) per bandolier. Usually there were two magazine loader adapters in each can. You placed the adapter on the empty magazine,, inserted a stripper clip, pushed the ammo into the mag, tossed the empty clip, put a second one in the adapter and down they go, remove the adapter, download two rounds to eighteen. that was Company SOP for a clean dry magazine.

The eighteen round download was so you could easily reload your rifle with a closed bolt, better than the magazine falling out when you acquired a target.

I used the now empty bandoliers to carry six loaded magazines, the middle bandolier pocket left open to rest better against your side. I carried three bandoliers of ammo and one of six frag grenades, if going on ambush from base camp I had second bandolier of grenades.

On return from whatever or base camp had cots so I sat on the cot and cleaned the rifle, taking it down to the bolt if it had been fired or not as were were in rice paddies and other wetlands. If fired I used solvent to clean then dry patches, finally wet patches of LSA (gun oil) and everything coated in gun oils and wiped down with a towel or Tee Shirt,

Then to the magazines, all nineteen. I took the liner out of my pot and stripped all the ammo into the pot. I then disassembled the magazines took a oily rag and a toothbrush, then a dry rag. Then a visual inspection, I rarely needed my bore brush. Once reassembled I tackled the old ammunition with the premise it may have been dunked, I wiped each round after inspection, with a oily rag and then dry one, re-inspected and then loaded one by one to the top and then down two rounds (Hard to keep count with everyone's activity and all) always interrupted for something. Replace any rounds tossed with new, stuffed the brushed bandoliers and I was ready Freddy.

All we had were twenty round magazines.
 
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