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Discussion Starter #1 (Edited)
In another thread, the 30-round magazine was brought up and I thought now was as good a time as any to give a brief run-down on its development.

Initially the Army bought the M16 (XM16) with the simple 20-round magazine, and since that was what the M14 and T48 used, no further thought was given to the matter. Then in 1965, the Small Arms Weapons System evaluation was started with several weapons systems being evaluated. These were the M14/M60 combination, the Stoner 63 Weapons System, the AK-47/RPD/DPM combination, and Colt's M16A1 and Colt Automatic Rifle, basically, a heavy, removable barrel AR-15.

The Stoner 63, the AK and the Colt AR all used a 30-round magazine, and some of the evaluators started to think that a 30-round magazine in the M16 wasn't that bad an idea. But at the time there was no military requirement for a 30-round magazine, but if there ever where such a requirement in the future, the Colt AR magazine might be a good choice.

Increased usage of the M16 in combat in Vietnam resulted in a requirement for the 30-round magazine in mid to late 1966.

The Colt AR's 30-round magazine is a uniform curve magazine, very similar in profile to the Stoner 63 30 round magazine. It was thought that because the lower receiver of the Colt AR was the same as the M16 lower it would be a simple matter of inserting the Colt AR magazine in the M16. But things are never simple. Due to a wide variation of tolerance on the length of the M16's magazine well, some would indeed fit and work, but some would take a slight nose down attitude and snub rounds on the rear face of the barrel extension, and others just wouldn't fit. So the magazine was redesigned with a straight upper half and an increased curve on the lower half of the magazine, the profile we know today. In mid-1967 a prototype batch of the new profile 30-round magazines was tested in the M16 and CAR-15 (XM177), and found acceptable. A year later, a small pre-production lot of the new magazines was tested and the results were the same as the prototypes. Production started as soon as funding was available, but it wouldn't be until 1969 or 70 that the new 30-round magazine was commonly available.

In Vietnam, the XM177 is the M16 variant most commonly seen with the 30-round magazine as, I believe they were shipped with these. The 20-rounders remained in service until attrition and rotation of weapons out of service eventually saw the 20-round magazine phased out of service.

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The 30-round magazine is actually quite different from the 20-round magazine in terms of construction. The 20-rounders are made from a single piece of sheet aluminum folded to form the box and spot welded along the back, with a strip of sheet steel riveted to the front to prevent the bullets from denting the front wall under recoil. The front strip was found to be unnecessary, and the new design had right and left halves spot welded on both the front and back. There are also slight changes to the lip geometry, and the follower material was changed from cast aluminum to Nylon 6/6.

By the mid-1990s, with the introduction of the M4, the magazine when through another round of changes, all relating to the follower, first the green follower, then in the 2000s, the tan follower, both intended to reduce "follower-tilt" malfunctions. With the introduction of the M855A1 and the Marines' M27, further modifications were required to the lips to bring the nose of the bullet up and pointed more at the chamber. These were required due the exposed steel nose of the M855A1 hitting and scarring the aluminum portion of the feed ramp, and the fact the the rear face of the M27 barrel is flat, rather that the shallow cone of the M16 series.

The USMC seems to have opted out of this last change, preferring to go with Magpul Industries' PMAG M3. This actually marks the first standardized use of an all-plastic (save the spring) magazine in the US Military.
 

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Lysander,

You mentioned M855A1s, where any of the ammo released to the public, like seconds or rejects? I watched some gelatin tests, quite impressive. 100 % the tip separated, creating dual wound channel. I didn't realized before that behind that penetrator is solid copper alloy.
 

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The first 30 rd M16 mag I saw was in early April 1968 so it must have been one of the prototypes. A Captain in the Cav led a group of soldiers out to the 1/9 COC at the Rock Quarry at Khe Sanh and he had a 30 rd mag in his rifle. I was all set to liberate it when he left his rifle unattended but he came back too quickly. It was years before I saw another one.
 

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I saw a few 30 rnd mags used in conjunction with the CAR-15 by gents working with the ROK Marines and wearing the first Tiger Stiped Jungle uts I had seen in late 1967. We still had our M-14s at the time and joked about those guys with the toys. Had a chance to chat with one of the fellows and asked his opinion , his comment was " it's supposed to be better than our M-3s, but the jury is still out".
 

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The 1st 30 round mags, as mentioned by Lysander, were manufactured in the 1965 timeframe and were not reliable at all. They are one of the M16 collectors "Holy Grails". Referred to as "full curves". Very hard to find and very few were fielded for testing. Some reports say about 1,000 total were made. It is worth noting that these mags have stamped steel followers just like the 20rd "waffle" mags that came with the model 601 . I've had a total of 14 come thru my hands, some I've passed off to friends. Every one of them had a small dent/pinch mark across the front strap caused by the front edge of the lowers mag well. When inserted into the following lower receivers, some did fit "ok at best" some didn't, and too boot, example using the 64 SP1, some of the mags fit ok, some would not, so there may have also been slight variations in the mags themselves.
1964 Colt SP1
1978-79 SGW
1978 Palmetto Arms
Late 70s Sendra

Special Forces Major John Plaster, in one of his books, states something to the affect that in about 1968, 30 round mags were purchased out of "Guns and Ammo" magazine and sent to Nam, and used by some SF units. I do not know if these were the "full curve" mags, or the later version circa 1967-1969 type that has the straight top section.
These 67-69 mags will have either a very dark green or black plastic follower with a Colt part number (in white) visible from the top, they are not "anti-tilt" followers. They will also have a Colt part number stamped into the body.
Neither of these early 30 round mags were considered very reliable based on Military reports. The 2nd pattern was at best, acceptable. It was not until the anti-tilt followers were developed that the 30 rd mags became reliable.
My personal use (semi auto only, non combat conditions) of the 3 types gave me the same results..
 

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A few pics, the 4 on the left are "full curves", flash kinda washes out, but if you look close you can see the "pinch" marks between the 2nd and 3rd spot welds, they are worse then pics show,,, next 4 have the dark (emerald green) followers with part numbers on the follower and mag body. Last one on the right (old pic) is a "piggy back" experimental mag set. Pics loaded in reversed order, start at last one.
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Discussion Starter #7
The 1st 30 round mags, as mentioned by Lysander, were manufactured in the 1965 timeframe and were not reliable at all. They are one of the M16 collectors "Holy Grails". Referred to as "full curves". Very hard to find and very few were fielded for testing. Some reports say about 1,000 total were made. It is worth noting that these mags have stamped steel followers just like the 20rd "waffle" mags that came with the model 601 . I've had a total of 14 come thru my hands, some I've passed off to friends. Every one of them had a small dent/pinch mark across the front strap caused by the front edge of the lowers mag well. When inserted into the following lower receivers, some did fit "ok at best" some didn't, and too boot, example using the 64 SP1, some of the mags fit ok, some would not, so there may have also been slight variations in the mags themselves.
1964 Colt SP1
1978-79 SGW
1978 Palmetto Arms
Late 70s Sendra

Special Forces Major John Plaster, in one of his books, states something to the affect that in about 1968, 30 round mags were purchased out of "Guns and Ammo" magazine and sent to Nam, and used by some SF units. I do not know if these were the "full curve" mags, or the later version circa 1967-1969 type that has the straight top section.
These 67-69 mags will have either a very dark green or black plastic follower with a Colt part number (in white) visible from the top, they are not "anti-tilt" followers. They will also have a Colt part number stamped into the body.
Neither of these early 30 round mags were considered very reliable based on Military reports. The 2nd pattern was at best, acceptable. It was not until the anti-tilt followers were developed that the 30 rd mags became reliable.
My personal use (semi auto only, non combat conditions) of the 3 types gave me the same results..
Colt probably started production for civilian and export sale of 30-round magazines as soon as they felt the design worked. This was probably early 1967. The Army's slow, but normally methodical, approach to standardization is why there is a delay of two or three years before it starts being issued.

All of the "full curve" magazines are most likely part of the Colt Automatic Rifle production, which was very limited, as no one bought any in quantity.

The Colt AR as used in the SAWS evaluation:

 

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Discussion Starter #8
Just found a copy of Colt's drawing for the second pattern 30-round magazine (non-full curve, P/N 62328), and it's earlier than I thought. The drawing was drawn in March 1965.

This actually predates the SAWS test of the Colt AR. Colt must have known the full curve magazine design was marginal at the time of the test.

BTW, m1sniper, do your full curves have a part number on them?
 

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Lysander, " BTW, m1sniper, do your full curves have a part number on them? "
No markings on the outside, I have never removed the floorplate to examine the underside of the follower or the floorplate.
Interesting info regarding the type 2 mags. Thanks for that. I seem to remember reading in (maybe) "The Black Rifle" book by Blake Stevens that after the problems with the type 1 30 rd mags, Colt was slow to produce the type 2, and the military was not pushing for them.. So, the drawing, as per your findings show a 65 date, actual manufacture may have been later which certainly coincides with your info in post # 7. Known printed info from folks like Stevens say manufacture started in the 67 time frame.
There have been discussions on arfcom about the type 2 mags. A few examples have been posted with a .223 marked floorplate, most have the 5.56 marking.
With no way of actually proving a floorplate is factory original to a mag, I just wanted to thro that out as an FYI.
The 14 full curves I've had/have all have .223 marked floorplates, and again as mentioned, stamped steel followers similar to the 601 steel "waffle" mags..
 

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My Brother was stationed at Fort Lewis in the early 70's, He was a armorer, he said he started to see 30 round mags about 1973. He told me he once had to throw 2 full crates of brand new M14 mags in the trash because they weren't supposed to have them, I wish he could have made off with a couple dozen.

eQ
 

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There is so much waste that happens, it's a shame. I have a photo of a squad, taken June 1971, RVN, that shows the 30 round magazine in use in the field by regular infantry then.
 
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