The History channel is showing the history of the M-16 (Modern Marvels) tonight at 10pm eastern and again at 2am(ouch!). I`m gonna have to tape it this time around.

That was excellent!  What a great documentary :)

Thanks for pointing that out!

E

Except that part about only putting 16 rounds in the 20-round mags so the springs don't wear out.  What's up with that?  I've heard of downloading the 30s by 2, but never the 20s.  

I have head of downloading the 20's to 18 rounds. I didn't think it was an issue with the spring wearing out, simply the mag being to tight.  I have had a 30 rounder (never 20's) loaded full up and the bolt would not move the top round to the chamber.  I since got rid of that mag. Although, I do download all my mags.
SugarD

I have got to record it this time.  Either that or just buy the tape.  I have missed it every single time!!!!!

There is no need to download 20's or 30's for reliable operation - unless you limp-wrist your reloads and don't whack them in place.

However it was common during Vietnam to download 20's by 2 rounds for two reasons:

1) ammo was packed in boxes of 20 - not on stripper clips - it was easy to overload by 1 (the mag will take 21 rounds) but putting 21 rounds in a 20 round magazine will Jam it bad!  So the SGT tells the men to load only 18 rounds - problem is solved even if you overload the 18 to 19 or 20 the magazine will function.

This was later solved by issuing ammo on stripper clips - then it was 2 clips per mag.

2) Sometimes soldiers would take the magazines apart to clean them.  Then when putting them back together they wouldn't install the spring correctly on the follower (it just needed to be barely on).  This would cause the magazine to only accept 18 rounds.

This was later cured by telling the soldiers only the Armorer should disassemble and clean the magazines insides - or if you did take one apart bring it to the armorer to fix.

Note many trainers still teach downloading by 2 for a couple of reasons:
1) that is how they learned so they 'continue the tradition'

or

2) its easier to insert the magazine (especially the 30) on a closed bolt if its downloaded.  Proper insertion followed by a strong Tap (WHACK!) on the bottom of the magazine should negate the need for downloading - but some still like the mag to click in place upon light insertion.

Was this the same as the "Tales of the Gun" episode about the AR-15/M-16?  I have that on tape.

I've not seen the "Tales of the Gun" M16 episode, but this was "Modern Marvels".

Loading 18 rounds in a 20 round mag not only improves the life of the spring it makes the guns easier to tac load and hence makes them more reliable.
PAT

I watched "Modern Marvels," and yes, it was the same show as "Tales of the Gun," with maybe a few minor edits/changes. It began with the black screen with white lettering... "the gun is part of history... etc." Good show. One of my favorite quotes from that show... "AK47s are favored by revolutionaries and the like because they can't afford M16s" That first AR15 was cute, the little 5 lb. rifle with a bakelite forend and pencil thin barrel.

BTW Glockfan, springs aren't worn out by static compression. They're worn out by lots and lots of loading (compression) and unloading (shooting - decompression) over time.

That was a really great program..  I taped it so that I can watch it again.

I've had a Colt SP-1 since the mid seventies.  I've always loaded 20 round mags with 20 rounds and 30 round mags with 30 rounds.  I have never had a single jam or failure to feed because of this.

A shooting buddy has an Auto-Ordnance semi-auto, long barrel version of the Thompson, along with a bunch of old beat up military surplus 30 round mags.  The old timers at the club told him to only load 28 rounds.  He ignored them and always loads 30 rounds.  He's never had a single problem doing this, and I'll bet he's fired 10,000 rounds through that gun in the last 20 years.

I sometimes wonder if these old "war stories" ever had a basis in fact, or if they got started by someone that just wanted to impress the girls at the USO.

If a magazine is designed and manufactured to hold 30 rounds, and loading it with 30 rounds causes a problem I would send it back to the manufacturer and have it repaired.

Thanks for posting this. I saw the show too, and thought it was great.

holeshot4

From my experience the main reasons to down load 20 round M16 mags to 18 rounds and Thompson mags from 30 to 28 rounds (or 20 rounders to 18) had little to do with the magazine or spring tension. Both guns were designed to be loaded with the bolts in the rear position; to let the top round position itself for loading (M16) or for firing (Thompson).  Original 20 round M16 mags , 30 and 20 round Thompson mags did not hold the bolt to the rear when the magazine was empty.  It was not uncommon in a firefight, when a magazine was loaded to its capacity, for the gun not to fire; because the magazine did not seat completely.  Upon recharging or cocking, the magazine would then fall out of the weapon.  This problem was later solved for the M16 when the 30 rounders were introduced.

All of my USGI 20-round mags will hold the bolt open on the last round.  The box they came in said they were made in 1971.  I've never heard of no-lock-open mags for an AR/M16.