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Been decades and just noticed ...


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#1 OFFLINE   AnOldBiker

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Posted Feb. 16 2017 - 11:29 AM

It's been decades since I shot an AR, but in the old'n days, we shot 5.56 NATO only, and when it left the barrel, after 66 feet it began to tumble. I know this for a fact since the targets showed round to slices in the holes.

 

Now with this new rifle I just bought, (granted I've only shot .223 through it so far), but every hole in the target is nice and round. No slices anymore.

 

When did they figure out why it tumbled and corrected this ?

Or did they ?

Is it just by shooting a .223 cartridge ?

Does the 5.56 still tumbles ?

 

 




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#2 OFFLINE   TomJefferson

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Posted Feb. 16 2017 - 11:38 AM

Its just a matter that there's better ammo and better barrels today and yes that goes for 5.56mm too.  

 

My rifle in the service was an M16E1.  I could write a book on strange things it did and none of my ARs do.  The old E1s didn't even have a brass defector.  That said, it punched nice holes.  There's a lot more attention paid to the crowns on barrels these days and a lot of those rifles we fired in the service had been abused a lot.  A lot of people believe tumbling was a myth these days but I personally think a lot of it was no rifling left or the crown had been dinged one time too many with steel cleaning rods.  Anyone who had fired night fire with tracers back in the day can tell you sometimes it did weird things.  Some of the guys i took basic with, I don't know how they qualified with the POS they had.   

 

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#3 OFFLINE   TackleberryMCS

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Posted Feb. 16 2017 - 04:24 PM

It's been decades since I shot an AR, but in the old'n days, we shot 5.56 NATO only, and when it left the barrel, after 66 feet it began to tumble. I know this for a fact since the targets showed round to slices in the holes.

 

Now with this new rifle I just bought, (granted I've only shot .223 through it so far), but every hole in the target is nice and round. No slices anymore.

 

When did they figure out why it tumbled and corrected this ?

Or did they ?

Is it just by shooting a .223 cartridge ?

Does the 5.56 still tumbles ?

 

 

 

How long ago has it been and which M16?

 

Some of the old Model 601s (early 1960s) has issues with tumbling because of the 1/14 twist rate. Even some of the early 1/12 twist barrels (late 601s and early Model 602s) had some issues as well, but it was ammo related. Most everything since 1966 has used improved ammo and has not incurred any tumbling issues. As long as it is 5.56 NATO 55 gr. ammo (M193), they shoot fine. I have several M16 clones with original Colt barrels and they all shoot very well with M193 ammo. 

 

Another thing that can cause tumbling is a worn barrel where the rifling has worn down not allowing the bullet to expand into the grooves, thereby causing it to loose velocity and stability since the bullet will not have enough spin being developed in the bore of the barrel.

 

As for the newer ARs, twist rates have changed resulting in a higher twist rate, thereby increasing stability over various bullet weights. 1/7 twist is the most popular as it can handle anything from 55 gr. to 77 gr. ammo. Then, there is 1/9 twist rate which is good for around 40 gr. to 72 gr. or 75. gr. ammo. There is also 1/8 twist which is good for anything from around 52 gr. to 77 gr. ammo. These higher twist rates stabilize these ranges of ammo very well out to various distances. 

 

One more thing. These days, you have .223 REM and 5.56 NATO ammo available. Generally, .223 REM is lower powered compared to the 5.56 NATO. You also have foreign-made steel-cased ammo that is also low powered. You seldom see or hear of problems with this ammo in regard to tumbling. As I said, the higher twist rates prevent this. You will have some ballistic changes depending on the ammo, barrel twist, and barrel length as far as accuracy over certain distances.




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#4 OFFLINE   bamashooter

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Posted Feb. 16 2017 - 05:19 PM

I heard the stories of the tumblers but my M16s  from 68-70 did not have that characteristic nor any AR-types since then.




#5 OFFLINE   prof_fate

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Posted Feb. 17 2017 - 09:55 AM

decades..define?

AR's originally at 1 in 12 twist and a tumbling bullet was sort of the idea. Geneva Convention only allows ball ammo, no hollow points. But a tumbling bullet will do more damage to the victim.
 

It's been decades since I shot an AR, but in the old'n days, we shot 5.56 NATO only, and when it left the barrel, after 66 feet it began to tumble. I know this for a fact since the targets showed round to slices in the holes.

 

Now with this new rifle I just bought, (granted I've only shot .223 through it so far), but every hole in the target is nice and round. No slices anymore.

 

When did they figure out why it tumbled and corrected this ?

Or did they ?

Is it just by shooting a .223 cartridge ?

Does the 5.56 still tumbles ?

 

 




#6 OFFLINE   TomJefferson

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Posted Feb. 17 2017 - 11:44 AM

BTW guys just so you know, I flat out loved the old 1:14 20" barrels.  Man, would it sling a 55 grain pill out there.  You could pop a half silhouette all day long out to 650m.  My M16 in basic would bend a round double on full auto but man, could it thread a needle.  If I recall, they speeded it up because of cold weather firing.  


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#7 OFFLINE   TackleberryMCS

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Posted Feb. 17 2017 - 12:15 PM

BTW guys just so you know, I flat out loved the old 1:14 20" barrels.  Man, would it sling a 55 grain pill out there.  You could pop a half silhouette all day long out to 650m.  My M16 in basic would bend a round double on full auto but man, could it thread a needle.  If I recall, they speeded it up because of cold weather firing.  

 

 

While the standard 1/14 .224 barrel twist was quite successful in commercial firearms it did not serve the AR-15 well. M193 ammunition utilizes a boat tail projectile rather then the more common flat base. Boat tail bullets have less bearing surface to engage the rifling of the bore then flat base bullets of the same weight. The result was that the 55 grain FMJBT bullets were on the edge of stability when fired from the AR-15. Accuracy testing conducted by the US Army, US Air Force, and the NRA showed unacceptable accuracy with the 1/14 twist. Because of these factors a twist change to 1/12 was approved on July 26th, 1963.
 

 

In 1964, the Army was informed that Dupont could not mass-produce the IMR 4475 stick powder to the specifications demanded by the M16. Therefore, Olin Mathieson Company provided a high-performance ball propellant. While the Olin WC 846 powder achieved the desired 3,300 ft (1,000 m) per second muzzle velocity, it produced much more fouling, that quickly jammed the M16s action (unless the rifle was cleaned well and often).




#8 OFFLINE   AnOldBiker

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Posted Feb. 17 2017 - 01:11 PM

1st one I had handed to me in Nam was a M16A1. It was brand new, we cleaned and they gave us 3 mags full of 5.56. We zeroed and shot the rest in semi and auto to confirm working properly, cleaned and went to the field. The Armor NCO was to send back the damaged ones we brought out to replace. I looked at the targets we shot at to zero them in and that's when I confirmed they tumbled. Every target proved it. They traveled straight, but the holes were every kind of hole you could imagine. Had it for 1 1/2 months until I was ordered to carry the M60 when the squad gunner was injured. (Don't be the larger person when weapon reassignment happens in the field)

 

After zeroing in this new AR, I was stumped when every hole was so perfectly round. But I have been shooting the .223 for now, saving some cash at the range.

I was wondering about all this .. thanks for the info. 


Edited by AnOldBiker, Feb. 17 2017 - 01:13 PM.



#9 OFFLINE   TackleberryMCS

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Posted Feb. 17 2017 - 01:34 PM



1st one I had handed to me in Nam was a M16A1. It was brand new, we cleaned and they gave us 3 mags full of 5.56. We zeroed and shot the rest in semi and auto to confirm working properly, cleaned and went to the field. The Armor NCO was to send back the damaged ones we brought out to replace. I looked at the targets we shot at to zero them in and that's when I confirmed they tumbled. Every target proved it. They traveled straight, but the holes were every kind of hole you could imagine. Had it for 1 1/2 months until I was ordered to carry the M60 when the squad gunner was injured. (Don't be the larger person when weapon reassignment happens in the field)

 

After zeroing in this new AR, I was stumped when every hole was so perfectly round. But I have been shooting the .223 for now, saving some cash at the range.

I was wondering about all this .. thanks for the info. 

 

Did it have the old 3-prong FH and D type stock (no trap door) or the birdcage FH and E type stock (trap door)? The reason I ask is because the early M16A1 (1967-1971, no forge codes on the carrying handle) had the old 3-prong FH and D type stock (carry-over from the XM16E1). Some of these had the 3-prong removed and a birdcage FH installed. The later M16A1 (1972 -1982, CK, CH, and some CM forge codes) came with the E type stocks and birdcage FHs.

 

 I am kind of an early M16 aficionado is why I am asking.

 

003_zps2jfn172w.jpg


Edited by TackleberryMCS, Feb. 17 2017 - 01:39 PM.



#10 OFFLINE   AnOldBiker

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Posted Feb. 17 2017 - 01:50 PM

 

Did it have the old 3-prong FH and D type stock (no trap door) or the birdcage FH and E type stock (trap door)? The reason I ask is because the early M16A1 (1967-1971, no forge codes on the carrying handle) had the old 3-prong FH and D type stock (carry-over from the XM16E1). Some of these had the 3-prong removed and a birdcage FH installed. The later M16A1 (1972 -1982, CK, CH, and some CM forge codes) came with the E type stocks and birdcage FHs.

 

 I am kind of an early M16 aficionado is why I am asking.

 

003_zps2jfn172w.jpg

 

 

 

I was there in 70-71.  

We were informed we had the 'new' design barrel and the 'new' forward assist for the bolt.

Since I left country, all I've handled for 42+ years was my old Remington 30-06.

Just got the bug again for something new .. at the end of last year.

Sorry, not much help.


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#11 OFFLINE   TackleberryMCS

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Posted Feb. 17 2017 - 02:04 PM



 

 

 

I was there in 70-71.  

We were informed we had the 'new' design barrel and the 'new' forward assist for the bolt.

Since I left country, all I've handled for 42+ years was my old Remington 30-06.

Just got the bug again for something new .. at the end of last year.

Sorry, not much help.

 

I have a couple Remington .30-06s myself.

 

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#12 OFFLINE   Blacktree

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Posted Feb. 17 2017 - 02:37 PM

During my entire time in the service, I never saw an M16A2 tumble a round. So it must be an early M16 thing.




#13 ONLINE   Srgt. Hulka

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Posted Feb. 17 2017 - 03:44 PM

Did it have the old 3-prong FH and D type stock (no trap door) or the birdcage FH and E type stock (trap door)? The reason I ask is because the early M16A1 (1967-1971, no forge codes on the carrying handle) had the old 3-prong FH and D type stock (carry-over from the XM16E1). Some of these had the 3-prong removed and a birdcage FH installed. The later M16A1 (1972 -1982, CK, CH, and some CM forge codes) came with the E type stocks and birdcage FHs.
 
 I am kind of an early M16 aficionado is why I am asking.
 
003_zps2jfn172w.jpg


Dang it Tack! Those are purty! One day I'll have one in my safe.
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#14 OFFLINE   TackleberryMCS

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Posted Feb. 17 2017 - 07:24 PM

Dang it Tack! Those are purty! One day I'll have one in my safe.

 

I am working on another M16A1 clone (circa 1972-1973) right now. The upper assembly is already complete. I just have to wait a few more months for the lower from Nodak Spud to finish the lower assembly. I have another M16A1 clone from the same era already built.







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