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Posted: 10/29/2004 8:49:42 AM EST
Countless times I have read the history behind the development of the .223 55-gr and then the 62-gr round, but I can never remember which rifles/riflings work best with each round.

I am not concerned whether the rifles will function - I know they will - but I would like to know which of the 55-gr or the 62-gr works better, accuracy wise, with each of the following three rifles:

1. AR15 HBAR (1986 vintage)
2. H&K SL8-1
3. H&K HK93

Thanks!

Alex
Link Posted: 10/29/2004 8:59:02 AM EST
It all depends on twist ratio. If twist ratio is 1:12 or slower don't use anything heavier than 55gr.

www.ammo-oracle.com/
Link Posted: 10/29/2004 1:13:38 PM EST

Originally Posted By gotm4:
It all depends on twist ratio. If twist ratio is 1:12 or slower don't use anything heavier than 55gr.

www.ammo-oracle.com/



Huh?
Link Posted: 10/29/2004 1:59:13 PM EST
A longer heavier bullet(62gr or higher) needs to spin faster....1:7 twist rate or a 1:8 twist rate. If your guns have higher ratio(slower twist rates) barrels, use lighter bullets...(55gr).

What is the rifling in your guns?

The way to test it is to fire the heavier bullets and see if they keyhole when hitting a paper target at about 50-75yds. There should be a distinct indication of the yawing of the bullet. If this happens, use a shorter lighter bullet(55gr) and stick with it.

A longer heavier bullet is usually more accurate, but it must spin faster to be so.
Link Posted: 10/29/2004 2:26:40 PM EST

Originally Posted By alaman:

Originally Posted By gotm4:
It all depends on twist ratio. If twist ratio is 1:12 or slower don't use anything heavier than 55gr.

www.ammo-oracle.com



Huh?



Which words did you not understand?
Link Posted: 10/29/2004 3:27:05 PM EST
The Oracle says it's for less than 1-12 unless I read it wrong. 1/9 best
Link Posted: 10/31/2004 3:27:06 AM EST
What I have learned/asserted:

The H&K SL8-1 has a 1:7 twist rate, so it will be best with heavier bullets, 62-gr and higher.H&K - I have lots of this ammo.

But I am not sure of the twist rate of my 1986 vintage Colt AR15 HBAR. Any help?hanks!!
Alex
Link Posted: 10/31/2004 4:13:59 AM EST
On your Colt HBAR, look under the barrel between the bayo lug and the flash hider and you will probably see stamped the rifling that your barrel has. I would guess that you have a 1/9 twist with a Colt of that vintage.
Link Posted: 10/31/2004 5:19:38 AM EST

Originally Posted By alaman:
The Oracle says it's for less than 1-12 unless I read it wrong. 1/9 best




Less twist than 1:12 is usually 1:14, 55gr in 1:14 twist barrels will sometimes not stabilze in cold climates, this is why the M16-A1 had 1:12.

1:12 means that it takes 12" of rifled barrel for the bullet to rotate 1 full turn. 1:7 means 7" of rifled barrel and the bullet will rotate 1 full turn.

The US Military used 55gr ammo for many years in M16-A1 with 1:12 twist barrels with good success. Not until the adoption of the M16A2 by the USMC did the twist ratio go faster (to 1:7 twist) used to stabilze the long M856 tracer.
Link Posted: 10/31/2004 11:34:00 AM EST
Feel a bit like a fool... You see, a couple of days ago I looked 'under' the barrel of my AR15 thinking that is where any markings would be, but had found nothing, so I asked. I looked again just a minute ago, and sure enough - it has clearly stamped: "CMP .223 NATO 1/7 HBAR".

I apologize for taking your time.

Now I need to get some 62-gr ammo (surplus) for the AR and for the SL8. I have lots of 55-gr, but only the HK93 to shoot it.

Also, since I already reload .308, 30-06 and .45 ACP; I guess it's time to get some .223 dies and 69-gr or 75-gr ammo and start reloading them to see how well the rifles can really do.

Thanks to all!!!

Alex
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