Loads for an 1:12 M16A1 Upper?


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Blind Bat
January 10, 2009, 10:38 AM
I built my first AR lower last summer and was planning to order a CMMG mid-length 16" upper for it on my birthday but due to Obama-mania I probably wouldn't see any new upper before April. I found an unfired Colt M16A1 upper still in cosmoline and decided to build an Vietnam era tribute riffle instead.

This will be my first attempt at reloading .223 so I don't have any supplies yet. Can anyone suggest a good load for a 20" 1:12 twist 5.56/.223 upper? I prefer clean and accurate to fast and powerful. I use an RCBS Uniflow powder measure. Thanks once again.


P.S. I'm leaning towards W748 because rcmodel is my hero. :)

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rcmodel
January 10, 2009, 12:52 PM
26.3 grains WW748 and any good quality 55 grain bullet.

That rules out FMJ bullets if best accuracy is required.

rc

Ben Shepherd
January 10, 2009, 12:55 PM
Clean and accurate in a 1:12 barrel you say? Look at vit powders(expensive but VERY clean), and any high quality slug between 40 and 55 grains. One in 12 is too slow for anything heavier as a general rule.

tkcomer
January 10, 2009, 01:17 PM
Can't really tell ya what powder charge to use as you didn't mention bullet weight, but I've had good luck with Winchester 748 and Ramshot Tac out of my 1:12 M-16 and AR-15. Meters great through my Uniflow.

Blind Bat
January 11, 2009, 12:03 AM
you didn't mention bullet weight

I was planning to use a 50-55gr bullet but I was overwhelmed by the shear number of options for this caliber.

rc - Is it the lead base exposed to the burning powder that causes accuracy problems with FMJ bullets in .223? Do hollow point .223 bullets have an exposed base or should I stick with a soft point bullet?

How do these (http://www.midwayusa.com/eproductpage.exe/showproduct?saleitemid=324450) look? They appear to be one of about four 55gr, non-fmj bullet in-stock at Midway and they are quite a bit cheaper than everything else...


Thanks!

rcmodel
January 11, 2009, 12:26 PM
FMJ bullets are the only type that has an exposed base, because the tip is closed.

If the tip is open (SP, HP, B-T, etc.) the base is always closed.

The problem with FMJ is not that the base is exposed to burning powder.
The problem is that it is very difficult to make every bullet base exactly flat. The excess jacket is squeezed out the rear of the bullet swaging die, and more jacket may end up on one side then the other.

Then, as the bullet exits the muzzle, more powder blast happens sooner on one side of the bullet base then the other. That results in tipping, and a wobbling flight until the bullet can eventually right itself and fly right.

Closed base bullets don't have this problem because every one is exactly flat and uniform.
If the tip is slightly uneven, it has almost no effect on the bullet flight compared to an uneven base.

The other thing is that most FMJ bullets are made on military production lines with military acceptance standards. (which are lower then commercial bullet standards) There might be 10 - 20 machines making the same bullets, which are all dumped together for finishing & packaging.
Out of 100 bullets, you might get 16 out of one die, 13 out of another die, 23 out of yet another, and so on. So consistancy is just not there.

rc

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