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-   -   Low 223 velocity. (http://www.calguns.net/calgunforum/showthread.php?t=652062)

mkga14 12-03-2012 3:47 PM

Low 223 velocity.
 
Good evening Calgunners!

With my recent purchase of a chrony... I have more questions!

ATM I am shooting my reloads through a 14.5 inch 1x7 twist barrel. Reloads are made from once fired LC brass mixed with some PMC 223 pick ups. Sized and trimmed to spec, loaded with 22.7 gr of H335 shooting a 55 gr Hornady FMJ-BT w/c.

I set my chrony about 10 feet away, like the instructions says, shot about 30 rds through it and i'm seeing an average of 2430-2460 fps. In the Hornady reloading manual, it lists 22.5 gr of H335 at 2500 fps.

At the moment I'm just paper punching and attempting to hit some steel targets at 600 and below. So the low fps isn't that big of a deal to me. I've seen around 3100 fps out of factory XM193 rounds. My question is... How can I get that far if the max in the Hornady manual is listed at 23.5 gr at 2600 fps?

I realize factory XM193 rounds don't use H335. Has anyone loaded H335 up to 3100 fps? If I ever wanted to load up to that, should I just keep adding powder in .1/.2 increments until I see signs of over pressure? Ejector snare, popped primers and craters. Seems a bit dangerous to me but I'm stupid enough to try! :oji:

On a side note, the manual also shows 23.2 gr of H335 at 3100 fps BUT that's out of a 26" 1x12 twist barrel.

Sorry for the newb question, and thanks in advance!

bohoki 12-03-2012 3:58 PM

i doubt you could ever get 3100 with only 23.2

rsrocket1 12-03-2012 4:06 PM

600 yards with a 14.5" barrel?
With a 2500 fps MV, you'll need a 163" hold over. My typical load is 25.0g H335 which gets me ~3000-3030 fps out of a 20" AR

I would not exceed the recommended max load. A 3100 fps 26" MV translates to a MV of 2800 fps with a 14.5" barrel.

mkga14 12-03-2012 4:19 PM

Yeah no wonder why I could never hit those. Best I could ever do were the 300s =]

Well, if I could only get 2800 fps out of the max load... then I'll settle for that! Or buy more xm193 but that would defeat the purpose of reloading!

Thanks for your help!

ptmn 12-03-2012 4:43 PM

One of the reasons why you are getting more velocity out of M193 is because it is loaded to higher pressure than the .223 load data that you are pulling from your reloading manual. Higher pressure of the military loading equals higher velocity. I have an excerpt from an article regardign the pressure difference between SAAMI vs Military M193 loadings:
The 5.56 mm NATO and .223 Remington cartridges and chamberings are similar but not identical. Military 5.5645mm cases are often made thicker and therefore have less case capacity.[26] However, the NATO specification allows a higher chamber pressure. NATO EPVAT test barrels made for 5.56 mm NATO measure chamber pressure at the case mouth, as opposed to the location used by the United States civil standards organization SAAMI. The piezoelectric sensors or transducers NATO and SAAMI use to conduct the actual pressure measurements also differ. This difference in measurement method accounts for upwards of 20,000 psi (140 MPa) difference in pressure measurements. This means the NATO EPVAT maximum service pressure of 430 MPa (62,000 psi) for 5.56 mm NATO, is reduced by SAAMI to 55,000 psi (380 MPa) for .223 Remington.[27] In contrast to SAAMI, the other main civil standards organization C.I.P. defines the maximum service and proof test pressures of the .223 Remington cartridge equal to the 5.56 mm NATO.

rsrocket1 12-03-2012 5:49 PM

Just think about it, your 14.5" is made for close quarters combat, not exchanging sniper fire from hilltop to hilltop.

If you want long range at least go with a heavier bullet. A 75g bullet might only be loaded to about 21g of H335 and will have a MV of 2450 fps but will drop only 120" @ 600 yards. Heavier bullets will drop less than light ones when you get into those long distances. They are also less prone to wind drift.

mkga14 12-03-2012 6:13 PM

Hmmm, you're right. I should be happy with hitting the 300 plates. Perhaps a longer barrel/upper will do. Thanks again.

mif_slim 12-03-2012 6:40 PM

Jist remember that the books mostly will publish loads with its optimum ability. Most will be 24-26" barrel for .223/5.56. These numbers gets new reloaders excited until they get results and its not the same.

2450Fps is just right. I get about 2535fps with my 16" and 2900 with my 24".

tiller 12-03-2012 7:06 PM

Your way under minimum... Ithink the hornady book is 23.5 grains min...

I use 24.5 for a plinking round

bigdawg86 12-03-2012 7:46 PM

It's hard to see a blazing hot FPS but not be able to reproduce it... I was averaging 2975+/- FPS with my 16" barrel / 55g FMJ and it was killing me not to hit 3000.

I laughed when I was seeing 24" barrel lengths used with certain powder website data.
With a barrel that big you might as well be jousting your opponent on a horse.

bloodhawke83 12-03-2012 8:38 PM

http://data.hodgdon.com/cartridge_load.asp

book says 22.3grs with a 26" barrel, you'll lose about 50 fps per inch? :shrug:

CGT80 12-03-2012 11:43 PM

23.2 of H-335 gives me 2949 fps average and a high of 3041 fps. This is the most accurate load I have tried in my Mini 14 Target model that is chambered for 223 Rem. and has a 1:9 twist and 22" barrel.

24.0 grains of H-335 gives 3011 fps average and 3106 fps high. This load doesn't group as well as the lighter one.

I use a berrys/hornady 55 fmjbt and mixed brass. Other people with shorter, 5.56 chambered, AR15's report lower velocities than what I got as well.

Wrangler John 12-03-2012 11:48 PM

Your rifle has a 1/2" shorter barrel than my Contender pistol in .223 Remington. That's all the velocity it's going to produce.

Trash 12-05-2012 7:44 AM

Quote:

Originally Posted by rsrocket1 (Post 9845075)
A 75g bullet might only be loaded to about 21g of H335 and will have a MV of 2450 fps but will drop only 120" @ 600 yards. Heavier bullets will drop less than light ones when you get into those long distances.

I think what you meant to was that heavier bullets are more stable and predictable at long ranges. Drop is a function of time of flight and NOT bullet weight. A slower bullet will drop more over a given distance than a faster one.

GeoffLinder 12-05-2012 7:53 AM

Quote:

Originally Posted by Trash (Post 9855815)
I think what you meant to was that heavier bullets are more stable and predictable at long ranges. Drop is a function of time of flight and NOT bullet weight. A slower bullet will drop more over a given distance than a faster one.

This ^^

The reason for using heavier bullets is lower drag so less drop percentage is realized than lighter bullets (not less drop overall, just less of a percentage than lighter with velocity difference factored). Lower drag and VLD profile also contribute to less wind drift.


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