The Down Range Forum
Member Section => Tactical Rifle & Carbine => Topic started by: fullautovalmet76 on October 02, 2008, 09:52:02 PM
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I sometimes buy ammo from the Ammoman.com. The site advertises ammo in 5.56 that is green tipped. I don't know what that is supposed to mean. Would someone clue me in, please?
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Read this
http://www.thegunzone.com/556faq.html
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I sometimes buy ammo from the Ammoman.com. The site advertises ammo in 5.56 that is green tipped. I don't know what that is supposed to mean. Would someone clue me in, please?
I believe that green tip is the M855 ammo, with the SS109 bullet, which has a steel penetrator core. Usually more expensive than the "normal" plinker ammo, usually flagged M193 (IIRC).
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Thanks for the link, Hazcat! It completely answered my question.
-G
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We but exist to serve. ;D
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For anyone who doesn't want to read the whole article:
Regular ball ammo is plain with no paint.
Armor piercing ammo is black tipped.
M855/SS109 is green tipped because it as a hybrid ball with penetrator.
As far as I know there aren't any other calibers with green tips.
The bullets will actually stick to a magnet but not really well.
Some people selling it advertise it as armor piercing ammo but it's not.
You can also get ammo with the same bullet weight without a penetrator.
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I do have one other question. According to the article the round is designed for barrels with a 1:7 twist; my barrel has a 1:9 twist. Given this, will the round still perform with a reasonable degree accuracy? Instead of getting 1 or 2 MOA at 100 yds., will I hit something on the planet Jupiter instead? ;)
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That bullet and similar weights will work GREAT in a 1:9 twist. The 1:7 is designed for the (extra long) tracer bullets. There's some argument about whether or not it was even neccesary for them. Winchester 64-grain PSP should work if you want to shoot game up to deer size.
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JumboFrank,
I thought it might work, but I wanted to consult more experienced shooters with this type of rifle on this one...Thanks again!
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I copied this from www.cactustactical.com/reloading/tips2.doc
Long Range Shooting Secrets
Bullets Tips
Rifle Twist Rates
.223 / 5.56mm
1:14 up to 55 grains
1:12 55 – 63 grains
1:9 63 – 70 grains
1:8 70 grains or more
It not that clearly defined in real life. For 62 grain bullets I'd still take a 1:9 over a 1:12 no matter what they say. A barrel in with a twist in between those two like a 1:10.5 would be even better, but I'm not buying a custom barrel. I shoot 55 grain bullets out of the fast 1:7 and 1:9 twists because those are the barrels I have and 55 grain ammo is cheaper. It just won't have great accuracy because it's over-stabilized.
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Interesting stuff. So for accuracy of a 16in. AR-15/M4 barrel what would you guys recommend? 62Gr., 64Gr., 69Gr. Hp/ FMJ/SP ? I am curious because I have a friend that says he gets "big groups", from his AR with a 16in. barrel, using only 55gr fmj bullets. Could this Grain weight throw off his groups that much? His gun's barrel is stamped 5.56 too btw. Any thoughts?
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What is the twist rate?
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What is the twist rate?
Yeah that might help huh? ::) His is a 1-9 twist, 16in., 5.56mm chrome-lined barrel. He has mostly shot 55Gr. and a box of 60Gr., which seemed a little better. So, perhaps 62Gr.-69Gr. might work better. Thoughts?
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I'm still learning myself, but from what I've been told the slower twist would be better with lighter bullets. I have a 1 in 9" and shoot mostly 55 gr right now. I want to go up to 69 gr or 72 gr for the longer range, but long range shooters are telling me that 69 gr is really pushing the limits of 1 in 9". They recommend 1 in 8" and to use it with nothing lighter than 55gr. One "expert" told me a 52 gr through a 1 in 7" won't even hit paper consistantly ... don't know.
My barrel length is 20", most long range guys I talk to are using 20" to 24 inch (most common) with some a couple at 18".
I have shot one box of 69 gr through mine, and it did better at 400 yds than they 55 gr, but it was a matter of a larger group with heavy vs drift on the lighter. Seems to verify that the heavier bullet needs faster twist to stabilize. Not sure if barrel length is for twist or full powder burn.
Short version:
I've been told the lighter the bullet the slower the twist, and there is a lot of disagreement of where the need to go from 1 in 9" to 1 in 8" is.
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I think you need to experiment for yourself to find the best bullet weight, and the chart from cactustactical is a good starting point. Something else to consider when getting an M4 contour barrel is that the M203 mounting groove is a weak spot that may cause excessive vibrations between the front sight and muzzle, and may give less accuracy than a "solid" 16" barrel. I haven't seen any real data yet, just hearsay.
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Excellent post Hazcat. The history about the ammo and rifle was good, but I learned a bit about the different types and distinction of the specific rounds. Great article
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longer bullets typically have a higher ballistic coefficient... how well the bullet moves through the air without deflection... the heavier bullets will have less wind deflection than lighter bullets... my game gun has a Rock River free floated chrome lined 16" mid, with 1/9 twist... it has an affinity for S&B 55grain M193... and will shoot 5 shot groups into 4" at 400m... hand loaded Sierra 69 grain bullets will shoot the same, but will have 1/2 the wind deflection....
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Regarding rifling twist and over stabilization.
There are a lot of interesting articles on this subject, but unless you are shooting a very light for twist bullet, 40-50 grain in 1-7, 1-9,
you would not see any dramatic problems unless you are shooting over 200 yards.
At those ranges most shooters can't shoot a .223 that well, unless the rifle is set up for it.
For long range (300 yards) squirrel shooting, I shoot a 22-250 at 3600 fps, with a 53 grain HPFB in a heavy 26" barrel. This bullet is a Sierra bench rest bullet. The rifle is a 1-12 twist. I have shot 45 grain weight bullets, at over 3800 fps, and could not put holes in a target at 100 yards. Why? We observed that there was a smoke trail to the target, but no hole. You could not do that with a .223, because you could not get enough powder in the case. The assumption is excessive spin for a light bullet caused by very high velocity for that bullet.
Yes, you can over stab a bullet with light bullets and a excessive twist, but it is much more common to go the other way, heavy bullets with slower twist.