[wanderinwalker]

I am aware that the .223 is fairly twist-rate sensitive with regards to bullet selection. My current rifle has a 1:8" twist, I believe. So will this stabilize 80gr bullets? 77s? Just curious. Thanks.

[P95Carry]

walker - opinion seems to vary but ... IMO 1:9 will do fine for up to 55grn but my Mini-14, at 1:7 is well able to handle 68grn and over.

1:8? ... well probably might be OK for 68's but as to heavier ...... I rather think perhaps not .... see what others say. 80 region is pretty damn heavy for the cal too!

BTW ... easy way to check twist in case some not tried it ..... put a brass jag on end of cleaning rod and twist on a patch...... push down bore to near chamber. Mark rod across and along to make a cross.

Withraw rod until that cross is again at top showing a 360º revolution and re-mark across.

Measure distance between the two marks made across .. that's the inches of twist for the one full turn.

[cookhj]

when the army went to the M-16 as their competition rifle for service rifle competition, they used a bunch of CAD/CAM programs (computer aided design/computer aided manufacturing) to find the optimal dimentions for the rifle. they found that for the 69 gr and 80 gr sierra bullets, a 1:7.775" twist was optimal. however, there is only one company that i know of that makes barrels in 1:7.775" and i think that's obermeyer. however, a 1:8" twist is close enough to 1:7.775" that it shouldn't make too much of a difference. just my $0.02.

[Zak Smith]

According to JP, who builds rifles for 3Gun, 1:8 is perfect for the 75 and 77gr bullets. (Edit: they didn't mention 1:7.7 at all.) 68/69's are okay in 1:8 too.

1:9 will easily stabilize 68's and 69's.

Hornady claims that the 75gr HPBT will stabilize from a 1:9 barrel. Results have been mixed. The 75/77's were less accurate than the 68/69's in my 1:9 Rock River.

-z

[Quintin Likely]

1:9 twists will stabilize anything up to around 75 gr. or so, although the 69s work much better, at least they do for me, granted all my shooting is at 100 yards while I'm trying to figure out the science of going way out there.

I *think* the 1:8 twist will stabilize the 77 or 80 gr. Matchkings, I'm sure some of the highpower AR shooters around here can verify this or not.

[wanderinwalker]

Thanks all. I guessed that the Armalite will handle 77s and 80s adequately, but I guess I'll just HAVE to go try it out and see. :rolleyes: The idea being, when I get to play over at the 600 yard range, I want to get the most out of my AR and my scores. Not sure if the 69s will cut it that far away (I know they work fine to 300). Again, thanks.

[cookhj]

69's will work fine at 600 AS LONG AS there's very little wind.

the 80's should do just fine.

[SteelyDan]

Gees, they're making 80-grain bullets now?? Why do these things keep getting heavier? I'm actually serious. I thought the whole point of the 55-grain, or even 62-grain, 5.56s was that the velocity allowed them to fragment? As far as I know, for 40 years the bullets remained about the same size. But lately, they're just getting bigger and bigger. How effective are these things?

Anyway, check out the sticky posts at the top of this page:

http://www.ar15.com/forums/forum.html?b=3&f=16

There is likely something helpful there, though I can't recall reading about 80-grains. I mean, what's next, 165-grain .223s??

[Zak Smith]

Check out http://www.ammo-oracle.com

The 68, 69, 75, 77, and even 100gr .224" projectiles are even more "terminally effective" than 62gr M855 or 55gr M193. Instead of requiring 2700fps or greater to fragment, they do it down to 2000-2200fps.

-z

[Sleeping Dog]

SteelyDan, no the purpose of the 80-grain bullets is not to fragment, it's to punch holes in paper (or prairie dogs) at rediculously long distances.

It is certainly not a battle bullet. The rounds made from 80-grain bullets won't even fit in a magazine, they have to be single-loaded. That's why someone makes special mag followers that make single-loading easy. You need the single-load ease and speed to make it though the rapid-fire segments of a match.

1:8 twist will stabilize the 80-grain bullet.

Regards.

[wanderinwalker]

Sleeping Dog,
For the rapid fire sets, everybody I've ever shot with uses mag-length rounds with either 69s or 77s. The 80s, AFAIK, are STRICTLY for the 600 yard prone slow-fire stretch.

Thanks everyone for your input. No, I'm not worried about terminal effect! I want maximum points when I start shooting out-there. After seeing what a stiff wind will do to .30s from 300, I figure I can use all of the help I can get!

[Steve Smith]

Post edited by self in order to be more civil.

Walker, yes, 1:8" twist barrel will stabilize a Sierra MK 80. A 1:9" MAY stabilize a 75 or 77 grain. The problem arises when a company thinks they are cutting at a particular twist but their rifling cutter or button is slower than they thought. Some folks wind up with fast 1:9s and others have slow ones. I don't think I've heard of slow 1:8s but I know there are "fast" and "slow" 1:9s because I have seen it.


I have a 1:6.5 coming for my next comp gun, and I'll shoot 90 grain JLKs in it.


Oh, and Walker, use 77s at the short distances. You don't have to, but I do.


Steely, WanderinWalker is just starting in a competition called NRA Highpower Rifle, a discipline that I am very involved with. We shot AR-15 and M-14 rifles at 200, 300, and 600 yards from field positions with iron sights. Some of us push those mouseguns to 1000 yards quite well. The heavier (and better ballistically) the bullet is the more speed you retain over the distance, and the less wind drift you have. FWIW, I would not want to be downrange of any Highpower shooter who is proficient in his long game...even if he "just" has an AR.

[cookhj]

not to get off topic, but who makes the 80gr and 100gr bullets? i thought that the 100gr bullets were still "under development."

[Steve Smith]

80s are built by several companies, Sierra being the most popular. I don't remember whos is building 100s but it is IMPERATIVE to note that they are not match bullets and do not have a high BC. They are for fighting, not accuracy.

[wanderinwalker]

Mr. Smith,
Forgive me my ignorance, but what exactly are these "JLKs?" I've noticed you speaking of them before, and am curious, is all.

And once again, many, many thanks to all.

[Steve Smith]

JLK...made my Jimmy Carlene Knox. They are a VLD design (Very Low Drag) similar but wiith different angles to the Berger VLD.


Nothing for you to fuss with yet...stick with Sierra MKs for now. Learn to shoot those well and then experiment.



Here is a reasonably good article on heavy .224 bullets. It should have ended with this statement: "Now the question is not 'How well does it shoot at 600' but rather 'How much better does it do at 600?" http://www.gun-tests.com/newspics/pdfs/1-1-Bullets.pdf

[wanderinwalker]

Re: the JLKs. Oh no, I don't want to fuss with that kind of stuff yet. But it feels like sitting in on a Biology lecture and not knowing what DNA and RNA stand for. I fully plan on burning out two or three barrels before I start to REALLY fuss! :)

[cookhj]

i don't know why i asked who makes 80 gr bullets.

i meant 90 gr bullets.

i thought that someone was supposed to be making a 100 gr .224 bullet for competition that had a powdered tungsten core for match use out beyond 600 yds.

[makarov]

In my CZ-527 which has a 1:9 I have found the 55 grainers are still more accurate than the 62 or 69. It actually works even better with 40 grain bullets.

You need to shoot a variety of weights and bullets from your gun to see what your barrel *likes*.

Mine does pretty well with the S&B .55's and even the cheap UMC 55's.

- Makarov

[Nero Steptoe]

Beware of advice regarding accuracy from a guy who uses "Mini-14" in his post! ;)

[P95Carry]

Beware of advice regarding accuracy from a guy who uses "Mini-14" in his post! Nero - I resemble that remark!!:D

Anyways ... all is relative ... some things still shoot ''better'' out of a Mini than others!!:neener:

[wanderinwalker]

makarov,
Yeah, the 55s still shoot alright, but I have a hard time when the wind pushes them like a curve ball. More mass=less drift.