Greenhill Formula and .223 Remington

[Das Capitolin]

For those familiar with the Greenhill Formula, I'm trying to confirm the ideal .223 Remington bullet length for a 1:9 twist 20" barrel AR15. The best length (L) I've found to hit a perfect 1:9 twist rate is a 0.8362" long bullet.

Using the formula, I've got a bullet diameter (D) of .224 divided by length variable L (.8362), which is then divided into 150 and multiplied by D. This gives me near-exact 1:9.

Now the questions: are there .8362 long .223 Remington bullets available? Expert advice needed.

 

[Das Capitolin]

Re: Greenhill Formula and .223 Remington

I should add that what I'm really after is a set of particular grain/bullet brand/type that will most closely match .836 bullet length. I'm also concerned how BTHP might impact Greenhill's formula.

 

[Mordamer]

Re: Greenhill Formula and .223 Remington

I'll go measure some of my bullets and see which ones are the closest to that length. Might I ask why you are trying to stick to that formula so closely? There is nothing magical about the formula that will make a bullet of that length work perfectly.

 

[Mordamer]

Re: Greenhill Formula and .223 Remington

The Sierra 69 grain HPBT bullets I have average about .887". Those bullets shoot ridiculously well out of just about any 1:9 twist gun. I just happen to have a box of the new 53 grain Vmax bullets from hornady. They average just about .830". They are nice bullets for shooting varmints and have a surprisingly high ballistic coefficient for being so small. I still don't understand why you are looking for a bullet of this length, but glad I could help.

Those are the two closest bullets I have to that length and I have a plethora of .223 bullets. The only heavy bullets that are going to be close to that short are the Sierra 69 grain HPBT's.

 

[Das Capitolin]

Re: Greenhill Formula and .223 Remington

I don't have any bullet software, nor do I know where to find any/what to use. Like I said, advice is welcome. If someone has suggestsion, especially links to free software, I'd be thankful!

 

[Mordamer]

Re: Greenhill Formula and .223 Remington

What exactly are you trying to find out? Are you new to reloading and want to find a load that will shoot well in your gun? Do you want to shoot long range targets/varmints, or shoot close range (within 300 yards), or something else? I shoot a 1:9 twist .223 with a 20 inch barrel so I might be able to get you started in the right direction. The main thing is that you do a lot of reading here and in other places to learn.

 

[Das Capitolin]

Re: Greenhill Formula and .223 Remington

I plan on attempting maximum range targets, 900-1000 yards. I want to load with the best bullet to match my twist, but also to carry out that far (or better).

 

[Seawalker]

Re: Greenhill Formula and .223 Remington

Well somebody will be along shortly to give you the correct advice, but I don't think you can get there with a 1x9, nor do I think you can get there with the 69, but we'll see what the experts say.

 

[Das Capitolin]

Re: Greenhill Formula and .223 Remington

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Seawalker</div><div class="ubbcode-body">Well somebody will be along shortly to give you the correct advice, but I don't think you can get there with a 1x9, nor do I think you can get there with the 69, but we'll see what the experts say. </div></div>
I'll be waiting... since I've already reached a measured 800 yards with factory M193.

 

[JuniperEyes]

Re: Greenhill Formula and .223 Remington

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Das Capitolin</div><div class="ubbcode-body">I plan on attempting maximum range targets, 900-1000 yards. I want to load with the best bullet to match my twist, but also to carry out that far (or better). </div></div>

Greenhill or not, if you are trying to get to a grand at mag length the 77SMK and a stout dose of TAC is a good start for a 20in 1-9 AR.

Single-feeding is another story...

 

[former naval person]

Re: Greenhill Formula and .223 Remington

Greenhill breaks down with modern bullets. Works okay as good approximation with round nose lead bullets. Just query the guys here and on 6mmBR as to their experience with the .223 and 1000yds. No substitute for real experience. Since you are obviously going to build a rifle, why are you handicapping yourself with the standard .223? JMHO

 

[Das Capitolin]

Re: Greenhill Formula and .223 Remington

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: former naval person</div><div class="ubbcode-body">Since you are obviously going to build a rifle, why are you handicapping yourself with the standard .223? JMHO </div></div>Challenge? I could buy any gun out there and shoot it a mile, but it's more fun to seek out the maximum distance and work from there.

I'm looking for measurements and advice, please.

 

[Mordamer]

Re: Greenhill Formula and .223 Remington

Wow. If you are trying to go for 1000 yards then the best bullet for the job is going to be the 75 grain A-max. Many people have gotten it to work in 1:9 twist guns. If you can get it to shoot well it will carry to 1000 yards easily. I would start with that. If you can't get that to stabilize then I would suggest the hornady 75 grain HPBT. The Amax can't be loaded to mag length, but the HPBT can. You might not have the best results with these and the next best choice for a lighter bullet with a high enough BC to get to a thousand is the 70 grain berger VLD. The berger bullet is excellent and shot well for me even with a large jump to the lands.

 

[Seawalker]

Re: Greenhill Formula and .223 Remington

According to what I have, if you can push a 69g bullet at a muzzle velocity of 3,050fps, (which is what I can get with H4895 in a 22" barrel), you will go subsonic around 900 yds.

Wishing you the best in your endeavor, but your really need more twist and a heavier bullet IMHO. Like I said the long range guys will be along to help you out.

 

[Mordamer]

Re: Greenhill Formula and .223 Remington

Many bullets can retain stability through the transonic range and remain accurate after going subsonic. I recently read an article about a guy who shoots one mile with a .223 because of a dare he took. He is able to shoot sub-moa at one mile in the right conditions. Any .223 bullet is subsonic at those distances. The main bullet he used was the 80 grain Amax. However, you for sure wont be able to stabilize the 80 grainers. If you want to load to mag length then I think your best chance is with the 75 grain BTHP. This bullet will get to 1000 for sure.

 

[Das Capitolin]

Re: Greenhill Formula and .223 Remington

If 900 is as good as I get with repeated accuracy, than that's it I suppose. What kind of software would help me with this?

 

[Mordamer]

Re: Greenhill Formula and .223 Remington

You keep asking for software. Just use jbmballistics.com

You can use their trajectory calculator to see an estimate of where your bullet is going to hit and also when it is going to go subsonic. This calculator is very accurate I have found. Use it to compare wind drift with various bullets and drop with various bullets. If you need to know what kind of velocity you can push a certain bullet to then just look on hodgdon's website on their reloading data center and find a similar weighted bullet and what their max charge will push that bullet to. Just experiment some with these tools.

 

[Das Capitolin]

Re: Greenhill Formula and .223 Remington

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mordamer</div><div class="ubbcode-body">Just use jbmballistics.com</div></div> Thank you! This should be very helpful.

If there's anyone else with first-hand experience pushing .223 out to 1K yards with 1:9 twist, chime in!

 

[Seawalker]

Re: Greenhill Formula and .223 Remington

The best and only for sure way to tell is shoot the distance and see. What I meant was that it wouldn't be an ideal twist and bullet weight for 1,000. Do you have an idea as to what kind of muzzle velocity you can get with the 69's in your rifle?

My rifle will shoot the Hornady 75 hpbt okay with 1x9, but I can only get it to 2,800 fps which isn't any better at 1,000 than the 69 is starting at 3,050.

 

[Das Capitolin]

Re: Greenhill Formula and .223 Remington

So we can agree that the Greehill Formula is a bit dated, and there's a lot that changes with advances in bullet production. So far, these suggested websites seem promising for quality ballistics information: jbmballistics.com, kwk.us, and border-barrels.com.

Laurie gave me the best info here: http://forum.accurateshooter.com/index.php/topic,3766433.msg35959440.html#msg35959440

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">The 69gn Sierra MK, a bullet I would say is tailor-made for 1-9" twist 20" barrel .223s is 1.90, 1.66, and 1.43 for the three cases, in theory a bit 'over-stabilised', in practice not at all for any practical use of the cartridge.

The 73gn Berger is 0.970" long; the 69gn SMK 0.900", considerably longer than your 0.832" which would limit you to lighter non-optimal bullets BC- wise, although the definition of 'optimal' in this regard depends upon the distances you intend to shoot over obviously.</div></div>

I plan on shooting maximum range targets with this particular AR15, past 900-1000 yards. I've already reached 800 accurately, and I've seen 1000 yards, so I know it's possible. I'll use this same information to load with the best bullet to match a particular twist, and carry out as far as possible.

I'll be starting my tests with 69gr Sierra Matchking with 25gr Hodgkin Varget and develop from there.

 

[former naval person]

Re: Greenhill Formula and .223 Remington

You'll only get @6% improvement with a .223 Ackley Improved...but do consider it when you speck out your rifle. At those distances, 6% may make or break you. JMHO

 

[Seawalker]

Re: Greenhill Formula and .223 Remington

That load (25 Varget)gives me about 2,800fps. I'm shooting a 69 Nosler which is listed as having a little higher BC than the Sierra. 26g Varget gets me about 2,925 fps, but every rifle is different. My best load shooting Varget is 25.6g for about 2,850 fps.

Don't know if any of this will help you, but maybe give you some basic starting points. H4895 has been the powder that gives me the best velocity with 69's and still shoots sub.5 moa.

I hope you can make it work. Let us know how it turns out.

 

[Das Capitolin]

Re: Greenhill Formula and .223 Remington

Thank you for suggestions, Seawalker. Have you ever used Hornady 68gr BTHP Match Rifle bullets? They seem to offer the closest match for 1:9 twist.

 

[Jon Lester]

Re: Greenhill Formula and .223 Remington

7 twist allows me to do it with 77s@ mag length, but I have a lot better tools for that application.
The service rifle guys get it done with longer barrels but not sure on the twist.

 

[Seawalker]

Re: Greenhill Formula and .223 Remington

Sorry, haven't shot the 68's. Like most other bullets, some people sware by them and some people sware at them.