The Firing Line Forums

Go Back   The Firing Line Forums > The Skunkworks > Handloading, Reloading, and Bullet Casting

Reply
 
Thread Tools Search this Thread
Old January 20, 2014, 12:11 AM   #1
skizzums
Senior Member
 
Join Date: July 1, 2013
Location: Douglasville, Ga
Posts: 4,615
best weight for twist

sorry, ii know i just posted a thread, but what is the best bullet weight for 223 1-300yards from a 1:8 twist? i am clueless about this kind of stuff
__________________
My head is bloody, but unbowed
skizzums is offline  
Old January 20, 2014, 06:22 AM   #2
overthere
Senior Member
 
Join Date: July 20, 2012
Posts: 290
69 gr bullets should serve you well at 300. For 100, 55 gr should still work well in a 1-8.
overthere is offline  
Old January 20, 2014, 10:34 AM   #3
Jay24bal
Senior Member
 
Join Date: December 13, 2011
Location: Cleveland, OH
Posts: 735
What is your barrel length? Assuming a standard 22" or longer barrel, you should be able to use pretty much any bullet you want to for the caliber.

I personally would start with 69s and even try some of the 75s and 80s.
__________________
I like guns.

Once Fired Brass, Top quality, Fast shipping, Best prices.
http://300AacBrass.com/ -10% Coupon use code " Jay24bal "
Jay24bal is offline  
Old January 20, 2014, 11:40 AM   #4
skizzums
Senior Member
 
Join Date: July 1, 2013
Location: Douglasville, Ga
Posts: 4,615
16inch, sorry its actually a 1:9 twist

so does that mean its better for the 55gr commercial, and the heaviers are for the slower twists?
__________________
My head is bloody, but unbowed
skizzums is offline  
Old January 20, 2014, 01:19 PM   #5
Jay24bal
Senior Member
 
Join Date: December 13, 2011
Location: Cleveland, OH
Posts: 735
Quote:
16inch, sorry its actually a 1:9 twist

so does that mean its better for the 55gr commercial, and the heaviers are for the slower twists?
I think you have the idea correct in your head, but it is coming out wrong.

Heavier bullets generally perform better in faster twist rate barrels. And the lower the second number in the ratio (the "9" in 1:9), the faster the twist. The twist rate is measured as how many times the bullet will perform a complete revolution in a given number of inches. Therefore 1:7 means it takes 7 inches of barrel for the bullet to spin 1 complete time, 1:10 means it takes 10 inches of barrel for the bullet to spin 1 complete time.

The length of the barrel comes into play as the longer the barrel, the more inches there are to work with and the more times the bullet will spin as explained above.

All of that comes together to generally mean that heavier bullets need more twist (whether it be the twist rate, length of barrel, or both) to stabilize them and provide the best accuracy results.

**As a caveat to everything I said above, there are other things that impact it such as bullet construction, bullet shape, and others, but for the most part, the points above are the basics.**

As to the main gist of the post, 55 grain bullets will be fine for your barrel (as would lighter ones) and I am assuming this is for an AR-15 based on the 16" barrel. Going heavier, you may be able to try heavier bullets, but only your barrel will tell you if it can handle them. Some will handle the 62 grain bullets, some will not, and you will most likely not be able to go over this weight, but the only way to know for sure is to test it with different loads.
__________________
I like guns.

Once Fired Brass, Top quality, Fast shipping, Best prices.
http://300AacBrass.com/ -10% Coupon use code " Jay24bal "

Last edited by Jay24bal; January 20, 2014 at 01:27 PM.
Jay24bal is offline  
Old January 20, 2014, 01:45 PM   #6
stnosc
Member
 
Join Date: September 13, 2012
Posts: 41
For 300 yards, 69gr SMK works great in a 1/9 twist. Berger also has a 73gr for 1/9 twist barrel. I've used them in my Savage 12BVSS 1/9 and they are very accurate also. I wouldn't recommend anything heavier for your 16" barrel.

For 100 to 200 yard accuracy, I've been getting sub-MOA with 53gr SMKs.

If you want a bullet for just general plinking and don't care a lot about accuracy, 55 grain FMJ will work fine (and they're generally cheaper).
stnosc is offline  
Old January 20, 2014, 01:51 PM   #7
Jay24bal
Senior Member
 
Join Date: December 13, 2011
Location: Cleveland, OH
Posts: 735
Quote:
For 300 yards, 69gr SMK works great in a 1/9 twist.
I agree 100%, depending on the length of the barrel. I also use Sierra's 69 gr MK HPBT in my 223 loads with a 1:9 twist, but it has a 22" barrel. With the OP having a 16" barrel, only trying it will tell.

I have two 16" barrels in 223/5.56, one with a 1:7 twist and one with a 1:9 twist. The 1:7 will handle 69 gr bullets well, but the accuracy falls off after about 150 yards with the 16" 1:9 barrel.

Quote:
If you want a bullet for just general plinking and don't care a lot about accuracy, 55 grain FMJ will work fine (and they're generally cheaper).
And I agree here as well. If this is the goal, we are splitting hairs that really do not need split.
__________________
I like guns.

Once Fired Brass, Top quality, Fast shipping, Best prices.
http://300AacBrass.com/ -10% Coupon use code " Jay24bal "
Jay24bal is offline  
Old January 22, 2014, 07:49 PM   #8
Catfish
Senior Member
 
Join Date: November 30, 2010
Location: Ohio
Posts: 171
If you are just shooting target the SMK 69 gr. should be about as good as you can do. That said, some barrels just don`t do thing like they should and another bullet may be better. For a hunting bullet, coyote and down size game, I like bullets in the 55 gr. range that expand well.
Catfish is offline  
Old January 22, 2014, 08:52 PM   #9
FtrPilot
Member
 
Join Date: September 4, 2010
Location: Woodstock, GA
Posts: 88
Best bullet for twist

Quote:
what is the best bullet weight for 223 1-300yards
For the 1 yard shot, I recommend a 230 grain .45 ACP or 240 grain .44 mag.

For 100 to 200, I personally like the hornady 55gr JSP.

For 200 to 600, I am loading 69gr Sierra Match King HPBT, with excellent results.


FtrPilot
FtrPilot is offline  
Old January 23, 2014, 03:53 PM   #10
semi_problomatic
Senior Member
 
Join Date: July 27, 2009
Location: Ft. Polk
Posts: 883
In the end, bullet weight does not matter. It is bullet length that matters (and actually only the amount touching the rifling...). Your best bet would be to start some where, say 62 grain bullet with whichever powder you choose out of whatever brass with whichever primers. Find it's accurate(est) load; then change one component at a time to see if x is better than y. For every X twist barrel can only handle Y or lighter/heavier bullets there are 3 guys saying my x twist barrels handle such-n-such just fine.

A few problems that you run into are barrel twist: what is written on the barrel may not be exactly true. I.E: my barrel says it's a 1:7. It's not. It's really a 1:7.7. You'd think they'd call it a 1:8 since it is closer to a 1:8 than a 1:7, but they don't. This holds true for many AR barrels. A 1:9 could be a 1:8.5 or a 1:9.7. Same with a 1:8. Bullet construction makes weight:length misleading, a ballistic tip may be longer in the same weight which could be true for an OTM, or a solid copper...etc. In the end, the only way to know is to try it and see.
__________________
Freedom's just a word. If I'm gonna die for a word, my word is jello...
semi_problomatic is offline  
Old January 24, 2014, 08:34 PM   #11
Unclenick
Staff
 
Join Date: March 4, 2005
Location: Ohio
Posts: 21,022
I have to say that kind of pitch variation is pretty large. There are some barrels cut to metric rather than English specs. A 195 mm pitch, for example, would be 7.68" twist. But no barrel I've ever ordered made missed by anything like 10%.

Length, weight, and velocity for a given pitch all affect stability. Length most, weight second, and velocity least.

I recommend looking at the stability calculator at the JBM Ballistics site. You can change bullet length, weight, or velocity, or rifling pitch and see the effect on the gyroscopic stability factor. Anything with a gyroscopic stability factor of less than 1.000 is theoretically unstable. Anything under 1.3 doesn't usually shoot very tight groups, even if not outright unstable. 1.4 to 1.7 are generally considered ideal for target shooting levels of precision, and 1.3 to 3.0 are Sierra's recommendation for "hunting accuracy". The calculator is an estimator based on a modified version of the old Greenhill formula that adds taking atmospheric conditions and velocity into account. But it's not a six degrees of freedom calculator (you have to know more about the bullet than is normally published to use a really sophisticated stability calculator; things like location of center of gravity and center of pressure and moments of inertia).
__________________
Gunsite Orange Hat Family Member
CMP Certified GSM Master Instructor
NRA Certified Rifle Instructor
NRA Benefactor Member and Golden Eagle
Unclenick is offline  
Old January 25, 2014, 01:23 PM   #12
RC20
Senior Member
 
Join Date: April 10, 2008
Location: Alaska
Posts: 7,014
Trying to get a quick reality check on Jay24bal that the longer the barrel the more spin.

My understanding is that barrel length affect velocity but not spin (nor accuracy) and once its spun up then more barre length makes no difference in staiblity. Longer barrel has to have twist to keep it there but does not add.

I assume that you can get too short, to make it dramatic, say a 5 inch barrel with a 1-10 twist

but 14 inch M4 gets them spun up though short of the intended round velocity.

Current M4 twist is 1-7 so thats two turns (less with the chamber adding to the barrel)
RC20 is offline  
Old January 25, 2014, 03:52 PM   #13
tangolima
Senior Member
 
Join Date: September 28, 2013
Posts: 3,769
I recently read about the Greenhill equation for calculating twist. Just wondering anybody still use that nowadays.

-TL
tangolima is offline  
Old January 27, 2014, 02:14 PM   #14
Unclenick
Staff
 
Join Date: March 4, 2005
Location: Ohio
Posts: 21,022
RC20,

I think he just means that if the barrel is longer the velocity is higher, so the RPM of the bullet is higher. It's still taking the same number of inches of travel to make one turn in the rifling, but at higher velocity it is covering that same number of inches more quickly, so each rotation also happens more quickly. Hence, higher RPM.

The general formula for RPM of a bullet, when the rifling pitch (P) is in inches and the muzzle velocity (MV) is in feet/second, is:

RPM = MV × 720 / P

So, suppose you have a barrel twist with a pitch of P=10 turns per inch, in a 24 inch barrel that fires the bullets 2,500 feet per second, the RPM is:

2,500 ft/s × 720 / 10 in = 180,000 RPM

If you then shorten the barrel to 18 inches, and that results in the MV dropping to 2,361 ft/s, you get:

2,361 ft/s × 720 / 10 in = 170,000 RPM
__________________
Gunsite Orange Hat Family Member
CMP Certified GSM Master Instructor
NRA Certified Rifle Instructor
NRA Benefactor Member and Golden Eagle
Unclenick is offline  
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 03:55 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
This site and contents, including all posts, Copyright © 1998-2021 S.W.A.T. Magazine
Copyright Complaints: Please direct DMCA Takedown Notices to the registered agent: thefiringline.com
Page generated in 0.05621 seconds with 8 queries