Ruger Mini-14 and Mini-30 Ruger Mini-14 and Mini-30 family of rifles

Reply
 
LinkBack Thread Tools Display Modes
Old 06-30-2012, 15:59   #1
Full Member
Points: 8,913, Level: 63 Points: 8,913, Level: 63 Points: 8,913, Level: 63
Activity: 0.8% Activity: 0.8% Activity: 0.8%
Last Achievements
 
Join Date: Mar 2009
Location: Illinois
Posts: 261
Twist Rate & Bullet Weight?

I am finally trying to figure out what my mini likes to eat.
The rifle it is a 196-5xxxx built in 2001 with a 1:9 twist rate. The barrel is 16" with a SEI muzzle brake and Guido Barrel Strut. Three shot groups from bags at 100yds. Ammunition was PRVI Partisan. (55, 62, 69, 75gr)
The results for each bullet weight were within 5" with one truly standing out over the rest.
The best grouping was under an inch .223 Match 75gr HP BT.

I don't want to look a gift horse in the mouth but I have read and been told that a 75gr bullet is too heavy for a 1:9 twist barrel.

Guido
Attached Thumbnails
Twist Rate & Bullet Weight?-100_1007.jpg  
__________________
NRA Life Memeber, NRA Certified Rifle Instructor, RWVA, CMP, ISRA
Guido is offline   Reply With Quote
Old 06-30-2012, 17:55   #2
communism hater
Points: 9,978, Level: 66 Points: 9,978, Level: 66 Points: 9,978, Level: 66
Activity: 4.5% Activity: 4.5% Activity: 4.5%
Last Achievements
 
Join Date: Feb 2010
Posts: 3,334
I have shot 75gr Hornady Match ammo before in my 1:9 twist 580 mini and they shot very well. I reload 69gr sierra and the 75gr were almost as accurate as my handloads. I tried them just to see if the mini-14 would stabilize them and it did.
__________________
United We Stand.. Divided We Fall.. Into the pits of socialism
qwman68 is offline   Reply With Quote
Old 06-30-2012, 22:13   #3
Full Member
Points: 9,751, Level: 66 Points: 9,751, Level: 66 Points: 9,751, Level: 66
Activity: 7.6% Activity: 7.6% Activity: 7.6%
Last Achievements
 
Join Date: Nov 2011
Location: California
Posts: 371
Originally Posted by Guido View Post
I have read and been told that a 75gr bullet is too heavy for a 1:9 twist barrel.
Heavier bullets may change the timing of your rifle's barrel vibration such that the barrel more often points in the same direction when the bullet exits. Smaller groups may not indicate improved bullet stability, but it certainly suggests bullet stability is adequate over the range you tested.

The picture may change if you shoot at extreme range, especially as the velocity drops off to approach the speed of sound. If 75 grain bullets work better for you at your intended range then that seems like a very reasonable thing to do. If you are interested or concerned, try this ammo at 200 and 300 yards to confirm its performance there.

It is not bullet weight but bullet length and position of the center of gravity relative to the center of (air) pressure that drives spin requirements. All bullets of a given weight are not equal.

Increased air density and low temperature can also take marginally stable bullets and cause them to yaw excessively or even tumble. What works at high altitude on a hot day may not work at sea level after a snow storm.
subscriber is offline   Reply With Quote
Old 07-01-2012, 11:51   #4
Full Member
Points: 8,913, Level: 63 Points: 8,913, Level: 63 Points: 8,913, Level: 63
Activity: 0.8% Activity: 0.8% Activity: 0.8%
Last Achievements
 
Join Date: Mar 2009
Location: Illinois
Posts: 261
subscriber
What you state sounds sensible to me.
Remembering that the PRVI 75gr didn't shoot well when I was experimenting with the Rutro Contraption I used it to sight in the tech sight. (use poor ammo to get on paper) I was suprised to find 1" groups 25yds then.

I should have pulled it out last weekend when we were qualifying out to 400yds but the mini and I were holding our own shooting XM193 against the AR/M1A shooters. Might have made a difference.

I don't know when I will get another chance to shoot past 100yds. I hope it's before next June.
__________________
NRA Life Memeber, NRA Certified Rifle Instructor, RWVA, CMP, ISRA
Guido is offline   Reply With Quote
Old 07-01-2012, 12:10   #5
CantRe Member
Points: 3,331, Level: 35 Points: 3,331, Level: 35 Points: 3,331, Level: 35
Activity: 27.5% Activity: 27.5% Activity: 27.5%
Last Achievements
 
ManyFeathers's Avatar
 
Join Date: Apr 2011
Location: Texas
Posts: 568
Stabilization has to do with the length of the bullet and not the weight

There is a relationship though with a heavier bullet being longer.

Here's a twist calculator

Barrel Twist Calculator
ManyFeathers is offline   Reply With Quote
Old 07-02-2012, 23:37   #6
Full Member
Points: 2,156, Level: 28 Points: 2,156, Level: 28 Points: 2,156, Level: 28
Activity: 13.0% Activity: 13.0% Activity: 13.0%
Last Achievements
 
Join Date: Feb 2012
Posts: 372
ManyFeathers is correct in his statement! There are other factors that will effect a barrels ability to stablize a bullet as well although they are subtle factors when compared to the bullets bearing surface length.

For example....a 75 gr bullet will be fairly stable in 1-7 twist M4. To shoot the same bullet from my 224 TTH dictated that I go to a 1-6 twist barrel to shoot the same bullet at about 3600 fps velocity.

There much more to the equation than just bullet weight.
LunaticFringeInc is offline   Reply With Quote
Old 07-03-2012, 07:46   #7
Full Member
Points: 8,913, Level: 63 Points: 8,913, Level: 63 Points: 8,913, Level: 63
Activity: 0.8% Activity: 0.8% Activity: 0.8%
Last Achievements
 
Join Date: Mar 2009
Location: Illinois
Posts: 261
feathers, fringe,
All very good. A rocket scientist I am not. I will have to put some lead down range to find out.
Guido
__________________
NRA Life Memeber, NRA Certified Rifle Instructor, RWVA, CMP, ISRA
Guido is offline   Reply With Quote
Old 07-03-2012, 08:40   #8
Full Member
Points: 860, Level: 15 Points: 860, Level: 15 Points: 860, Level: 15
Activity: 7.2% Activity: 7.2% Activity: 7.2%
Last Achievements
 
Join Date: Apr 2012
Posts: 172
The Sierra 69gr HPBT shoots well in my 197 Ranch Rifle. I had a hard time loading this bullet until i used a shorter COL that i found on Hodgdon's load data page. The 69gr Sierra bullet shot well for using 2.235 COL with 23.8gr of H335.
51
51colt is offline   Reply With Quote
Old 07-04-2012, 10:13   #9
Full Member
Points: 2,597, Level: 30 Points: 2,597, Level: 30 Points: 2,597, Level: 30
Activity: 0.9% Activity: 0.9% Activity: 0.9%
Last Achievements
 
Join Date: Sep 2009
Posts: 26
I have never had a problem stabilizing 75 grain SMK out of any 1:9 barrel. You should not have a problem with these out to 700 plus with a 9 twist. My rifle 196 series will hold close to MOA out to 500 with them. Jeff
persistant7500 is offline   Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

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
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -7. The time now is 08:53.
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Friendly URLs by vBSEO 3.6.1
All information is copyright by Perfectunion.com unless already under copyright.

This site is Gunny Approved