Mini-14 vs. AR-15


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lencac
September 18, 2007, 06:04 PM
OK guys here's a question for you all. Curious to see what y'all think. Some years ago while shooting on the plains of eastern Colorado with some friends we were shooting a 3/8 in. thick steel plate about a foot square. I was shooting my Match H-bar, 20 in. barrel, 1/7 twist and my friend was shooting his mini-14 also in .223. We were both shooting from the same can of 55gr. FMJ surplus ammo. At about 50 yrds. my AR was going through the plate like a paper punch through paper. His mini -14 was denting the plate but bouncing off. What gives? Twist rate? Gas system? Shorter barrel? What do you guys think?

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rcmodel
September 18, 2007, 06:13 PM
Velocity loss due to barrel length difference.

And some rifles are just faster due to the bore condition.
Maybe you got a fast Colt and he got a slow Ruger.

http://i81.photobucket.com/albums/j219/rcmodel/KTOG/1224.gif
rcmodel

RockyMtnTactical
September 18, 2007, 07:44 PM
It's hard to know without more detail.

TODD3465
September 18, 2007, 07:55 PM
I agree with rcmodel.

Standard military barrel length was 20" for years for the M-16 in 5.56NATO. The round was designed for that length.

Start cutting bbl length you start losing velocity. Lose velocity lose penetration that simple.

MudPuppy
September 18, 2007, 08:01 PM
It's hard to know without more detail.

What other details would contribute?

brian923
September 18, 2007, 10:11 PM
veocity would be the key factor. whats the difference between your AR, and his MINI?? i dont know about the gas system of the mini. maybe it uses more gas which steals some velocity?? i just guessing on the last thing though, just my .02$

Bazooka Joe71
September 18, 2007, 10:27 PM
It's hard to know without more detail.

What other details would contribute?


Because the Ruger isn't a Stag.:neener::neener::neener:

hags
September 19, 2007, 12:22 AM
The 1/7 twist rate was over stabilizing the bullet putting too much spin on it, it was literally drilling through the plate.





Just kidding!
More than likely the barrel length had alot to do with it. Velocity is king.
I was recently shooting at 3/8" plate steel as well. Both guns were ARs. I was using a 14.5" 1/9 twist barrel at 15 yards with 55 gr FMJ, they were bouncing right off. At 50 yards with a 24" 1/12 twist with 45gr balistic tips they were going right through, I had to put the rifle down and walk to the plate to be sure I saw what I thought I saw in the scope. Nice holes all the way through, I couldn't believe it.

Gator
September 19, 2007, 12:23 AM
Given the average accuracy of a Mini-14, what was denting the plate was probably rocks kicked up by the bullets hitting around the target.


:neener:

hags
September 19, 2007, 12:33 AM
Given the average accuracy of a Mini-14, what was denting the plate was probably rocks kicked up by the bullets hitting around the target.


Now that's funny!!!!!!!!!!

lencac
September 19, 2007, 02:49 AM
My advise ....... don't waste your money on a mini 14 .......

Eyesac
September 19, 2007, 01:50 PM
Hmm, that's interesting....

M92FS
September 19, 2007, 02:26 PM
AR-15 20" barrel : muzzle velocity 3280ft/s
Ruger Mini-14 18.5" barrel : muzzle velocity 3297ft/s

data from Palladium Books : The Compendium of Contemporary Weapons/The Vital Guide to Combat Guns & Infantry Weapons.

surprising Mini-14 got a higher muzzle velocity, I double check with The Vital Guide to Combat Guns & Infantry Weapons to make sure there's wasn't a typing mistake.

if your AR was going through the plate like a paper punch through paper at 50 yds, your friend Ruger Mini-14 should be the same. really can't tell what's wrong with your friend Mini-14. :confused:

rcmodel
September 19, 2007, 03:32 PM
That there just ain't right.
No way is a 18 1/2" barrel going to be faster then a 20" barrel. (Assuming both in new condition)
I don't care what Palladium Books says!

As for differences in gas systems, that won't fly either.
By the time any meaningful gas pressure is bled off through the gas port on either weapon, the bullet is long gone and well down range.

(Chamber pressure has to have dropped drastically before extraction can occur. And it can't drop until the bullet is out of the barrel.)

http://i81.photobucket.com/albums/j219/rcmodel/KTOG/1224.gif
rcmodel

kaizer
September 19, 2007, 04:18 PM
barrel length causing a difference in velocity, unless you guys were shooting different rounds.

romma
September 19, 2007, 04:49 PM
Was the ruger shooting tracer rounds?

Stretchman
September 19, 2007, 05:10 PM
Tighter barrel? Was his gun new?

Frog48
September 19, 2007, 05:18 PM
delete

Correia
September 19, 2007, 05:21 PM
AR-15 20" barrel : muzzle velocity 3280ft/s
Ruger Mini-14 18.5" barrel : muzzle velocity 3297ft/s

data from Palladium Books : The Compendium of Contemporary Weapons/The Vital Guide to Combat Guns & Infantry Weapons.

Uh, no. It doesn't work that way. Sorry Palladium books.

Frog48
September 19, 2007, 06:57 PM
Last edited by Correia : Today at 03:21 PM. Reason: Sorry Grant, funny, but Art's Grandma rules apply

Player hater! Haha, just kidding, its cool. :D

Acera
September 19, 2007, 09:06 PM
The mini-14's bullets might not have been as stabilized as the ARs, hitting the target with a slight kant, not dead straight like the ARs

benEzra
September 19, 2007, 09:17 PM
I'd put my money on velocity difference due to barrel length. Also, the average mini-14 has a HUGE gas port (AFAIK, it's a sewer pipe compared to the AR's gas port), which is why it kicks the brass out like a laterally mounted railgun. I always joked that my Ranch Rifle fired in two directions at once, and that I could defend straight ahead and my right flank at the same time. Hence, you may have quite a bit more pressure loss forward of the gas port in a mini-14, which could negatively impact velocity on top of the barrel length difference. Gas bleeding starts as soon as the bullet passes the 8" or 10" point on a mini (peak gas bleed occurs right after the bullet clears the port), and plenty of gas is vented before the bolt is unlocked; a mini's gas piston is HEAVY.

Re: yaw,

A tiny bit of yaw would probably be sufficient to rotate the bullet and slap the plate instead of penetrating when it hit something hard, and a mini will produce a bit more yaw than an AR due to the pronounced barrel bending moment caused by blasting that gigantic gas piston rearward off a cantilevered gas block. I don't know if it's enough to be significant, though; I'd say velocity difference is probably the primary answer.

lencac
September 19, 2007, 11:40 PM
Well, It is quite odd, but it did happen as described. Both firearms using the same can of ammo. I have chronographed both 55 gr. and 62 FMJ surplus rounds our of my AR. 55gr. right at 3100 fps and the 62 gr. 3000 fps. That was in Denver at 5200 ft altitude. I think this phenominon is due to a combination of things. Barrel length, gas system, and twist rate affecting stabalization of the round. Now here's a thought. Would not a faster twist rate cause more resistance to the bullet passing down the bore hence increasing pressure. So question, 2 AR's, one 1/7 twist, the other 1/9 twist. Same ammo, same barrel length. Does the 1/7 twist have a slightly slower muzzle velocity?

jaholder1971
September 19, 2007, 11:46 PM
I'd have to guess that the Mini's lose a lot of velocity courtesy of the gas system. I've seen newbies shooting Highpower rifle competition for the first time using Mini's resquadded because their brass was being thrown the entire length of the firing line. Having some newbie smacking people in the face with hot .223 brass doesn't win friends nor influence people.

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