Ruger Mini-14 Twist Rate vs. Accuracy


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Badger Arms
February 24, 2004, 02:17 PM
Looking at the book, Ruger and his Guns, I found that the twist rate of the Mini-14 started out at 1-in-10" in 1975. It then changed to 1-in-7" in 1989 and then finally to the current 1-in-9" starting in mid-1994. I'm wondering if this might result in the reports of poor accuracy we get often on this board. If you're shooting Military Ball ammo of the 55gr fodder out of the 1-in-7" barrel, you're not likely to get good results even in an AR.

The serial numbers are approximately:
1989: 185-56000 or for the Ranch Rifle: 187-84000
1994: 186-35000 or for the Ranch Rifle: 188-75000

These are rough numbers and I don't know if any better numbers exist. Any guns made before these is likely to be 1-in-10" and after these is likely to be 1-in-9" Twist. Inbetween you'll have 1-in-7" twist. Understand that for accuracy, none of these twist rates does an admiral job on the most common type of ammo available, the 55gr FMJBT.

So what does all this mean? If you have accuracy problems with your Mini-14, don't ditch it. Find out what your twist rate. If you're close, perhaps you should do the cleaning-rod/jag trick. Wrap a piece of tape around a cleaning rod and mark a line along the bore axis in . put a tight-fitting patch on a jag and run it down the bore. Count one turn and measure how for it's gone. This can get you pretty close, close enough to tell if the serial numbers above get you too close.

Now, if you have a 1-in-7 twist barrel, only buy 62gr or heavier bullets for it. In fact, I'd suggest 69 or 70gr bullets as that's about what your twist rate is optimized for. All other things being equal, you should see an increase in accuracy. If you have the slower twist rates, I'd still stick with a 62gr bullet and don't go down below 55 if you want it to be accurate. Just a suggestion, it might save you from ditching a good gun because you fed it wrong.

http://www.ruger-firearms.com/Firearms/images/Products/32L.gif

BTW, my current Mini's are 1976 and 1996 years of manufacture. My inventory Mini's are both 1-in-9" twist guns. I'll have to switch to the 62gr bullets and see if I can improve. Has to wait till summer, though.

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SodaPop
February 24, 2004, 02:47 PM
I'm wondering if this might result in the reports of poor accuracy we get often on this board.

It is.

I often say, "have you tried 62gr or heavier bullets?" And rarely do people say, YES. That Greek SS109 stuff isn't all that accurate, either, and most people don't find USGI M855 at gun shows. I've never seen the 8MOA with the 62gr and 69gr bullets, and I've gotten the barrel pretty darn hot.

I know the 1-7twist Minis are out there but I have yet to see one.

Badger Arms
February 24, 2004, 03:29 PM
It would seem that there are around 170,000 of them around assuming the serial numbers were sequential.

wanderinwalker
February 24, 2004, 03:31 PM
If you're shooting Military Ball ammo of the 55gr fodder out of the 1-in-7" barrel, you're not likely to get good results even in an AR.

This is not true of EVERY AR. Granted, mine is a 1-8" NOT 1-7", but SOME 55gr rounds will work well enough. Although the 1-7" twist may be overly fast for 55s and lighter, it will work well enough with the smaller slugs. Many shooters of HBARs and match-ARs report best results with lightweight 52gr bullets.

Okay, what I'm getting at is try a match Hollowpoint if you're in search of accuracy. Nolser Ballistic Tips reportedly work well also.

Badger Arms
February 24, 2004, 03:37 PM
Certainly there are more variables and the lightweight barrel of the Mini-14 certainly won't compete with a fee-floated 1" diameter stainless match barrel on an AR-15. As a general rule, 1-in-12" twist through 1-in-10" twist is the optimal accuracy zone for the 55gr Military Ball bullet. Some lighter bullets handle the twist rates differently. There is also the issue of velocity, ogive, etc. I don't want to get into that. The 1-in-7" twist rate is made to stabilize a MUCH longer and heavier bullet than the 55gr bullets most people shoot through them though.

P95Carry
February 24, 2004, 04:03 PM
Mine is a 185-93xxx .... 1:7 .... which i checked. It hates the cheapo Russian stuff ... all over the place and even tumblers too!!! In fact I keep meaning to mic up some sample bullets from the Russian ammo .. it's almost as if they are .223 instead of .224.

However .. put something thru like American eagle std 55 grainers and all improves immensely ... not good but acceptable. I really must start loading up some heavier bullets .. probably have not really tapped the gun's potential yet .... even tho I'd never expect quite a tack driver anyways.

Frohickey
February 24, 2004, 04:04 PM
I thought it was the shank of the bullet that is important with barrel twist, since that is what touches the barrel. I think the thin barrel of the Mini-14 is the main problem. Why couldn't Ruger just beef this up?

JNewell
February 24, 2004, 08:26 PM
I have both 1/7 and 1/9 ARs and shoot a variety of loads, mostly 55 and 62 gr. I really don't notice much difference. The difference between brands of the same weight bullet varies more than the difference between bullet weights. My current Mini is a 1/9 and frankly it is lucky to shoot 12 inch groups (and I use that term loosely, pardon the pun ;)) at 100 yards from the bench.

Badger Arms
February 24, 2004, 08:49 PM
12" Groups? I find that hard to believe. Not that I doubt you, but that's level of inaccuracy almost screams that there is something mechanical wrong like a loose sight, overtightened gas block, or barrel defect. I've never had a gun of any sort that I couldn't put in 5-7" at 100 yards.

4v50 Gary
February 24, 2004, 08:57 PM
My brother's Mini was 1-7" and he couldn't group with it and got rid of it. When I asked him what year, I told him he should have been shooting the heavier 62 grain bullet. :o I was taught that stuff in Armourers' School. Three weeks in NH was quite a nice training experience. :cool:

natedog
February 24, 2004, 09:24 PM
Hmm...this is odd...my Mini usually shoots 3" with the 45gr. Winchester White box JHP...Isn't it bullet LENGTH that requires a faster twist? Perhaps the 45gr JHPs are longer than most. Granted, a heavier bullet would be longer...I'll try some 69 and heavier stuff.

Edward429451
February 24, 2004, 09:30 PM
My FF Mini is 1-7" and I can do 4 to 5" groups at 100 with it with 55's. I haven't tried any 62's or 69's in it yet cause I got a 1-9" Bushy and have been playing with it of late. The AR does noticably better with 69's than 55's but I have yet to try the 62's in it either. I plan to soon time permitting but jeezow I'm swamped at work. Good thing but leaves little time for playing.

I've long suspected the twist rates were the problem with most Mini's accuracy. But the 55's are everywhere and cheap making them hard to stay away from.

mini14jac
February 26, 2004, 11:27 AM
I find that a lot of people who say the Mini won't shoot were putting Wolf through the gun.:barf:

Wolf is fine for blasting and fun, if your gun doesn't choke on it, but in the .223, it's not the most accurate round.

I recently had a 1985 Mini that would shoot 8" at 100 yards, with Winchester or Federal (55gr) Mil. Spec. ammo.
(Mind you this was with open sights, from a bench, with my not-so-perfect eyes.)
I bedded the stock, installed a smaller gas port, and made sure to torque the gas block evenly.
After that, shooting the 55gr. stuff, my groups shrunk to <2".
I never did put a scope on it.

I traded that gun, and now have a new one. I like the characteristics of the 55gr. round better than the 62gr, and I felt the 1in 9 twist would shoot better.

First time out, I got <1" at 25 yards, around 5" at 100 yards.
(Yes, with open sights.)

I plan on having the barrel cut, then either bedding it myself, or getting it "pin bedded".
Will also do the gas port, and torque the gas block screws.

I'm anxious to see what I end up with.

Badger Arms
February 26, 2004, 12:25 PM
Since this is a Mini-14 accuracy thread, could you post instructions for your modifications. Don't know what pin bedding is or where to find the smaller ports.

Jim Watson
February 26, 2004, 04:08 PM
My limited experience agrees with JNewell's. The quality of the bullet and barrel plus their tolerance idiosyncrasies make more difference than the bullet weight/length and twist rate matchup. Within the limits of adequate stabilization, I'm not talking about 80 grainers in a 9" twist. For example, my 788 mit 12" twist is more accurate with handloaded 60 grain Bergers than with 52s. The 9" twist ARS barrel on my Mini RR does better with the 52s.

Maybe I am just unlucky, but I haven't seen the military ball or commercial ersatz ball ammo that is accurate enough to gauge barrel quality. A Highpower shooting friend said he routinely shot USA 55 grain econo-ball at 200 and even 300 yards, that he had a good supply of a lot number accurate enough that he could save the match ammo for 600 yards. But it did not shoot worth a hoot when we were checking a new scope a few weeks ago. 7-year old ammo losing it? I dunno.

mini14jac
February 27, 2004, 08:46 AM
Badger Arms:

Glad to share what I've learned.
Most of my knowledge came from the Ruger Accurizing forum:
http://www.perfectunion.com/forums/index.php?showforum=55

I did find a less expensive source for the gas ports. Let me do some digging, and I'll post that info.
There is a guy by the name of Mike Knifong(sp?) on that board that does trigger work, glass bedding, and sells gas ports for reasonable prices.

I did the glass bedding on my last gun with a $20 kit from Brownell's, and there is still enough material left to do another gun or two.
Pin bedding is done by Accuracy Systems (www.accuracysystemsinc.com)
They epoxy two threaded sleeves in the rear of the stock, drill the receiver, and sink two hex screws in to hold the gun in place. They also drill one other hole forward and sink a steel pin in the stock. I haven't had this done yet, but it looks like it would be more permanent than glass bedding. Cost is $90 (plus shipping, I think).

I called a local gunsmith, to ask about getting my barrel shortened, and recrowned. (There is a school of thought that the barrel is too thin, causing it to "whip", so shortening or adding a flash hider stabilizes it.)
My 'smith said "You can't get a Mini to shoot better than 4" at 100 yards", and he didn't want to cut the barrel. Well, I had bedded mine at that point, and installed a gas port, and was getting 2" groups with open sights, so I knew he was in error.

The idea is, the receiver moves around under recoil, causing large groups. Bedding cures this.
The barrel heats up and bends or deforms, causing vertical stringing as it gets hotter. Shortening, or adding a muzzle brake cures this.

The Mini can be made into a sweet little shooter. It's a shame the factory doesn't do this stuff up front.

Edited to add:
With both of my guns, I've only shot 55gr ammo. Both were far more accurate shooting Mil. Spec. ammo, than when shooting Wolf or Norinco.
The good thing about a Mini, you can shoot Wolf, when you just want to have a blast!

W.E.G.
September 13, 2007, 08:31 PM
bump

silverlance
September 14, 2007, 02:42 AM
i can easily hit bowling pins at 100 yards, every shot, no misses with my 580 series mini14.

the ammo is wolf 55gr HP, copper jack lead core.
magazine is ruger factory 1980s.
rifle was bought used in a hogue stock.

that's plenty accurate for me.

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