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Old August 23, 2020, 10:46 AM   #1
jski
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Ruger Mini-30 bore diameter

What’s the bore diameter of a Ruger Mini-30 manufactured today:
.311 or .308 ?

I read that in 1990 Ruger standardized all their barrels to .308, including those chambered for 7.62x39?

Last edited by jski; August 23, 2020 at 12:46 PM.
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Old August 23, 2020, 11:08 AM   #2
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Ruger says 308
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Old August 23, 2020, 11:19 AM   #3
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Quote:
Originally Posted by 51cskipper View Post
Ruger says 308
Absolutely NOT!! Ruger has always maintained, and maintains today that their Mini-30's bore is .311. There are claims on the internet that very, very early models of the Mini-30 had .308 barrels but Ruger denies that this is true.

So, who you going to believe? A faceless, nameless, poster with no responsibility or liability for misleading/inaccurate information? Or, are you going to believe the manufacturer of the item who has an actual financial and civil/criminal liability for providing misleading/inaccurate information?

Go to the source. Call Ruger CS and ask them yourself.
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Old August 23, 2020, 12:44 PM   #4
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From Brownell's

This rifle is chambered for the 7.62 x 39mm cartridge. This cartridge, traditionally, uses a projectile with a nominal diameter of .311 to .312 inch.

At the time the Mini-30 was introduced very few bullet makers where producing .311/.312 inch bullets for reloading in the light 125-130 grain weight required. Ruger initiated the use of barrels with a groove dimension of .308 inch and a long tapered throat. The throat allowed the use of ammunition with .311/.312 projectiles by gradually squeezing them to the .308 diameter. In addition, ammunition loaded with more commonly available .308 diameter bullets could also be used.

Commencing in 1992 Ruger initiated a change to using .311/.312 nominal groove diameter, 1-10 inch right hand twist barrels in all Mini-30's. It was likely well into 1993 before all rifles coming of the production line incorporated the .311/.312 barrels
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Old August 23, 2020, 02:02 PM   #5
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Brownell’s is pretty much “ground truth” with all things firearms.

Last edited by jski; August 23, 2020 at 02:07 PM.
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Old August 24, 2020, 05:34 AM   #6
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Quote:
Originally Posted by 51cskipper View Post
From Brownell's

This rifle is chambered for the 7.62 x 39mm cartridge. This cartridge, traditionally, uses a projectile with a nominal diameter of .311 to .312 inch.

At the time the Mini-30 was introduced very few bullet makers where producing .311/.312 inch bullets for reloading in the light 125-130 grain weight required. Ruger initiated the use of barrels with a groove dimension of .308 inch and a long tapered throat. The throat allowed the use of ammunition with .311/.312 projectiles by gradually squeezing them to the .308 diameter. In addition, ammunition loaded with more commonly available .308 diameter bullets could also be used.

Commencing in 1992 Ruger initiated a change to using .311/.312 nominal groove diameter, 1-10 inch right hand twist barrels in all Mini-30's. It was likely well into 1993 before all rifles coming of the production line incorporated the .311/.312 barrels
I never actually measured mine, it was one of the very first ones produced. The only thing I ever noticed, not knowing there was a difference in the bullet diameters, was whenever I shot 7.62x39 Russian ammo vs my .308 diameter handloads was the Russian ammo was a lot hotter with much more noticeable recoil and the action was way more vigorous and ejection really tossed the cases way out there. It was after noticing this that I learned about the different sized bullets and just attributed the difference in how they fired to the different sized ammo. I also quit using the Russian ammo after that just to be safe.
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Old August 24, 2020, 10:33 PM   #7
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Old August 25, 2020, 01:15 AM   #8
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archives

Somewhere in the archives, I have an article, clipped from the "American Rifleman" (I think) on the 7.62x39mm cartridge and reloading for same.

Wait one!!!!!!!!!!!!

Okay, I went and found it. April, 1990! Written by C.E. Harris, who states he "worked extensively at Sturm Ruger &Co during the development of the Mini30." In a later paragraph Harris goes on to say the SAAMI chamber used by Ruger ...."follows the form used by the Lapua Cartridge Factory (Finland). It has a gradual forcing cone to ease the bullets transition from the .311" ball seat into the Rugers's .308" groove diameter, vs. .310-.311" common in European rifles of this caliber."

Clearly, Harris was working with .308 bored Mini30 rifles prior to and likely up to 1990. That's thirty years ago, documented and in print. I doubt there's anybody left answering Rugers customer service phones that was even employed by them at that time. There may not be anybody left in the company from thirty years ago........but Harris put it in print. I have previously read Brownell's blurb and it aligns with Harris's comments from 1990.

Harris's conclusions, and my own observations, (with my early Mini30) is that .308 and .311 bullets in the EARLY Mini's, made little difference accuracy and pressure wise. The Mini is not known as a match rifle, period. However, my later, Ruger 77MKII, acquired in the mid 90s) also chambered in 7.62x39mm, shoots .311 bullets noticeably more accurately than .308, and I suspect my M77 is bored .311.
Note I have never slugged either.
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Old August 25, 2020, 06:28 AM   #9
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Makes me wonder why they ever changed the design. Seems like a pretty good way to deal with this issue. Granted accuracy wasn’t the best, but with a little polishing on the trigger, removing 1 3/4 coils from the disconnect spring, and going to good handloads mine shot 1.75 MOA out to 200 yds pretty consistent. That was good enough to take several deer over the years.
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Old August 26, 2020, 12:35 AM   #10
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Why?

The need for gradual cone on the early Mini's was due to Ruger apparently using .308 bored barrels at that time. I've read some internet chatter as to why they might do that, but I'll not go down that path here. But I'd suggest it was some type of cost/efficiency matter. Ruger started making their own barrels 1990-91, prior that, they used contract barrels. I'd think that the "one size fits all" approach spares the need for .310-.311 barrels and almost certainly had to be cheaper.

When Ruger got it's own barrel manufacture program established, they might well have decided to make the switch to .310-.311 around that time, as US made ammo was becoming common with .310" slugs, and Ruger now had control of the barrel making process. The dates seem to match, loosely anyhow. Purely speculation on my part.
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Old August 26, 2020, 05:25 AM   #11
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That’s kind of what I was thinking too. I really miss my Mini 30, one of those guns I wish I’d never sold, along with my Mini 14 with the factory folding stock. I’d love to get replacements but price wise these days I tend to choke a bit. I’d love to take a newer Mini 30 and give it the CoSteve treatment to look like a Mini M14, now that would be cool.
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Old August 26, 2020, 01:24 PM   #12
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more "proof"?

Digging to my in archives a bit more, I came up with an article I clipped from Guns & Ammo magazine written by Ross Seyfried. The piece is dated August 1987 and appeared in the "Proof House" portion on the magazine that reviewed new gear and guns. The article is simply titled "Ruger Mini-Thirty".

In the final paragraphs, Seyfried addresses the .310 diameter bullets of factory ammo, but states, "The Ruger rifle has a standard .308 inch barrel, but has a long throat to safely accommodate the standard military and commercial ammo with the .310 inch bullets."

I'd posted earlier that C.E Harris, worked at/with Ruger on the Mini30 and published a similar comment. Here is another printed statement indicating that, at one point in time, the Mini-30 had a .308 bore. Note this statement is made in 1987, 3 years BEFORE the 1990 Harris article. These are two separate, printed, published articles by established authors, not internet babble. Admittedly, Ross Seyfried was a gun scribe and not a Ruger associate, but he wrote well and was not prone to exaggeration or error. I alway liked Seyfried's articles, and this one on the Mini-30 convinced me I would have one some day. I hope they keep making it, but I am not so sure.

The Brownells commentary, and Rugers stance at this time, leads me to think that NOW the Mini-30 does indeed have a .310 bore , but there are very good indications that early on, some Mini's had a .308 bore...... whether Ruger will admit it, or there is anybody left that remembers.
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Old August 27, 2020, 03:07 PM   #13
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I have always assumed it was 308 but perhaps I’m wrong.
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