Velocity Loss Vs. Barrel Length in the Mini-30 - Shooting Sports Forum


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Old 03-19-2017, 14:55   #1
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Velocity Loss Vs. Barrel Length in the Mini-30

"Real World" testing, for those that gots to know!
Made it up to the range this morning before the rain hit and fired 5 rounds each through the chronograph of three different specimens of 7.62 x39 ammo, through three different barrel length Mini-30's.
I used my Chrony for the test, set 12 feet from the muzzle. I started at 15 feet, but was getting too many error readings so moved it in. 60 degrees, no wind, 5800 feet elevation, etc.
First up was the "Green" stock Mini. Dang, I need to name my Mini's, like Rosetta, Gwendolin, or the like, or at least number them, so I don't have to identify it by the stock it has.
It has a barrel cut to 16 1/4", with a Choate flash hider, and with the stock (big) .100" bushing, throws brass about 12-15 feet, like my other two do with a .060" bushing. So this shorter barrel needs more gas for sure.
First up was the:
PPU ( Privi Partisan) factory 123 grain FMJ
2321 fps. average ( low 2305---high 2338)

Reloads with 123 grain Hornady SST, A2015 powder in a PPU case
2465 fps average ( low 2449---high 2487)

Red Army Standard Russkie 123 grain HP ammo
2742 fps average (low 2727---high 2756)
Gadzooks !! This load is smoking hot, getting into low .308 Winnie range.
But not so consistent in velocity in the other two Mini's, as we shall see.

Next Mini is my wood stocked one, a 17 1/4" barrel and a Choate flash hider as well, and I use a .060" bushing in it.
PPU FMJ:
2366 fps average ( low 2345---high 2388)

My "load" with SST bullet:
2120 fps average ( low 2101---high 2140)
Surprised my Favorite hand load shot so low in this Mini, but in the other two Mini's, velocities were more as expected.

Red Army Standard steel case HP bullet:
2565 fps. average ( low 2429---high 2702)
A lot more variation, but still a high velocity factory load.

And the last Mini has the original length 18.5" barrel, that I threaded and put a Ruger flash hider on. It also likes a .060" bushing, likes Italian food, action movies, and is not shy on first dates. I usually, for lack of a better name, call it the "Grey" Mini, because of the Cerakote color it has.
PPU FMJ
2375 fps. average ( low 2364---high 2388)
Nice, low spread of velocity, typical of PPU ammo. My groups with it attest to good charges.

SST Hand loads:
2350 fps. average (low 2321---high 2380)

Red Army Standard 123 grain HP:
2584 fps. average (low 2413---high 2756)
Stout load in this Mini as well.

A few loopers, how fast the Red Army stuff was. I shot 15 rounds for the test, and blasted 25 more round of it downrange at steel targets, and had one fail to fire. I have bought several boxes of Red Army before, so out of 100 rounds, one failure, from Mini with the stock firing pins in them.
(I have longer fitted ones stashed away for emergencies).
I noticed the same of the Hornady factory loads with the SST bullet. They are loaded with a steel case to cut down on price so Berdan primed, but I had 98 out of 100 fire fine with stock firing pins. But because of the premium bullet ( and accurate too I can say) it sells for much more than the Red Army Standard. The Hornady is $40 for a 50 round box, but would be excellent for home defense, sane sized deer or hogs or zombie apocalypse.
The Red Army stuff is $5.99 for 20 rounds. So there is better stuff than Tula to blast and plink with ! Much better reliability than the Tula I've shot.
If I ever need to shoot ANY Russian ammo on a regular basis I'll slip in my longer aftermarket pins I fitted, for 100% ignition reliability.

In a different format to more easily compare differences in barrel length, here they are:
----16.25" barrel------------------17.25" barrel-------------18.5" barrel----
PPU Fact. FMJ 2321 fps. PPU Fact. FMJ 2366 fps. PPU Fact FMJ 2375 fps.

- --- 16.25" barrel-----------------17.25" barrel-------------18.5" barrel-----
SST handload 2465 fps. SST handload 2120 fps. SST handload 2350 fps.

----16.25" barrel------------------17.25" barrel--------------18.5" barrel----
Red Army HP 2742 fps. Red Army HP 2565 fps. Red Army HP 2584 fps.

Weird how my Hornady SST hand loads were fastest in the shortest barrel length, and slowest in the mid length barrel.
And how the Red Army Standard Bolshevik ammo was the fastest in the short 161/4 inch Mini as well.

The Mini's tested, plus my 59 year old Marlin Mountie .22 that I wanted to burn a lot of ammo through after the velocity testing of the Mini's:

I have to sneak in another picture of the Marlin Mountie and my 1973 Colt New Frontier .22 sixgun.
I've fired about 700 rounds through them the last couple weekends of spring like weather we've had, and I'm continually impressed with how accurate both are and so well made, definitely a high point of American craftsmanship.

Last edited by sandog; 03-20-2017 at 18:23. Reason: punctuation.
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Old 03-19-2017, 15:34   #2
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Really great info, sandog. Thanks for doing all that testing and sharing the data. I'm saving this for reference. Interesting variations on many levels that would be hard to predict using formulas. Nice Marlin Mountie, by the way.
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Old 03-19-2017, 15:41   #3
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Thanks for the data Sandog... And a great job on it!!

The PPU really does not care much about barrel length and the Russian and your loads really like a short barrel. To me it looks like around 17 inch is the sweet spot for a mini 30 barrel length. Really not much difference in velocity overall though. I would of thought there would be more. The science around the way powder burns is pretty interesting.
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Old 03-19-2017, 15:52   #4
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Doesn't get much better than that. Very useful information for Mini 30 owners. Especially the velocity figures on the PPU ammo. Thanks for the effort of testing and posting up the results. Great post.

Oh, btw that Marlin and Colt look right at home together. Nice iron.
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Old 03-19-2017, 19:33   #5
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Great job SD, very interesting results!
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Old 03-19-2017, 22:50   #6
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I always thought that the 7.62x39 in a Mini-30 should be able to send a 122 to 124 gr projectile out of the muzzle at 2600 fps with the right powder, and without exceeding pressure limits.

It was Ruger that significantly raised max average preasure limits from what the SAMMI standard was before developement of the Mini-30 began. (20-inch test barrel). IMO, the potential for the 7.62X39 cartridge has never been fully explored and utilized to this day.

20 years ago people were loading 130 and up to 140 gr bullets for 7.62X39. There was a lot of talk then that 140 gr @ 2350 FPS was ideal for the caliber. I have some 130 gr 7.62X39 and quite a bit of 125 gr 7.62X39 from back in the day. I never did get my hands on any 140 gr though I knew it was out there.

In the 1990 Ruger paper catalog I still have they suggest a 125 gr bullet @ 2329 FPS for the Mini-30 when comparing it with other calibers. That's very modest considering what the Mini-30 was designed for.

I always thought the 7.62X39 could do anything the 6.8 SPC could do.

It's funny to me when I read claims that the 6.8 SPC "easily outperfoms the 7.62.39" because the 7.62X39 can match it. Put a lighter 115 grain bullet in the 7.62X39 and it can easily match the 6.8 SPC and its lighter 115 gr bullet.

Well, I'm drifiting off topic if I'm not careful, but these tests bring those things to mind. The design of the more strait-walled casing of the 6.8 SPC is arguably better for a number of reasons. That being said, Finland decided to stay with the 7.62X39 until at least the year 2035 after considering other options a couple years ago.

I don't know what AK and AKS variants can do, but the Ruger Mini-30 in particular was designed to do more with the 7.62X39 than it's officially doing these days. I'm happier than ever to own a Mini-30 and glad I made the decision all those years ago to choose it over any other options and any other calibers available in 1989 when I bought this beauty.
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Old 03-20-2017, 06:30   #7
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thanks for interesting report. to add to this the 'sst' bullet was (may be - hopefully still is -) available from Graf's. I bought 500 of them some years back very reasonable price. sorry, don't have stock # around. very good results with this bullet and amazing damage to water filled milk jugs. literally explodes on impact I'm not sure it should be used on larger than medium sized wild game.
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Old 03-20-2017, 06:50   #8
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I was shocked at the Red Army performance in the shorter barrel.
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Old 03-20-2017, 07:36   #9
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faster powder likely. maybe ball.
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Old 03-20-2017, 17:36   #10
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I'm thinking faster burning powder with the Red Army as well. I remember back in the 90's when law enforcement agencies were looking to buy carbines in the same caliber as their pistols. I read lots of test results published in various paper mags back then.

Some early versions of the carbines they tested failed to launch 9mm and 10mm bullets at any faster velocity than a 4-inch barrel pistol could, and surprisingly some of the 9mm carbines with 18-inch barrel tested lower in velocity than a 4-inch to 5-inch barrel pistols.

The art of powder selection seems to be mostly science with a little bit of voodoo thrown in for good measure.

I haven't ventured into reloading yet, but I think that may be one of my next steps. I looked into it many years ago, but something always came up that took too much of my time.
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Old 03-20-2017, 19:44   #11
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Wow! Sandog you really did a superb job. Thanks so much!
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Old 03-21-2017, 04:17   #12
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It seems the PPU ammo was the only one that showed "normal" velocity progression as the barrel length increased.
It would also seem the powder in the Red Army Standard and my handloads was optimal for short barrels.
I can't explain though, why my SST handloads got 300 fps. less in the "mid" length barrel on the wood stock Mini, but the other two Mini's shot the SST load at normal velocities.
The wood stock gun shot the other two loads at velocities that were expected, but not the SST load ? Weird.
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Old 03-21-2017, 06:16   #13
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did you mike the o.d. of the sst slugs you handloaded? if you loaded .308 dia then a bit of blow-by would do that.
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Old 03-21-2017, 07:15   #14
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No blow by. They are .311 bullets.
And they shot normal in the other two Mini's.
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Old 03-21-2017, 08:59   #15
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Originally Posted by Beck View Post
I'm thinking faster burning powder with the Red Army as well. I remember back in the 90's when law enforcement agencies were looking to buy carbines in the same caliber as their pistols. I read lots of test results published in various paper mags back then.

Some early versions of the carbines they tested failed to launch 9mm and 10mm bullets at any faster velocity than a 4-inch barrel pistol could, and surprisingly some of the 9mm carbines with 18-inch barrel tested lower in velocity than a 4-inch to 5-inch barrel pistols.

The art of powder selection seems to be mostly science with a little bit of voodoo thrown in for good measure.

I haven't ventured into reloading yet, but I think that may be one of my next steps. I looked into it many years ago, but something always came up that took too much of my time.
No voodoo or surprise with the carbine test velocities at all. You see, 9mm, 40s&w, 45acp, 10mm are all modern calibers specifically designed to produce high velocities in barrels shorter than 6". They all have very compact cases with small powder capacities. In addition, their powders are specifically formulated to be used in short barrels.

None of them perform well in longer barrels compared to calibers like 357 Mag, 41 Mag, 44 Mag, or 45 Colt, all which have larger cases holding significantly larger, magnum powder charges. These actually benefit from longer barrels such as leverguns. For example, my 357 Mag full power loads using H110 magnum pistol powder produce higher velocities in my 24" Rossi rifle than they do in my 20" Rossi carbine.

Now, if you load up those same calibers with non-magnum powders formulated for use in short barrels, they also don't do well in longer barrels. For example, my 38 Spl standard power loads using Unique pistol powder produce lower velocities in my 24" Rossi rifle than they do in my 20" Rossi carbine.

That's the real benefit of handloading your own ammo. You can tailor your loads to fit the firearm, bullet style and weight, and specific purpose you want, not what the ammo manufacturer decides you want.
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Old 03-21-2017, 17:51   #16
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Originally Posted by COSteve View Post

None of them perform well in longer barrels compared to calibers like 357 Mag, 41 Mag, 44 Mag, or 45 Colt, all which have larger cases holding significantly larger, magnum powder charges. These actually benefit from longer barrels such as leverguns. For example, my 357 Mag full power loads using H110 magnum pistol powder produce higher velocities in my 24" Rossi rifle than they do in my 20" Rossi carbine.

Now, if you load up those same calibers with non-magnum powders formulated for use in short barrels, they also don't do well in longer barrels. For example, my 38 Spl standard power loads using Unique pistol powder produce lower velocities in my 24" Rossi rifle than they do in my 20" Rossi carbine.

That's the real benefit of handloading your own ammo. You can tailor your loads to fit the firearm, bullet style and weight, and specific purpose you want, not what the ammo manufacturer decides you want.
Yes, Exactly.

My older Rossi Model 92 with 20-inch barrel launches 357 Magnum loads several hundred FPS faster than will my 4-inch barrel wheel gun in the same caliber.

I don't know for sure, but I wonder if past good experiences pairing lever actions with revolvers in the same caliber lead to some expecting similar success when pairing 9mm and 10mm carbines of the day with semi-auto pistols in a matching caliber.

I'll have to dig up a couple old gun rags to refresh my memory of the details... what particular carbines and what rounds gave what results. It's old news now, as these days people have good success with 9mm carbines in AR and H&K formats among others with 16-inch barrels.

I only mentioned it in passing because it was one of my first reads regarding different brands of ammo and various barrel lengths. Some of the carbines did better than others of the same length. Those tests from the early 1990s were notable for the inconsistent results. It had the people running the tests scratching their heads. I'm sure so many things come into play such as bore size, twist rate, etc.

My 189 series Mini-30 has the .308 bore with the Lapua style chamber and forcing cone to handle .311 diameter bullets. I don't recall if any of sandog's Minis have that or not. It seems like most people have the Mini-30 with the .310 bore. sandog's tests inspire me to finally get around to buying a chrono to find out what my Mini-30 favors. That will surely get me to think about tweaking things, and before you know it I'll be into reloading.
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Last edited by Beck; 03-21-2017 at 18:40.
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Old 03-23-2017, 09:48   #17
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Great job, Sandog.

Here are Mini 30 stock barrel lengths as posted online.

Barrel length
22.00 in (559 mm) (Target Rifle)
18.50 in (470 mm) (Ranch Rifle, Mini-30)
16.12 in (409 mm) (Tactical, Mini-30, NRA Edition)
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Old 03-23-2017, 10:40   #18
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It all comes down to how big the case is and the powder type one uses. 'Magnum' pistol powders (usually originally developed for shotguns) don't peak as high so they rely on larger charge loads to produce more velocity in handguns. That requires a large case to hold the large charge and they therefore, work very well in longer barreled rifles as the greater volume of powder gets a longer time to produce the accelerating gas pressures. Compare that to small charge, high pressure loads in modern semi-auto calibers and note that they rely on very fast, high pressure charges to ramp up the velocity very quickly.

As an example of what this means in a real world practical application, I need only look to 2 of my more favorite calibers, my 10mm and 357mag. My hottest 165grn 10mm load produces a whopping 1,589fps in my custom 6" Glock G20L, much faster than my hottest 158grn 357mag producing 1,382fps out of a 7.5" SA pistol. However, take those same loads and my 158grn 357mag produces 1,977fps in my 24" Rossi (1,941fps in my 20" carbine) but my 165grn 10mm only produces 1,691fps in a friend's MechTech 10mm 16" carbine.
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Old 03-23-2017, 22:39   #19
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Sandog, Glad to see you've taken the time, expense and energy to do the testing on barrel lengths, and ammo, on the Ruger Mini 30. As a comment: I hope that you'll find the time to test the SST loads, in you're three Mini's again, as I'm very interested to see if you will get similar velocity results through the three different barrel lengths. In no way am I disparaging your results, but I think that further testing would be of great interest, as three hundred feet per second difference, in velocity, is a very significant variation when considering that the differing factor, in the barrels, is a one inch difference in length, especially when the velocity variation is in the opposite direction of what one would expect. The velocity differences in the Red Army ammo were also interesting, but the SST data is my main interest. Thanks, Gary
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