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

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Old 07-27-2009, 12:52   #1
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6.8 SPC II chamber

Has anyone tried to ream the standard Ruger 6.8 SPC I chamber to the "correct" SPC II or DMR chamber without removing the barrel from the action? I know that you really should have a 1:11 twist barrel, but at least the correct chamber would reduce the pressure in the barrel with the original Remington chamber design that Ruger copied. John
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Old 07-27-2009, 13:15   #2
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Haven't yet heard of anyone on this forum doing it, although I recall brief discussion of it. I think someone on the 68forum had the reamer, but not sure if the feasibility for the Mini-14 was ever determined.

As long as you're not shooting the hotter "combat" loads specifically for Spec-II chambers, I wouldn't think that there would be any issues with the Mini-14 in 6.8 SPC.


ETA- Here's a link to previous discussion:

question about ammo for 6.8mm SPC Mini-14
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Last edited by Drifter; 07-27-2009 at 13:21.
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Old 07-29-2009, 07:13   #3
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use the tell the ceo and email questions links at ruger.com and maybe we can get them to change the chamber and twist rate. I've done both and the reply was," we will forward your request to our marketing dept. for study."
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Old 08-03-2009, 16:31   #4
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went to gander mountain today, talked to the gunsmith. He is checking with the gunsmith headquarters in Kenosha to see if there is an spc II reamer. Cost would be a little steep at $150 so I'm checking another local gunsmith.
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Old 08-04-2009, 16:04   #5
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At the bottom are some interesting links to info about the 6.8 SPC and the different chambers, the original, specII & DMR.
If you cut anything other than the leade of the chamber I think you would have to head space the barrel to the bolt again. The DMR chamber looks to be slightly different in specs than the Ruger chamber (original) at a critical point and may not match up with the new reamer, so you would have to cut back the shoulder of the barrel & re-time the gas hole to the receiver, lot's of work.
I have been going around with the 6.8 over the mini 30 for awhile now trying to decide if it is worth the leap to go to the 6.8, even if you have to modify the chamber a bit to get the velocity the 6.8 is capable of. The 6.8 out of a mini even according to Rugers catalog are far below what the round was first claimed to be. Ruger says velocity of the three different Remington 115 grain loads for in the mini 6.8 average out to be 2450fps that is a resulting energy of 1533 ft lbs. That is far below the Remington claims in its ballistics figures of 2650 fps. Why the difference I don't know, but these are Rugers own figures from pg 60 & 61 of their 2008 catalog. Seeing that the AR crowd is getting their max velocity out of 18" barrels seems to let the barrel length out of the equation.
2350 fps is easily attainable out of a mini 30 with a 125grain bullet for the exact same energy 1533 ft lbs. So the only advantage of the 6.8 out of a stock mini that I see is trajectory and better retained energy at longer ranges.
But if you modified the chamber of the 6.8 mini to take the higher pressure that the round was designed for then it would be worth it. 2650 fps or 2750 fps would make the round much more viable than the 7.62x39, making it harder hitting at close ranges and flatter with better energy retention at longer ranges.
If I were going to do it I would probably put witness marks on the barrel/receiver connection, pull the barrel, have the leade increased to the specII chamber specs with a .270 caliber throater (about 50 thousandths more) (and have the barrel cyroed as long as it was out) reinstall the barrel to the witness marks and see what happens. That way I'm not messing with cutting the chamber and messing up the head space. The extra leade would allow it to handle the higher powered combat loads from SSA, according to Art Kalwas, the owner of Silver State Armory. I wouldn't mess with trying to cut a new chamber as much more work would be required to reinstall the barrel. The other thing the mini has working against it is the twist and number of grooves in the barrel, unless you went with the type of barrel that the AR people are using, with a slower twist and less lands & grooves to reduce friction to increase velocity without building up pressure you will never be able to SAFELY get the kind of velocities the AR people are getting from the 6.8 which is right at 2800 fps & 2000 ft lbs of energy with a 115 grain bullet.Still if you can get 1750 ft lbs of energy with a slick 115 grain bullet at 2650 fps I think it would be worth it.
Anyway these links have a lot to offer if you take the time to read them.

The 6.8 SPC (6.8 x 43 mm) Cartridge be sure to click on the link in the article for the chamber drawings, remember you are seeing the chamber not the cartridge.
Today's State of the Art in 6.8 X 43 mm SPC good read lays out the 6.8 story.
Here is a link to the Reload Bench which has drawings of the 6.8 SPC CARTRIDGE, as well as some others. scroll down to the metric section and click on 6.8SPC.
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Old 08-04-2009, 17:04   #6
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Next year, I'm going to use my tax return money to get the guys at Accuracy systems to bore and stroke my Mini-14 .223 into a 6.8 SPC II rifle with a bull barrel.

Jim
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Old 08-10-2009, 21:32   #7
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Originally Posted by jimbobborg View Post
Next year, I'm going to use my tax return money to get the guys at Accuracy systems to bore and stroke my Mini-14 .223 into a 6.8 SPC II rifle with a bull barrel.

Jim

Nice try, but they do not list the 6.8 as a conversion for the 223 Mini. I already asked.

It's my understanding (from reading), the 6.8 is built on the 223 receiver, and the 7.62x39 is a stronger one. Anyone know any different?
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Old 08-10-2009, 21:45   #8
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Originally Posted by handirifle View Post
Nice try, but they do not list the 6.8 as a conversion for the 223 Mini. I already asked.

It's my understanding (from reading), the 6.8 is built on the 223 receiver, and the 7.62x39 is a stronger one. Anyone know any different?
Hmm, that's weird. I saw it listed on their site. Oh well. I'm ditching the extra Mini-14 I have since I can't do that now. Don't need two .223s.

Weird thing, I believe that the 6.8 magazine well is bigger than the .223 magazine well. At least according to ATI. Why is it weird? I have an AR that I'm building in 6.8 and the 6.8 marked magazines fit in the standard .223 magazine wells. IDK what Ruger was thinking.

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Old 08-10-2009, 22:13   #9
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This is what they list for the mini 14

"Calibers available @ this price. .223 Rem., .222 Rem, .204 Ruger, 6mm X .223, .17 Rem. Others call for pricing. "

The catch all MIGHT be the "others call for pricing" part. But if you look closely on this page http://www.ruger-mini-14-firearms.co...ini_prices.php you'll see the other calibers arelisted for mini 6.8 and mini 30 conversions.
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Old 08-11-2009, 06:29   #10
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Originally Posted by jimbobborg View Post

Weird thing, I believe that the 6.8 magazine well is bigger than the .223 magazine well. At least according to ATI. Why is it weird? I have an AR that I'm building in 6.8 and the 6.8 marked magazines fit in the standard .223 magazine wells. IDK what Ruger was thinking.
I'll speculate that Ruger wanted a 5rd mag to fit flush with the bottom of the rifle for the larger 6.8 SPC cartridge (like the Mini Thirty), so the mags (and mag well) are slightly wider in the rear versus the .223 (again, like the Mini Thirty).
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Old 08-11-2009, 08:11   #11
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I'll confirm that. When I converted a .223 wooden stock to fit my 6.8, the magazine area had to be widened and the metal reinforcement stretched wider to accept 6.8 magazines. John
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Old 08-11-2009, 08:36   #12
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Originally Posted by MINI SSS View Post
I'll confirm that. When I converted a .223 wooden stock to fit my 6.8, the magazine area had to be widened and the metal reinforcement stretched wider to accept 6.8 magazines. John
The stock reinforcement frame for the Mini Thirty works better (versus the .223 frame) for the Mini 6.8 SPC.
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