6.8 SPC vs. 7.62 Question
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Ratdog68
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If you're considering a 6.8 SPC in a Ruger Mini-14... I'd consider other options.
1. Ruger chambers in the SAAMI spec, NOT the 6.8 SPC II chambering
2. Ruger uses a faster twist rate than the preferred 1:11-1:12
3. Ruger Mini-14s are not exactly known for their good accuracy
With the incorrect specs and faster twist rate barrels, excessive pressure will be generated with some factory loads, as well as warmed up hand-rolled ones. I'd suggest you go with a vendor of an AR platform who is up to date on the barrel/chamber spec requirements.
I'm not plugged into the Mini-14 platform so well... I don't know who all makes mags for Rugers.
Al LaVodka
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7.62x51/.308 should be your choice it seems fairly obvious to me.
To compare it to the dopey inaccurate x39 ammo and its usual platforms is unwarranted. And putting the average x39 in an AR platform is a silly waste as well. The x39 ammo is cheap. Not just inexpensive. Cheap. Inaccurate inherently.
I'd also wait till NATO adopts the 6.8 SPC (the modernized .276 over which we kept the .30-06 and replaced that with the 7.62x51) which is a great idea, in theory.
Al
To compare it to the dopey inaccurate x39 ammo and its usual platforms is unwarranted. And putting the average x39 in an AR platform is a silly waste as well. The x39 ammo is cheap. Not just inexpensive. Cheap. Inaccurate inherently.
I'd also wait till NATO adopts the 6.8 SPC (the modernized .276 over which we kept the .30-06 and replaced that with the 7.62x51) which is a great idea, in theory.
Al
Maverick223
Member
No, it is not. Most factory cartridges are not good loadings, but there is no such thing as an inherently inaccurate cartridge. The 7.62x39mm is a very efficient case, that feeds exceptionally well, and can be loaded just as accurately as any other cartridge. It is limited in effective range, and has a rainbow trajectory, but that doesn't mean that it is inaccurate, not by a long shot. Keep in mind that the 7.62x39mm is the parent case for .220Russian, which is the case for the 6mmPPC; most folks don't find the PPC to be deficient in the accuracy department. You can load the 7.62x39mm to be just as accurate...just ask Krochus about it.
Rokman
Member
Ratdog68, it's good to see that you finally got your 6.8 carbine together. Let us know how it works. I talked to the folks at AR performance awhile back, and they seem to be good people.
Float Pilot
Member
I have been playing with the 6.8x43mm for a couple years now...
It is better than a 5.56mm, but not as good as a 7.62x51mm. One is a rifle round, the other a carbine round. End of story.
It is better than a 5.56mm, but not as good as a 7.62x51mm. One is a rifle round, the other a carbine round. End of story.
Ratdog68
Member
Maiden Voyage
Harrison and Donna are good folks to deal with. He builds a FINE upper.
Otay... learned a few things yesterday. Between the coatings on the lense of the reflex red dot optic (with no magnification), the polarization of my Rx sunglasses, the red dot over a SMALL orange target dot at 50yds, and my 50yr old eyes... it's nearly impossible to bead in on those orange stick on dots. So... gonna have to make some changes to how I shoot with this rig. Probably gonna have to lose the polarized Rx sunglasses and stick with "clear", get some "black" stick on dots that are a LITTLE bigger than these and give it another try another day. 'Course... the shoot a couple, clean the bore, shoot a couple more, clean the bore routine sort of breaks up your concentration a little bit too. All in all though... I was "on the paper" with my second shot, and dialed it on over 'til I was in there fairly close.
I'm gonna have to tinker with the mesh bag brass catcher. It shifted on my third shot and an empty didn't clear the ejection port and buggered the mouth of the empty. I'll deal with it another day... too many other things to concentrate on. Other than that... everything fed and ejected just fine. I think it was kicking more to the 2:00 position, but, not gonna worry about that until it's broken in. The SSA 110gr Sierra Pro Hunters functioned just fine. I only loaded five rounds at a time in my 25rd C-product mags... it cycled as it should and locked open after the last round was ejected.
Gettin' ready to shoot 'er for the first time !!! Temp was 59F, wind was ENE @ 5mph, shooting northward. Basically, sea level and 75% humidity.
40rds of ammo... Check. Tactical Twinkie... Check.
The new dust covers be fine there H.
You'll find 39rds on the paper... the first one was a bit too far left.
This string was the "get it close" while pausing to clean between every couple of shots
The next one was a 3shot group to finish the clip
The rest of them are 5 shot groupings in order of their being shot.
Harrison and Donna are good folks to deal with. He builds a FINE upper.
Otay... learned a few things yesterday. Between the coatings on the lense of the reflex red dot optic (with no magnification), the polarization of my Rx sunglasses, the red dot over a SMALL orange target dot at 50yds, and my 50yr old eyes... it's nearly impossible to bead in on those orange stick on dots. So... gonna have to make some changes to how I shoot with this rig. Probably gonna have to lose the polarized Rx sunglasses and stick with "clear", get some "black" stick on dots that are a LITTLE bigger than these and give it another try another day. 'Course... the shoot a couple, clean the bore, shoot a couple more, clean the bore routine sort of breaks up your concentration a little bit too. All in all though... I was "on the paper" with my second shot, and dialed it on over 'til I was in there fairly close.
I'm gonna have to tinker with the mesh bag brass catcher. It shifted on my third shot and an empty didn't clear the ejection port and buggered the mouth of the empty. I'll deal with it another day... too many other things to concentrate on. Other than that... everything fed and ejected just fine. I think it was kicking more to the 2:00 position, but, not gonna worry about that until it's broken in. The SSA 110gr Sierra Pro Hunters functioned just fine. I only loaded five rounds at a time in my 25rd C-product mags... it cycled as it should and locked open after the last round was ejected.
Gettin' ready to shoot 'er for the first time !!! Temp was 59F, wind was ENE @ 5mph, shooting northward. Basically, sea level and 75% humidity.
40rds of ammo... Check. Tactical Twinkie... Check.
The new dust covers be fine there H.
You'll find 39rds on the paper... the first one was a bit too far left.
This string was the "get it close" while pausing to clean between every couple of shots
The next one was a 3shot group to finish the clip
The rest of them are 5 shot groupings in order of their being shot.
Wesson Smith
Member
Man, I love this place, but it's threads like these that nearly sink me into a state of depression. Early last winter I ordered a 6.8 upper from LMT and put it together with a Rock River lower. I thought I had a pretty sweet package from a reputable (LMT) manufacturer, and now after reading this it would seem that I have an inferior setup. The LMT is a 1:10 twist, and I guess that's not good enough? I won't even go into the SAAMI vs. spec 2 debate. My setup shoots SSA ammo just fine, and is quite accurate. What am I supposed to be experiencing? Bullet destabilization? Diminished ballistics? Excessive chamber and/or barrel wear? I'd sure appreciate some clarification before I lug my "useless" rifle to the pawn shop!
Ratdog68
Member
My understanding of the twist rate is... the increased friction of a faster twist rate and a 6 lands/grooves takes away from the muzzle velocity potential from a given charge, simply a minor decrease of effective range for a given recipe... not much else. Original offerings of the caliber were made using the .270 barrel stock, thus the 1:10. The spec sheet with the diagram which went to SAAMI (as I recall the tale), two numbers were transposed at some point and SAAMI gave their blessing to the incorrect spec. This netted a leade of too sharp of an angle. The result... higher than ideal chamber pressures, and a requirement to tone down the ammo... thus, SSA has "Commercial" and "Tactical" offerings. A SAAMI spec'd chamber is in danger of bad things happening if shot with the "Tactical" (Hot) loads. I don't know what LMT offers for their chamberings... but, you can have it reamed to the SPC II spec, which basically changes the leade and gives a preferred 45 degree angle. The newest offerings are also responding well to having the M4 feed ramps too... easily done as an upgrade if ya don't have them. The weak link in handrolling your own for this caliber (with the SPC II chamber) is that your COAL is limited by what the magazine will allow for feeding... no way around this since the 6.8 round needs to feed from a magazine that fits into a 5.56 magwell. It is what it is. The SAAMI spec'd chamber adds an additional handicap for loads... the incorrect leade requires the projectile to be seated even further into the neck of the casing... meaning, the need for a milder load.
If you have SPC II and a 1:10 twist, don't sweat it... your rifle should serve you just fine... all you're giving up is a small amount of muzzle velocity.
Wesson Smith
Member
Wow, thanks for the informative and detailed reply. Much appreciated.
Now for a dumb question: How can I tell if I'm SPC spec II or not? Since a lot of LMT's manufacturing process is "proprietary" should I give them a ring and to see just exactly what I'm dealing with?
Now for a dumb question: How can I tell if I'm SPC spec II or not? Since a lot of LMT's manufacturing process is "proprietary" should I give them a ring and to see just exactly what I'm dealing with?
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Ratdog68
Member
I'd start with a call to them. Hopefully they'll know (ya never know who's gonna answer a phone these days). If you don't get an answer there... you could try a couple of other approaches to find out. If you called Silver State Armory ("SSA") to inquire whether their "Tactical Loads" will work with your make of gun, they MAY or may NOT have an idea (and, may or may not WANT to give an ok too). Another approach is... there's a LOT of guys on the 68forums.com that would have more knowledge about the history of which makers offer(ed) what. As a last resort... have someone ream it to SPC II and if it isn't already, it will be afterwards.
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