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Posted: 4/9/2015 9:17:01 PM EDT
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Ok, I am in the dark about the 6.8 spc.
1. Do you have to have a dedicated 6.8 upper and lower? 2. If you DO, who sells a stripped receiver for the 6.8? All I have found are complete uppers. I want a stripped upper. |
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This is a good thread, but it's out of date.
http://www.ar15.com/forums/t_3_121/449200_THE_STATE_OF_THE_6_8_____JULY__2009.html |
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Quoted:
What's the advantages of the 6.5 over the 6.8? I am looking for a build with a that's not a 300 AAC. Everyone is doing those. I would call better ballistics coefficients a distinct advantage. Ever since the 6.5 Grendel and 6.8 SPC were introduced at the 2004 Shot Show, there has been ongoing –– and often heated –– debate between some members of the shooting community as to which round is "better" than the other. Following is an attempt to provide an objective evaluation as to whether 6.8 SPC or 6.5 Grendel is the superior choice to succeed 5.56mm NATO for military use, by comparing the characteristics of each round and the measures necessary to utilize these cartridges in the M4 carbine, M16 squad marksman rifle, and M249 light machine gun. THE CARTRIDGES The genesis of the two rounds could hardly have been more different. The 6.5 Grendel was conceived as a sporting cartridge, and it was designed to give the civilian AR-15 owner the capability for precision shooting at long range. Load development centered on competition and hunting rounds, which for several years were the only types of factory ammunition marketed. However, the performance potential of 6.5 Grendel caused some enthusiasts to advocate it for use by the military, and factory loadings that would be legal for combat use have been gradually becoming available. The birth of the 6.8 SPC was just the opposite, having been created as a combat cartridge for special operations, and developed specifically to provide the military M4 shooter enhanced terminal effects on enemy personnel at typical engagement distances. Because of this, a significant percentage of 6.8 SPC development efforts by commercial firms has been devoted to loadings that would be lawful for land warfare, some of which have full metal jacket, armor piercing, and hollowpoint match bullets. THE M4 CARBINE In 2006 the Army decided to pure fleet deploying Brigade Combat Teams with the M4A1 carbine in “next to deploy” order as they prepared for assignments in Iraq and Afghanistan, and special operations personnel have been using M4 variants since the weapon was adopted in the early 1990s. It was probably Delta Force operators who first reported that 5.56mm M855 Ball ammunition fired from the M4 carbine failed to reliably incapacitate enemy combatants in the intense shootouts that took place in Somalia during 1993. Similar failures were experienced a decade later during anti-terrorist and counter-insurgency operations in Afghanistan and Iraq. THE M16 SQUAD MARKSMAN RIFLE When conventional units wanted infantry squads to have a 5.56mm weapon capable of significantly greater precision than the M4 carbine, the result was the Army squad designated marksman rifle (SDM-R) and the Marine squad advanced marksman rifle (SAM-R). The squad marksman has the mission of delivering precise, direct fire support for the rifle squad out to slightly beyond the normal maximum effective range of which the typical rifleman is capable. These special purpose rifles differ from the standard M16 in that they are semi-automatic only, and highly modified to achieve match grade accuracy. THE M249 LIGHT MACHINE GUN For more general fire support, the infantry squad relies upon the M249 light machine gun. The standard M249 has a fixed buttstock which is made from a synthetic material, and the barrel is nearly as long as that of the M16 rifle. This version was originally fielded in the 1980s, but urban battlefield experience in the 21st century showed the need for a more compact weapon that would be easier to maneuver in confined spaces. This requirement spurred adoption of the M249 Para model, which is fitted with a telescoping stock and carbine-length barrel. M249 ammunition is linked into belts that are attached to the weapon in 100-round soft packs, or 200-round hard plastic containers. ANALYSIS AND EVALUATION Exterior Ballistics. The 6.8mm 115-grain FMJ bullet has a ballistic coefficient (BC) of 0.292, which is much lower than the 0.428 BC of the 6.5mm 120-grain FMJ projectile that has been tested in the 6.5 Grendel. However, at the engagement distances for which the carbine is employed, there is unlikely to be a significant difference in hit probability between the two calibers, especially considering the low-magnification optical sights used on the M4. This would almost certainly hold true with exposed-penetrator rounds like that of M855A1 ammo. The 6.8mm 115-grain MatchKing has a ballistic coefficient (BC) of 0.324, which is considerably lower than the 0.510 BC of the 6.5mm 123-grain MatchKing. At the longer ranges (out to 800 meters, in Afghan combat) for which the squad marksman rifle would be employed, the more streamlined 6.5mm projectile produces a much flatter trajectory and smaller wind drift. |
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I built a 6.8 for deer hunting. Considered the 6.5, but the incrementally flatter trajectory at long ranges isn't something many can use whitetail hunting in broken cover.
In either case, you will not find ammo for $189 per 500. Not even. Better to consider what you will actually do with the gun - what range, what target. Paper plinker on a long range course on a sunny Saturday afternoon vs dense cover flushing out game in a light drizzle. Two very dissimilar rifles results - yet both are an "AR." So, whatcha gonna shoot is the most important thing to nail down. You select the ballistic curve that matches up with most of your shooting. If it's high volume, then 5.56 is it and don't look back. You can shoot 3X more of it for the same money. Worst case situation, you might discover that .300BO actually IS what fits best. After that, you've nailed down some other important issues - the cartridge and range narrow down what barrel length, which sets the gas port location and how long a handguard or free float. That determine what kind of sights, too. A 16" 6.8 deer rifle with mid gas and a red dot is one result. Or, a 5.56 pistol with 10.5" barrel and iron sights is another. Both are effective in dense underbrush - one is better over 125m, the other is legal in both seasons in MO. If all that is wanted is to build another gun, it can be done, flip a quarter and go for it. Even one that isn't tailored to any reasonable purpose will look good in pics, impress friends, and likely sell, too. That's because so few tailor the cartridge to the job first. What they do is pick a cartridge, then try to force it to work in an application where its obviously not the better choice. Like, .300BO 800m sniper gun with 24" barrel. Then you read all sorts of defensive posts about how it can be done and why everyone should agree. Job - cartridge - barrel - gas - optic. All the rest is just the part you hang on to, and that doesn't mean it requires a stock, which is just another accessory for improving aim without having to practice as much. 
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Quoted:
If your shooting over 400 yards get the 6.5. If not get the 6.8. The 6.8 was designed for short barreled rifles for cqb out to 400+ yards. But the drop is a little more than the 6.5. Sounds like a big compromise and I honestly don't understand the logic. It's like buying a Subaru for trailing riding which it can lightly do, or buying a Jeep Wrangler for the same amount of money with a transfer case and locking differentials then rationalizing the subaru because you never plan on getting into really sticky situations. I guess what I'm saying is I don't understand why anyone would pick a cartirdge with a clear disadvantage beause it may or may not be 5% better under 300yds meanwhile the other round, which cost about the same online to build, clearly outperforms in so many other applications. To each their own. I personally know guys that consider their lr308 obsolete after building a 6.5 gren. Weight savings is a big physcological component to any rifle. |
| After intense consideration, tirod was right in his post. You have basic variables that needed to be considered. I wasn't doing that. I failed to consider motivation behind the build. I fell into that build to build trap. I fell into the "it would be cool if" trap. I thought about what I want to do with it and carbine matches are the the primary set up I want. With that in mind, staying with the 5.56 is the smartest way to go. NOW, if I want to build to sell, then the debate rages on...lol. |
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Quoted: 6.5 Grendel is what you want You have no realistic lethal advantage beyond 200 or so yards with a 6.5. Not for your average shooter. You have a very good ballistic advantage if you shoot long range. Not everybody does or can. You points are well taken, but to date it has been cheaper to build and shoot a 6.8. The 6.5 is starting to catch up. But having built both, I can tell you not everybody is best served by the 6.5. But the 6.5 is a worthy caliber. Will also point out the off the rack Hornady ammo gave my sub MOA accuracy in the 6.5 out to 300 yds. The Wolf I had that was purchased from Alexander, was absolutely horrible. I have heard others with good Wolf experiences, my personal experience with 6.5 Wolf was about 4-5 MOA, this is again one mans experience. |
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Quoted:
I personally know guys that consider their lr308 obsolete after building a 6.5 gren. Weight savings is a big physcological component to any rifle. These personal friends have surrendered their Man Cards as well (w/extra demerits for psychological malfeasance). Why choose the lumbering Grendel when they could have launched 6.5's at higher speeds from their large frames ? 6.8 SPC was the round that the mouse frame should have been chambered for since Day One....too bad no one thought of it 'til the early 2000's. |
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Quoted:
Ok, I am in the dark about the 6.8 spc. 1. Do you have to have a dedicated 6.8 upper and lower? 2. If you DO, who sells a stripped receiver for the 6.8? All I have found are complete uppers. I want a stripped upper. The 6.5 Grendel and others may have flatter trajectories with the heavier bullets, but to get there they need longer barrels. The typical 6.8 set up is a lightweight 16" barrel with midlength gas port. The good SPC2 barrel makers include White Oak Armament, Wilson Combat and AR Performance. FWIW, my 6.8 AR, with a 16" WOA barrel delivers 2640 fps with Sierra 110 grain Prohunters, at moderate pressures. - CW |
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