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I have a flattop lower from a AR15 build, can I use this for a 6.8. Does it need m4 cuts? I know the answer is posted here somewhere but I didn'y find it. Thanks
What lower for 6.8
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Flattop lower? I've heard of a flattop upper. :wink: The only thing different in a 6.8 AR is the barrel, bolt, and magazines. Your upper, lower, bolt carrier, stock, trigger, handguards, and everything else will work just fine. M4 cuts are not required but very helpful for reliability and accuracy.
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What? You guys have never seen a flattop lower?? 
How do the m4 cuts help accuracy?, and thanks for the help.
How do the m4 cuts help accuracy?, and thanks for the help.
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M4 cuts help the bullet feed into the chamber. They really don't help accuracy. They keep the tip of the bullet from running into the front of the receiver if the magazine follower or spring are a little slow up front. I've never really had any problems with my AR15's but I also don't have a 6.8. So, I'm not sure if the 6.8 is more prone to run the tip into the front of the receiver. I think most problems occur with full auto feeding. In 5.56 semi auto I really don't see a need for them, but if they are done correctly I do see the added benefit of why they are there.
My $.02
SS33
My $.02
SS33
Fuzzymaster said:What? You guys have never seen a flattop lower??
They help accuracy by reducing bullet deformation during feeding.
One guy's experience: viewtopic.php?f=1&t=6454&p=54550
One guy's experience: viewtopic.php?f=1&t=6454&p=54550
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You definitely want the M4 feed ramps. The original 6.8 designers specified M4 feed ramps. The 6.8 is a thicker cartridge with a larger diameter than the 5.56 which sits the 6.8 bullet tips lower in relation to the feed ramp area. 6.8 bullets can and do impact the receiver below the standard rifle feedramps. This can deform the tips of the bullets which does directly affect accuracy. Possible feeding problems can also result from no M4 feed ramps in a 6.8.
The deeper M4 ramps catch the bullet tip and guide it to the chamber much more smoothly with less chance of deforming the bullet tips, or causing a misfeed.
Good news... If your receiver doesn't have them, they're easy to install as a do it yourself project, or have your local gunsmith file them in for a small fee.
The deeper M4 ramps catch the bullet tip and guide it to the chamber much more smoothly with less chance of deforming the bullet tips, or causing a misfeed.
Good news... If your receiver doesn't have them, they're easy to install as a do it yourself project, or have your local gunsmith file them in for a small fee.
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slight thread high jack in progress. i'm getting ready to start building a 20" 6.8 from scratch. i have a few parts already from left overs. enough to fill out a lower. the question is which lower to buy. i want a caliber correct one. that means Stag, Bushmaster or Essential. the bushy is the most expensive the essential the least with stag in the middle. the the question is not about the money but the quality. if the essential is equal to the others then no reason not to use it. but if it's not as good i'll go with one of the others. please wieght in.
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It really does go back to the saying that a lower is a lower. I have a Doublestar lower a RRA lower and a Stag lower. I can't really tell the difference in fit even swapping the uppers around.The biggest difference was in the coloration of the coating. But even that has balanced out now with continuous wiping with oil every time I clean them. A lot of people have said good things about the Essentials. At this point if you can find one get whichever one you can find.
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i would love to have a couple of LAR 6's but they are no able to be had. i want to build now not a year from now.kamojo said:
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thank you sir.
To your original question:Fuzzymaster said:
If you have an AR lower it will work with a 6.8 AR upper. It does not matter that your lower is labeled .223 or 5.56, Multi, or 6.8...as long as is is a standard AR lower (I'm sure there is a more technical term for standard...) it will work with your 6.8 AR upper.
After some heavy duty shooting at the match last weekend, I highly recommend feed ramps, but if you are not pushing a lot of rounds in a single sitting, you may be fine without them. A Dremel, a picture of what it should look like (available in another thread), and some patience will take care of the feed ramp item.
Is Flat Top a brand name? If not, I do not know what you mean by flattop lower.
Hope this helps.
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