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Old November 12, 2011, 02:27 PM   #1
GI Sandv
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Location: Minnesota
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AR Build: barrels and caliber questions.

Like everyone else these days, I'm interested in building an AR. If I stick with the standard platform setup, I'll likely go with 5.56 since, as I understand it, they have a higher SAAMI rating and fit both rounds better (whereas a .223 barrel won't fit a 5.56?). However, I've read a little bit about the newer 6.8 SPC round and am curious about that. In all, I'm looking for something similar to the M4 I carried for 15 months in Iraq but ideally a little nicer. This would be used primarily for plinking. However, I would like it to be suitable for small game and, if using the 6.8 SPC barrel, maybe deer?

My primary questions are (and feel free to let me know if I've missed other significant and related considerations):

1) What do I need to be concerned with in barrels, both length and rifling? I'm thinking of something in the 14" range. What type of accuracy can I get with that at 300, 400, 500 yards?

2) What should I consider when buying an upper receiver. I don't worry about build quality with the lower so much, but I'm willing to spend more money if necessary to get a high-performance, durable upper. I'm not using this for match so quarter-sized shot groups at 100+ yards are not my primary concern. I would rather put money into durability and quality of internals, rather than externals that look like they came out of a new XBox game. What's the bottom line on a good, quality upper? (This is one I've considered, although twice as expensive as some more "standard" ones.

3) What about swapping this out with 6.8 SPC rounds? I believe if I were to move up to a .308 barrel, I'd have to get a new upper altogether, no? However, my understanding is that 6.8 is interchangeable, just needing a new barrel and bolt (assuming the whole bolt carrier assembly, or is it just the bolt itself?). I know that buying a separate upper kit and having sights mounted on that would make swapping this out immeasurably easier and would avoid having to resight every time I swap out the barrel. However, as it stands, I don't have the money for this whole rifle right now. I'd like something I can use year-round, for amusement and varmint hunting most of the time, then swapping out the 5.56 for the 6.8 during deer season. Although more complicated, is this a feasible option?

4) Although not related to the upper build, I'm curious about triggers. My service M4 had a horrible trigger (although I didn't realize it at the time). I have a Kahr MP4 as my every day carry and have grown to love the trigger on that. (It's a fairly long, very smooth but somewhat heavy DAO.) Do they make similarly smooth triggers for M4/ARs for less than $150? I might forego the nicer trigger for now and just stick with factory for the time being. But if I can get into a nicer trigger for $150 or less, I might.

As I said, these are my primary concerns. However, if there are significant issues with my underlying assumptions, I would love to hear criticism of that as well. Thanks.
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Old November 12, 2011, 02:58 PM   #2
DnPRK
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1. A 14" barrel is a NFA item that requires Federal approval as a short barreled rifle, with extra paperwork and fees involved. There is no such restriction for a 16" barrel.

The specifications for your service rifle and ammo were very tightly controlled to assure reliability and accuracy. There are no such spec controls for commercial-built rifles. That said, put your money into a quality barrel, ammo and magazines and you will get the reliability and accuracy you seek.

2. There are many expensive boutique uppers available on the commercial market, but they don't perform any better than run-of-the-mill uppers. Bravo Company has a good reputation for quality products and excellent customer service if you have a problem.

3. The easiest caliber change is to purchase a complete 6.8 SPC upper and magazines and swap them to your existing lower.

You are correct that 308 is not swappable because it requires a larger upper, lower and magazine due to the larger size of the cartridge.

4. The commercial market has many good options for triggers. The best are by Geissele in adjustable (DMR) and non-adjustable (SSA) models.
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Old November 12, 2011, 03:06 PM   #3
Jim243
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Quote:
I'm thinking of something in the 14" range
As long as you were USA property that was OK, but here you need to go 16 inch to be legal, unless you are willing to go throught getting it classed as a Short Barrel Rifle through the BATF.

For trigger I would recommend the RRA two stage match trigger.

http://www.rockriverarms.com/index.c...ategory_id=294


Jim
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Old November 12, 2011, 05:00 PM   #4
blacksky
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6.8mm or 6.5 variants

6.8SPC is a decent round compared to 5.56 but severely overshadowed by 6.5G in every regard. Facts are solidified by testing and proof. Now, originally I was a advocate of the 6.8SPC and nothing could change my mind because when compared to 5.56 is offers more energy at most any range. And although 5.56 is bashed a lot, it is a decent round as I've done many of my own ballistic tests at varying distances on various objects and materials and have been surprised at what it can do.
The US Military will basically never swap out the 5.56 M4, M16, and their variants for another cartridge size. Accept it. Do they need to? Yes, absolutely. Ask anyone who's been to Iraq...Ok, not anyone but those with actual real experience. They will tell you that it is not all CQB distance engagements and many times they were shooting their weapons at ranges of 800m or more with no clue if they could even reach out that far and do any damage. At that distance (800m and beyond) the 6.5G starts to outpower and range even the 7.62 nato and depending on the round...is still supersonic out to 1300 yards. A round that is supersonic at that distance will absolutely have plenty of CQB power. Try shooting a human size target at 800m+ with an M4 with a Red Dot or better yet...Iron sights. ACOG, not as bad.
Now look at ballistic charts of the 6.8 in comparison to 6.5G and 7.62N. The 6.8 falls like a ton of bricks and loses it's steam very fast. It has absolutely horrible ballistics when it comes to range and energy. And if you think your enemies are always going to be in close quarters then you just don't live in a real world.
Also please take note of the Accuracy of the 6.8SPC round as it also heavily lacks compared to 6.5G. Every type of test has been done and not in one of the tests did 6.8SPC outperform 6.5G. Or just build another 5.56 as parts, ammo are more readily available and affordable...

My most recent builds...

http://thefiringline.com/forums/showthread.php?t=467440

http://thefiringline.com/forums/showthread.php?t=468190
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Last edited by blacksky; November 12, 2011 at 07:21 PM.
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Old November 12, 2011, 07:15 PM   #5
Eghad
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You can get a 14 inch barrel and install a non removable flash suppressor that gets it past the 16" length

or the 14 " is going to cost you some paperwork and a $200 tax stamp.
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Old November 13, 2011, 01:26 PM   #6
GI Sandv
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6.5G, 14" Barrel

Well, I had not realized that a 14" barrel would be a problem, so I suppose that's no longer a consideration.

As to the 6.5G rounds, it sounds like a better option. Has anyone had any experience a) finding bolts and barrel for this round and b) buying this ammunition. I'm not familiar with this ammunition at all and so wonder how practical it is to invest in this type of project. I did find a custom manufacturer in Iowa and while their prices were not unreasonable, were more than I would like to spend. If this is the best option, I may just have to wait on the alternate barrel set up and stick with 5.56 for now.

Also, has anyone had any experience with 5.56/.223 deer rounds? I know larger calibers are usually recommended for deer. However, I have read that there are some good, premium .223 rounds out there. Can anyone verify this? I would probably only be using these for smaller doe--the tags are easy to come by here in Minnesota--and not on larger bucks.

Thanks again.
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Old November 14, 2011, 03:49 PM   #7
tirod
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The alternate calibers for AR15's can be more powerful, longer ranging, offer more precision, or more lethality, but in no way is one flatout "overshadowed in every regard." That's BS fanboy talk, and completely unsubstantiated.

Why? Because there in NO final authority or definitive characteristic that forces one or the other into an "inferior" position. The first problem is defining exactly what numerically definable quality could be measured - and what priority any one shooter would give it.

A long range distance precision cartridge does not necessarily "rank" higher - if so, would the .300 Win Mag outclass the 6.5G? Where then does the .50BMG fit? Especially when it's shot from a 14.5" carbine set up for CQB, or a 12" with suppressor?

Define what range, what target you intend to do most of your hunting for, then choose what cartridge meets the task. Too many shooters pick a cartridge and then force it into operation where it was never intended.

If you want to have the ballistic performance of each potential cartridge and it's application explained, got to that specific cartridges forum site and read the stickies. Check Wikipedia, read up on the initial developement, find out for yourself why the designer came up with it and what they intended to do with it.

Note carefully - any time alternate calibers come up, posters go out of their way to say that their favorite is "better" than 6.8. Obviously, they have to compare it to something that is apparently the defacto standard of power and performance in order to say their's is "better."

"Better," how? Only by their standard. It's up to you to decide if what somebody else wants even fits what you need.

There's no guarantee a cartridge does anything you want until you understand what YOU need it to do - then you can decide whether it meets the need, or a different one does.

What kind of hunting is being done? If it's on live game, and generally under 450m, it's far more common to see 6.8SPC being used. And it's far more common on the market, too. If the amount of guns, loads, and happy hunters has a point, it's quite successful.
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