My 7mm AR-10 Build (In Progress)

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Synchronizor
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My 7mm AR-10 Build (In Progress)

Post by Synchronizor » Sat Jan 06, 2018 8:38 am

Just took delivery of this today, an Aero Precision M5 lower receiver and lower parts kit. This is intended to become the core of a 7mm-08 AR-10 build (and yes, I know the Aero receivers are DPMS .308 pattern, not genuine Armalite AR-10 pattern, but it's a sized-up AR that shoots a .308-derived cartridge, so I'm calling it an AR-10).

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This is a project that I've been thinking about for quite awhile now, reading about AR builds and bookmarking parts & manufacturers that I came across & liked. I ended up with a little more free money than usual thanks to some Christmas gifts, and when I saw that Aero had a good sale going, I decided to pull the trigger and kick things off.

This'll probably be a pretty drawn-out build; one major component at a time as I research things & make up my mind, and as funds allow. The planned end result is a really high-end AR-10 with a lot of nice features (perhaps even multiple uppers for different applications), so each step is probably going to be fairly expensive, and the final price tag will probably be intimidating. If I get impatient, I may end up throwing in cheaper alternatives for some things temporarily, and upgrade down the road, but I'd prefer to do things right the first time as much as possible, and avoid paying for parts that end up unused.

Anyway, the project has now begun, and I'll update this thread as things progress. Feel free to share input or recommend any AR parts & accessories you've had good experiences with.

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Re: My 7mm AR-10 Build (In Progress).

Post by Scorpion8 » Sun Jan 07, 2018 6:20 pm

Synchronizor wrote:
Sat Jan 06, 2018 8:38 am
This'll probably be a pretty drawn-out build; one major component at a time as I research things & make up my mind, and as funds allow.
I applaud you. In my garage is a box full of AR-10 components also, which has been there (as you say) for a drawn-out build. Except mine will be .308, the true caliber of all main battle rifles. I'm not a prepper, but I do have some stuff stored away in a SHTF scenario and this would be the best stopper since my dreams of owning or building a CETME or FAL aren't progressing very well. :mrgreen: What made you choose 7mm-08?
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Re: My 7mm AR-10 Build (In Progress).

Post by John A. » Sun Jan 07, 2018 6:35 pm

Nothing wrong with the 308 at all.

The only 308 that I own is a (preban) Imbel Fal. It was built just before Bush's import ban and other than the receiver itself and the full auto trigger configuration, is otherwise all surplus import.

Mine is exceptionally accurate with certain ammunition.

I can hit snuff cans and pop bottles at 100 yards effortlessly. Many think the Fal's are not very accurate, but I wouldn't hesitate to use mine for that role. Though would be far too heavy to hump around all day with. https://www.youtube.com/watch?v=u0afXlnHcio
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Re: My 7mm AR-10 Build (In Progress).

Post by Synchronizor » Sun Jan 07, 2018 9:55 pm

Scorpion8 wrote:
Sun Jan 07, 2018 6:20 pm
What made you choose 7mm-08?
A big part of it was just wanting to do something a little different. But also, I think the 7mm/.284 caliber is a real sweet spot when it comes to short-action rifles, especially if one is willing to handload, which I intend to do.

Nothing at all wrong with the .308; it's a great all-round, well-balanced cartridge that's relatively economical to shoot, easy to find, and gives a ton of options both for reloading and off-the shelf. I have a friend who's just getting into target shooting with a bolt-action, and I recommended the .308 to him without hesitation. However, comparing 7mm-08 & .308 loads with bullets in the 145 - 155-grain range typical of .308 service loads, I've found that the two cartridges have very similar muzzle velocity potential, but the more slender 7mm has a distinct BC edge. Just flipping through one of my Hornady reloading books, I'm seeing mid-weight 154-grain .284 hunting bullets that have BCs equivalent to 178-grain .308 match bullets; and to match the form factors of some of the 162-grain .284 match bullets, a .308 projectile would need to be over 200 grains, which cannot be pushed nearly as fast when you're working with a .308-family case capacity.

Of course, that naturally leads the conversation to the .264 caliber, which for an AR-10 would be the 6.5 Creedmoor (or the .260 Remington, but the Creedmoor is the current hot thing with a lot of nice factory loads and off-the shelf barrel options). Again, great round; there's a lot of smart people, a lot of good math, and a lot of tiny groups that can attest to the ballistics of the 6.5mm. Plus, a lot of good off-the-shelf ammo with very nice bullets. But while it may have a slight edge over the 7mm-08 for target shooting (though the real advantage with the 6.5 seems to be lower recoil for the same trajectory, but as a regular 12ga user, I'm not overly concerned about that), the .284-bore has an advantage with bullet weight and downrange energy for targets that are tougher than a piece of paper. Plus, better barrel life with the 7mm compared to the 6.5. This gun is probably going to see just as much recreational blasting as precision shooting, so better barrel life is good.

The less-common chambering does mean I have some homework to do figuring out how best to set up the upper. Barrel length & gas system length are still up in the air at this point, and I'm having a heck of a time finding a handguard that I really like for this thing. So, you're probably going to see me finishing out the lower before moving on to the upper. Next purchase will probably be the buffer tube, stock, and grip. I think I've figured out what to go with for that once I have the money, but I'd like to play with one in person if I can.

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Re: My 7mm AR-10 Build (In Progress).

Post by John A. » Mon Jan 08, 2018 12:32 am

A big part of it was just wanting to do something a little different. But also, I think the 7mm/.284 caliber is a real sweet spot when it comes to short-action rifles, especially if one is willing to handload, which I intend to do.
Sounds like an interesting build for sure. Hope to follow along.
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Re: My 7mm AR-10 Build (In Progress).

Post by Synchronizor » Mon Jan 08, 2018 4:45 am

Lower assembled with the parts kit, plus an old A2 grip just as a place-holder. I left out the buffer retainer & spring, as I intend to skip the traditional buffer & spring and use a captured buffer spring assembly, which doesn't require the retainer. Easier take-down and one less part to break.

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I have to say, I love how nicely Aero's pivot & takedown pins fit; there is virtually no discernible movement when the pins are fully in place. The Aero lower does incorporate a tensioning screw to take out slop between the lower & upper, but if the upper is as precision-made as the lower appears to be, there probably won't be much play to begin with. The use of a threaded pin instead of a roll pin for the mag catch is a nice touch as well.

The hole for the takedown pin's spring & detent is also threaded for a set screw, but for some reason neither the lower nor the parts kit include that. The pistol grip is holding the spring in for now, just like it does the safety selector spring, but two springs is a bit much to try to keep lined up when installing or removing the grip. I plan on swinging by a fastener store or two while I'm out tomorrow to grab some set screws.

However, I don't think I'm really feeling the safety selector that came in the parts kit. Kinda big, pokes my thumb in the firing position with the A2 grip, and it doesn't move all that smoothly. I'll probably swap it out down the road for something with a shorter throw and/or a smaller lever. Luckily, the Aero lower's selector markings are cleverly laid-out so that they will line up with 90- and 45-degree safety lever throws (and anything in-between).

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No rush on that though, this selector gets the job done, and it's paid for. Before I pick out & buy a fancy safety, I'll at least want the grip, stock, and trigger in place, though I'll likely wait until the gun is complete enough to fire.

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Re: My 7mm AR-10 Build (In Progress).

Post by Scorpion8 » Mon Jan 08, 2018 5:49 am

Good progress. AR's are surprisingly easy to build, and as customizable as Lego's. Not quite as easy as an AK-47/74-type, and a bit more temperamental. I've built several for different purposes, and the number of options changes and increases daily. It's an amazing segment of the gun industry.

I'm also a big 7mm fan compared to the typical 30's, but my build is meant to be able to find ammo everywhere. The .308 is almost universal. But I have quite a few 7mm hunting rifles.
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Re: My 7mm AR-10 Build (In Progress).

Post by Synchronizor » Mon Jan 08, 2018 6:27 am

If you're buying ammo off the shelf, the .308 is definitely the way to go. Factory load selection for the 7mm-08 is better than it used to be, but handloading is still needed to really bring out the full potential of that cartridge.

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Re: My 7mm AR-10 Build (In Progress).

Post by John A. » Mon Jan 08, 2018 2:51 pm

Synchronizor wrote:
Mon Jan 08, 2018 6:27 am
If you're buying ammo off the shelf, the .308 is definitely the way to go. Factory load selection for the 7mm-08 is better than it used to be, but handloading is still needed to really bring out the full potential of that cartridge.
I have found that to be true for just about every cartridge that has ever been made :lol:
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Re: My 7mm AR-10 Build (In Progress)

Post by Synchronizor » Tue Jan 09, 2018 12:18 am

True, reloading always gives you some amount of added flexibility, and the ability to fine-tune for a specific firearm, but as far as having load selections for specific applications, the .308 Winchester is pretty outstanding. Cheap 7.62x51 surplus for plinking, hunting loads for anything from gophers to grizzly bears, special low-recoil rounds for new shooters, high-quality match ammo in any number of bullet weights, frangible rounds, super-light rubber- or plastic-projectile rounds for close-range practice in populated areas, blanks, the list goes on and on. Heck, there are even a bunch of factory subsonic loads for the .308, and not just from little boutique brands, either.

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