Frankenstein AR Build


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shaggy430
March 18, 2010, 05:25 PM
I need some advice on building two AR's uppers by parting out what I have already. Right now I have a DPMS Sportical 5.56 and I am looking to build a 6.8 SPC also. The DPMS has the sport upper without the forward assist or dust cover. I want to use this upper receiver as the basis for the 6.8. I want to use the 5.56 barrel on a standard A2 or M4 type receiver. I will use my existing lower for both, or until I can afford another lower.

The new 6.8 upper will be used as a deer rifle and the new 5.56 upper will be more of a SHTF/target rifle.

I know I will need another receiver, a 6.8 barrel, and the bolt carrier group. Anything else?

My other question is does this sound like more trouble than it is worth?

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Shawn Dodson
March 18, 2010, 05:53 PM
Unless you get a barrel assembly you'll need all the hardware to go with a plain barrel. You'll also need 6.8 magazines and tools (barrel block or receiver block, barrel nut wrench, breaker bar, torque wrench, possibly a pair of split ring pliers if you have to use a different barrel nut to achieve proper torque, moly-b grease, etc.), some additional AR parts (gas tube, gas tube spring pin, etc.).

I converted an older carry handle AR15A2 from .223 to 6.8 so I could use it as a general purpose hunting rifle. I purchased 20", 1:11, HBAR assembly from DPMS, and two bolts (a second one for a spare). I used the Colt bolt carrier. I use 5 round magazines from C-Products.

The only problem I encountered with my build was the front sight on the barrel assembly. It was imperceptibly canted to the left, which, when I first sighted in my rifle resulted in me having to adjust the rear sight almost all the way to the left. The rifle shot nice, tight groups but the uncentered rear sight annoyed me. The first time I torqued the barrel nut I used a receiver block. Thinking the receiver block may have caused my barrel to turn slightly as I torqued it, I loosened it and torqued it again using a barrel block, with no effect. I got hold of a US Army M16 armorer's manual. It instructed me to put the barrel in a barrel block and then to sight through the bore on a vertical line, lining up the vertical line between 6 and 12 o'clock in the bore, and then peer through the rear sight (in centered position) to line up the front sight on the same vertical line. This is where I discovered how much the front sight base was misaligned. I removed the taper pins securing the front sight and adjusted it to vertical (it took a few tries as the front sight based kept wanting to drift to the left as I installed the taper pins, which I offset with a few good whacks using a rubber mallet.). Once I had everything lined up I took it to the range and was pleasantly rewarded for my efforts, as the rear sight was perfectly adjusted dead center.

Good luck with your build.

RyanM
March 18, 2010, 06:15 PM
It would only be worth the hassle if you're planning on doing this often enough that the hardware pays for itself, or if you just want the experience of swapping a barrel.

Otherwise, you could probably sell the upper, buy a new one, and actually come out ahead finance-wise, compared to buying the parts and tools and selling the used parts.

Here's a like new CMMG 6.8 upper I found. No affiliation with the seller, don't know if it's still available, etc.

http://www.subguns.com/boards/under500.cgi?noframes;read=65461

In comparison, if you buy a 6.8 barrel from CMMG, with all the trimmings... holy crap, that's $561.50. Plus tools and labor. Call it about $75 for an action block and barrel wrench. Over $650 when shipping is added in, and you're supplying the upper receiver. In comparison, the complete 6.8 upper with all the same stuff (plus handguards) and all the work done for you is $610 + $24 S&H direct from CMMG. And that's only if you can't find a better deal, like the $500 upper linked.

Tirod
March 18, 2010, 08:18 PM
I always flinch when I hear the term "Frankenstein," because they all are. Nobody builds a AR from the preforged billet to the final product. They ALL buy parts from somebody else. If the purchasing department can get the upper separate from the lower and anodize both to save $10 a rifle, it's a done deal. Even Colt buys the forged platters from a supplier. Very few rifle their own barrels or have the equipment, and those that do will for others.

Right now it may be a lot cheaper to just buy an assembled 6.8 upper and go from there. If it's a cash flow situation, sure, go for it a part at a time. It's not really necessary to buy special armorer's tools if some diligent research and ingenuity is used. I'm doing exactly that. Having some to repair my own cars doesn't hurt. Some tools are only used to prevent cosmetic damage to the gun - and it may not show anyway.

Your best resource is 68forums.com, with specific info, sources, stickies, and support for the long waits that sometime come between buying, receiving, and assembling.

mljdeckard
March 18, 2010, 08:41 PM
I agree with building the lower and buying the upper. Building lowers is so easy you want to smack yourself for not doing it sooner. Building uppers will involve more specialized equipment and some trial and error. I would rather let someone else do it.

I also agree about annoyance when people sniff at home-builds because they aren't 'name brand'. You can buy a name brand one and have problems with it. I finally decided that it really only matters if you are trying to sell the rifle, and I don't plan on selling mine. Building your own frees you up to do it EXACTLY like you want it. Order the Brownell's AR catalog, it's free, you will see all kinds of options you never knew you needed before. :)

RyanM
March 18, 2010, 09:43 PM
I agree with building the lower and buying the upper. Building lowers is so easy you want to smack yourself for not doing it sooner.

I don't know, every time I've done price checking, it's looked like more trouble than it's worth. Back when I bought an assembled lower, pre-Obama-scare, let me think...

Cheapest stripped lowers were about $100. Parts kits were about $50 for a DPMS. And a mil-spec diameter stock assembly would run about $80. That's $230.

I bought a 100% assembled CMMG lower for $218.99, instead. Right now, the cheapest price I can find for a 100% assembled CMMG lower is $230. Still competitive, especially since CMMG stripped lowers, then and now, are $150 instead of $100.

Sure, you could scour boards and otherwise wait for great deals on components, but the lower I bought was in stock and ready to ship, and was at the normal price. Same for the $230 one now.

noob_shooter
March 18, 2010, 10:19 PM
http://www.midwayusa.com/viewproduct/?productnumber=375670

the part where the extractor broke scared me..

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