AR-15 SPR build - Lego or voodoo?

Discussion about 5.56mm ARs

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DutchV
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AR-15 SPR build - Lego or voodoo?

Post by DutchV »

I'm planning to assemble an AR upper for an SPR style rifle. I've got tools, a vise, receiver block, etc. Fanboys and celebrity trainers will say that only their favored company can make an accurate rifle. (But we should ignore the payola and free shirts). I don't believe it.

So what goes into an accurate build? Obviously you have to start with a good barrel and decent parts. I've got a Black Hole Weaponry barrel, PSA Premium BCG, and an Aero Precision enhanced upper & free float combo.

I know about using Loc-Tite to bed the barrel extension to the upper, and truing (or lapping) the face of the upper receiver. Aero says lapping isn't needed for their upper, so I'll skip it.

Are there any other assembly tricks you guys like? I know some of you prefer to roll your own.

Thanks, Dutch
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John A.
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Re: AR-15 SPR build - Lego or voodoo?

Post by John A. »

I do prefer to build my own.

But you totally lost me here:
I know about using Loc-Tite to bed the barrel extension to the upper,
I have never glued a barrel to an upper, nor do I see the logic or point of it. Even if trying to squeeze another 1/4 moa out of it.
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DutchV
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Re: AR-15 SPR build - Lego or voodoo?

Post by DutchV »

John A. wrote:I do prefer to build my own.

But you totally lost me here:
I know about using Loc-Tite to bed the barrel extension to the upper,
I have never glued a barrel to an upper, nor do I see the logic or point of it. Even if trying to squeeze another 1/4 moa out of it.
It improves the consistency of the fit between the barrel and the upper. Some guys will turn down their own barrel extensions to get a tight fit. Many of us do not have a lathe handy so Loc-Tite gets the nod. JB Weld is also used. Paste wax or shoe polish will serve as a mold release to keep it from becoming a permanent bond.
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smustian
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Re: AR-15 SPR build - Lego or voodoo?

Post by smustian »

John A. wrote:I do prefer to build my own.

But you totally lost me here:
I know about using Loc-Tite to bed the barrel extension to the upper,
I have never glued a barrel to an upper, nor do I see the logic or point of it. Even if trying to squeeze another 1/4 moa out of it.
I have read about high accuracy builds having green loctite used when seating the barrel into the upper receiver. Theoretically you want a barrel and upper receiver to have as tight a fit as possible but most are not. The loctite "seals" the fit between the two taking out any chance of wobble.
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John A.
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Re: AR-15 SPR build - Lego or voodoo?

Post by John A. »

Thanks for the explanation. I understand about bedding actions and such, but that doesn't seem to make me believe that it would make the gun more accurate.

To me, accuracy comes more from the barrel and the ammunition and the shooter technique than anything and gluing the steel barrel to the aluminum receiver at best would just seem to introduce more vibrations and harmonics due to the physical joining of the parts, if not anything else than due to the movement from the bolt and the buffer/buffer spring movement.

I guess this is one of those times where I just grin and nod and say OK.
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Re: AR-15 SPR build - Lego or voodoo?

Post by tfbit »

I'll recommend a heavier barrel. I've shot a clean run on plates, in a multi-gun match, from 200-450 yards with my Daniel Defense 16" barrel. It regularly shoots MOA groups. I haven't seen quite the accuracy from my AAC lightweight 16" barrel. I know a few other people here are very happy with their DD barrels also.
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golfindia
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Re: AR-15 SPR build - Lego or voodoo?

Post by golfindia »

If you really want a permanently fused non wobbly barrel and upper, just clean the upper and extension well and put them together dry.

I put plain old axle grease on the extension and nut threads because they are dissimlar metal joints, and I've taken apart enough dry ones to know what happens at that dissimilar metal joint.

I think heavier barrels are more accurate, anectodally, because i think more heat dissipation makes for a cooler barrel, and a cooler barrel is more accurate barrel. JP enterprises seems to align with this rationale as well, considering that radiator doohickey they put on their precision rifles.
DutchV
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Re: AR-15 SPR build - Lego or voodoo?

Post by DutchV »

The barrel I have is 1.0" diameter behind the gas block, and slightly less than .750" in front of it. Heavier is not attractive since I might actually carry it, unlike a varmint rig that would stay near the truck.
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DoubleJ
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Re: AR-15 SPR build - Lego or voodoo?

Post by DoubleJ »

The second AR I did was an SPR clone. I had no idea what I was doing, watched mad youtube videos about assembling parts, used all quality, but not insano expensive, stuff. Rifle shoots about 3/4 MOA with good ammo and me having a good day. Managed a 3.5" 3 shot group at 500yds once, and I'm claiming it. Here's what I made it from if I remember right:
Aero stripped upper and lower

Magpul STR
Larue APEG
H2 buffer on a Tubb spring
Geiselle SSA-E
Accu wedge (PITA to split the halves now)

Rainier 18" match HBAR 1:8
FailZero BCG (Old, good one)
PRI brake
Troy 15" alpha rail
Harris bipod
Burris PEPR mount
Vortex PST 2.5-10

Didn't do anything special when I assembled it, just some axle grease on the barrel nut.
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Re: AR-15 SPR build - Lego or voodoo?

Post by Jakal »

I would say buy the best trigger you can. You'll get more accuracy out of a suped-up trigger over a standard GI trigger.

Quality optics, if you are older. The older I get, the better optics are needed. Long gone are the days of using a low end Tasco. Now its a minimum ~$500.00 for glass. Best scope I have is a Ziess Hd5 5-25×50. Couple other Ziess, Monarch III XRT and a few EOTechs. Then the midrange Millett, Bushnell, Simmons and Weaver. $200-400.
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