AR-15 SPR build - Lego or voodoo?

[A-Game]

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.

I echo GI comments.

My Personal Accuracy equation: your mileage may vary.

Stiff barrel with good barrel harmons, even heat treatment, clean rifling, SAMMI spec chamber, polished, heavier profile, flutes are a nice touch to disperse heat and shave a few ounces. A chrome lined barrel will increase in accuracy overtime.
A light crisp trigger with minimal take up
A clear, crisp optic
A tight fit between upper and lower doesn't matter as much as you think. Milspec is sufficient.
Tailor ammo to your rifle. Reload. Uniform, concentric, consistent sized brass, concentric primer pocket, annealed, I haven't shot enough resized brass to determine if new vs once shot makes a difference.
Fundamentals, train, read bungholes from bipods, take a couple classes, shoot thousands of rounds.

I'm sure I'm forgetting some things but the jist is don't focus on tiny details that may or may not make a difference and skip basics that are proven to work.

[John A.]

A chrome lined barrel will increase in accuracy overtime.

Chrome lined barrels are not known for their "accuracy", and other than smoothing it out in the first hundred or so shots during break-in if there are any imperfections or excess buildup in spots, will also degrade in whatever accuracy they have faster than a non-chrome lined barrel will because it's well known that even in as little as 5000 shots, have already began cracking and flaking.

Chrome lining was added for nothing more than corrosion resistance, not to increase accuracy.

There is a reason why the M24 and many other professional sniper platforms are NOT chrome lined, and I cannot think of any target competitor who uses a chrome lined barrel in competition. The vast majority of them are going to be stainless.

[A-Game]

A chrome lined barrel will increase in accuracy overtime.

Chrome lined barrels are not known for their "accuracy", and other than smoothing it out in the first hundred or so shots during break-in if there are any imperfections or excess buildup in spots, will also degrade in whatever accuracy they have faster than a non-chrome lined barrel will because it's well known that even in as little as 5000 shots, have already began cracking and flaking.

Chrome lining was added for nothing more than corrosion resistance, not to increase accuracy.

There is a reason why the M24 and many other professional sniper platforms are NOT chrome lined, and I cannot think of any target competitor who uses a chrome lined barrel in competition. The vast majority of them are going to be stainless.

John,

I want to clear up a few things...the internet and rumors really make the waters murky.

There is a reason that every 5.56 military barrel is chrome lined.

This is an AR-15 SPR subject not a F-Class rifle. Both the FN SPR and Sako TRG bolt action rifles use chrome lined barrels and they are widely known to be 1/2 MOA bolt guns. Barrels rated to 15,000 rounds instead of the usual 5,000-8,000 from non-chrome lined barrels. So the notorious accuracy loss is not noticeable in the semi automatic AR weapon system. Chrome lining a barrel does remove the sharp edge in the rifling.

I have never read a study that showed the threshold is 100 rounds for increased accuracy...you got me there. A poor quality barrel usually has poor quality chrome where as a quality barrel has better quality chrome.

The military started to use chrome lining is to extend the life of the barrel. Throat erosion is the main cause of accuracy degradation in barrels due to incredible heat and 50,000psi of pressure on the leade every time the trigger is pulled. Chrome is more heat and pressure resistant than steel. Chrome is excellent for corrosion résistance but can still rust due to neglect. Chrome lining makes for exceptional cleaning in a barrel compared to non lined bores and chambers.

Yes, poor quality barrels can see an accuracy drop after 5,000 rounds of sustained fire. Hi-power shooters will change a barrel out every 10,000 rounds or so but they are pretty obsessed with throat erosion. NOW, speaking in this situation...I would be surprised to see a quality chrome lined quality barrel shot out in less than 20,000 rounds. If you have the money to shoot 20,000 rounds in a few years then you have a few hundred bucks to drop on a new barrel when accuracy drops off, make your money back and you are back in business.

I have seen a few SCARs that have had some slight flaking of chrome...they still shoot as accurate as a Remington 700 hat doesn't have a blue printed bolt, trued action ect.

The M24 was a 6,000.00 weapon. It was a .308 not a 5.56, the 5.56 SPR was not a 6,000 weapon system so I really don't see how that applies here.

I have one rifle with a nitride 4150 barrel and another with a 11595E Certified chrome lined barrel. I cannot notice a difference in accuracy on paper. The other items I listed have a greater impact on accuracy than chrome vs non chrome. I used to be of the opinion that nitride was the bees knees and what to have in a non stainless barrel. The last year working in the industry has changed my opinion due to research, and experience shooting hundreds of barrels, measuring throat erosion and muzzle erosion on hundreds of barrels and shooting barrels that have been in combat from 3 different continents.

The specific accuracy from chrome lined barrels increasing overtime were from machine gun barrels and it was more than 100 rounds. My bad for not being more specific on that

[golfindia]

A chrome lined barrel will increase in accuracy overtime.

Chrome lined barrels are not known for their "accuracy", and other than smoothing it out in the first hundred or so shots during break-in if there are any imperfections or excess buildup in spots, will also degrade in whatever accuracy they have faster than a non-chrome lined barrel will because it's well known that even in as little as 5000 shots, have already began cracking and flaking.

Chrome lining was added for nothing more than corrosion resistance, not to increase accuracy.

There is a reason why the M24 and many other professional sniper platforms are NOT chrome lined, and I cannot think of any target competitor who uses a chrome lined barrel in competition. The vast majority of them are going to be stainless.

Uh, please fix this quote. Golfindia did not write this....

[John A.]

A-game, my reference to ~100 shots is typical break-in period.

Sorry that I was so vague. But when a barrel is new, if there are any inconsistencies in the lining or burrs or whatever, usually are smoothed out relatively early on in the barrels life and was the only reason why I threw out the 100 shot number.

I wasn't trying to imply anything magical.

But in many ways, you are absolutely correct. If you start out with a good barrel, with known good quality, you will often have a good barrel through the life of the barrel. Start out with poor or unknown quality, and you may be very disappointed.

The SPR was made for squad marksmen, and why I feel that accuracy is paramount, over all else if making one to hold true to what they were.

And it used a 1:7 twist, 18 inch stainless steel barrel, and to my knowledge, were never chrome lined.

As for the scar, I've never been inside of one to inspect the barrel or anything. I do however have an old Imbel Fal upper (well before Bush stopped imports of "certain" parts), and there is more wear in the chamber chrome than anywhere else where the lining is concerned. But it still shoots exceptionally well. I can hit snuff cans at 100 yards with it pretty easily. But as I said, the chamber is noticeably worn. It'll even close on a no-go gauge. Barely, but it will. Still some life left in it though because it won't close on a x51 Max gauge and yes, I have checked obviously.

[John A.]

Uh, please fix this quote. Golfindia did not write this....

Sorry about that.

I did fix it in my earlier post.

[A-Game]

I'm a perfect world right?!

[triggerman300]

My last SPR build consisted of Aero Precision Enhanced upper and Gen 2 lower with a Ballistic Advantage 18" premium barrel in 223 Wylde. MagPul stock and grip with a Rise Armament 3.5# trigger. All this under a Primary Arms 4-14 scope. With my handloads of 55 gr Ballistic Tips or 77 gr SMK it will shoot under 1" at 200 yds almost every time. The only thing I really cheaped out on was the $25 ebay 3 chamber muzzle brake. No voodoo here,just quality parts assembled with care.

[wildfowler]

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.

I wonder if anyone has ever tested this.

A non glued rifle build that also happens to be a non-shooter that improved after being taken apart and glued? Or vise versa?

I'm not sure how you unglue a good shooter to test though?

[triggerman300]

I've seen people come unglued,it aint pretty!