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With everything going on in the state of the nation, I've been very casually buying AR parts whenever they pop up at my local shop. I've been a pistol guy for over a decade, but my rifle collection has consisted of a 2 AK's and a 10-22. All plinkers over the years.
So I decided to start buying up AR parts as I found them on the internet or locally.
Over the last year, I scooped a 9.5 BCM upper in 300 BO, a Aero 12.5 upper in .556, a 16 inch PSA upper in .556 a Radian Raptor charging handle, Aero bolts, and have 2 Aero M4E1 pistol lowers, a PSA lower, a no name bolt, and just came across a Aero "rifle" lower at my local shop yesterday.
I've grabbed a few thousand rounds of 300/BO and a 1000rd case of 556 Green tips.
I've done all this without ever putting a single one together and just have a pile of parts in the closet now.

Anyways, a friend came to me and asked to buy my PSA lower and 16 inch upper, and I'm kicking it around.
I have this recently acquired Aero "rifle" lower, ( I'm assuming it's labeled that just because the tube length) and I was thinking about telling him he could have it for the cost of an Aero upper, for my rifle lower.
So here's my question
If I'm finally going to put one of these things together, with my intention being a plinker for the 1000 rounds for green tip, what length and twist should I get.
I live in a very urban area, and the only time I'd ever shoot it is out at the family farm like twice a year at most. I'd like to be able to scope it and maybe shoot out to a few hundred, let's for the sake of conversation a critter gun out to 500.
What is the recommendation for length and twist to buy?

Sorry about the noob questions, but my buddy is breaking my stones about selling it to him because he wants to own an AR with everything going on.

Thanks guys
 
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There is an optimum length for rifle barrels at which point if the barrel is any longer, muzzle velocity tends to decrease. In any words, the pressure of the burning gun powder has decreased to the point where the friction of the barrel is decreasing the bullets velocity.

The longest 5.56 barrel I've seen is a 24" barrel. Super muzzle heavy and almost had to be shot from a bench.. There are also a lot of 20" barrels out there. A longer barrel will give you greater velocity though not necessarily better accuracy.

As far as rifling goes, I believe the bullet weight determines the twist you should select. Different weight bullets perform better with different twists. Here is an article that discusses rifle twist.

Understanding twist rates on AR-15s | Xtreme | idahostatejournal.com
 
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I'd hold on to anything 16" or longer given the whole pistol brace / SBR fallacy currently underway.

All of those pistol length weapons may need a registered host under the NFA if stupidity persist.
 

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Twist - 1/8 is the best all round, straight plinking 1/7 is perfectly fine.


Stay away from 14.5" barrels.
 

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Twist - 1/8 is the best all round, straight plinking 1/7 is perfectly fine.


Stay away from 14.5" barrels.

Why is the entirety of the military M4 platform wrong in you estimation?
 

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That green tip isn't gonna be the most accurate out of most any barrel anyway, but I tend to favor 1:7 because I like shooting heavy pills and does well enough with 55gr plinking loads on steel. Some want a 20" to get more out of the round, but for an all purpose rifle, meaning something I'll carry in the field, 16" is as long as I personally care to go.
 

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If you want to be accurate to 500 yards then yes, a 1:8 twist to stabilize the 70, 80 grain bullets. 1:8 still fine for run of mil 55 grain at 200 yards.

Just fyi, those steel core green tip 62 grain bullets are fine for your plinking but not going to win a marksmanship contest
 
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Why is the entirety of the military M4 platform wrong in you estimation?
Civilians must permanently attach a muzzle device to extended the barrel to 16".

The military is not subject to the NFA.
 

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Civilians must permanently attach a muzzle device to extended the barrel to 16".

The military is not subject to the NFA.

So a legal issue not a performance issue. Ok.
 

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Why is the entirety of the military M4 platform wrong in you estimation?
I live in a very urban area, and the only time I'd ever shoot it is out at the family farm like twice a year at most. I'd like to be able to scope it and maybe shoot out to a few hundred, let's for the sake of conversation a critter gun out to 500.
What is the recommendation for length and twist to buy?
I have competed with military issue M16A2s and M4s out to 600 yards, most recently in March. They aren't even close to suitable for that range. There's a reason the military qualifies at 50 to 300 meters.
 

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For just straight up target shooting I'd go 20" however shooting out to 500 yards is hard if you haven't done it before so don't be disappointed if you suck at first. Twist rate will be either 1/7 or 1/8 because you are gonna need to stabilize heavier rounds to kill critters humanely at that range. Aero precision is a fine rifle so you are good on that front.

Your biggest expenditure will be an optic you are gonna need to spend some decent cash on good glass to humanely take critters at that range. I'd start researching optics and saving up for that next.
 

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Realistically a 16" bbl in 1/7 or 1/8 or even 1/9 twist is completely suitable for 200-300 yards ranges which is far outside the range of what most AR15 shooters shoot. A 16" bbl carbine is also the most versatile in terms of convenience, handling accessories etc. It's become kind of the standard America's Rifle.
 

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Well IMHO, IF YOU GET, HAVE THE LOWER,you should get the rifle together first. I would use the Aero "rifle" lower first. Put it together with the 16 inch upper you have, get it fully functional.
I am new to this sight but have been playing around with builds of sorts for years. Most every gun I own has either been built or had a major repair or mod, by me.
Most AR 15 lowers are sold none designated, unless built as something.
BUT......That Aero "Rifle" lower might be inventoried, or designated some where as a rifle lower. Maybe, Maybe not. But if it is, a pistol upper can never sit on it. At least with out a 200 buck tax stamp and a crap load of paper work plus limitations, making it a short barreled rifle. Hopefully it is not in a box with the pistol stuff.

Problem you have is that you have a bunch of rifle and pistol stuff and no gun yet.
Thing is ATF interpretation of laws are changing. Intent to build a short barreled rifle, can get you 5 to 10 now.
Hopefully you have your rifle stuff and pistol stuff separate.

Sounds like you have enough parts to build a rifle, so build that first and keep it together. Harder to claim intent to build a short barreled rifle with a fully assembled rifle. Then having your pistol parts ( short barreled uppers, pistol braces and such), all together in a box labeled pistol build stuff.

The lower and upper combo you have should make a fine rifle for hunting at 100 to 200 yard or so, or shooting steel with cheap store bought ammo. You can always put an arrow rifle upper on it later.
Plus you have to start somewhere.
 
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