What is the difference between a heavy and light 16inch barrel, and for a M-4 which one should I get.  A light weight or heavy barrel?  And finally is 1x9 good or pay more for a 1x7.  And do i need chrome lined with I do not use corrosive ammo?  Thanks in advance.

Scott

What use? Defense, hunting, plinking, target shooting or safe queen?

The difference between the barrels is weight. A heavy barrel has a larger OD so it weighs more. It also takes more to heat it up so your riffle stays more on target longer when firing repeatedly. It actually dosen't take that much to heat up either barrel. A heavy barrel, also is stiffer so it would make the riffle accurate under more various loads. You can always tune a barrel for resonance, but the heavier the barrel the less it will resonate (hence the bull barrel also being more accurate). Anyway, you can also get the barrels in fluted which splits the difference more or less. A fluted heavy barrel will be lighter then a heavy barrel but heavier than a light barrel, it will also resonate more than a heavy barrel but less than a light barrel.

If your riffle is going to be a bench shooter, then by all means a bull barrel is the way to go. If you're going to be carrying it a fair bit a heavy or light will make life alot easier. If you think you may rapid fire, even if occasionally I'd go for the heavy barrel.

Now the twist rate. The 1 in 9 is good for most ammo. If you'll going varmenting and want the 45 grain stuff then that's the way to go. It'll work well with 55 grain ammo which is the most common, and even 65 grain green tip mil-surp, but it won't do as well with the heavy, rounds, tracer, 77 grain and up. Well it will but not reliably enough. Also with the 1:9 twist your barrel should last a little longer and you ought to have a little higher velocity.

The 1 in 7 is a fast twist. Fast enough that it can actually compromise accuracy with the light varmint ammo. Fast enough that in some cases it can cause the ammo to come apart in flight. On the other hand it will definatley do a good job with tracer and heavy ball, which is itended for longer range effectiveness primarily.

I'm not as sure about chrome lined... my understanding is that chromed barrels are more durable but not as accurate. Personally I'm going to be looking at a stainless barrel for my project AR.

Everyone has a opinion and here is mine. The heavy under the CAR length handguard barrels are very stiff and usually more accurate than most users. They are also easy too find new, and are a little easier to find slightly used. They are going to generally cost you less also. I have compared my heavy under the handguards barrel from Armalite to a light under the handguards ADCO turndown that a friend owns and according to my scale his is about 8oz lighter than mine.
The 20" govt profile Colt barrel that I have on another rifle is a full 1 pound 16oz lighter than the same length heavy under the handguard barrel.

Quoted: What use? Defense, hunting, plinking, target shooting or safe queen?

+1 - Without knowing your intended usage it's hard to tell you what way to go?

Common misconception - A heavy barrel profile will not make a barrel any more accurate then a thin profile. What it will do is keep the barrel from heating up as quickly as a thin barrel. As a barrel heats up, your groups will open up proportionally. HBAR's are typically cheaper because they involve less work for the manufacturer. My opinion - AR's are supposed to be light, handy weapons and an HBAR goes completely against from that. They make the AR's too front heavy and unbalanced. If this is going to be a bench only or varmint rig, where the utmost accuracy is priority #1 then fine go HBAR. Otherwise  a light weight AR barrel, even when hot is more then accurate enough for it's intended purpose. A medium profile is a nice compromise but they are not very common.

For me, go chrome or go home. The only down side to chrome is it's reported effect on accuracy. That said, I bet there's not even 5 guys on this whole site that can out-shoot a chrome lined barrel. For around $50 more, a chrome lined barrel is more resistant to the elements, will be easier to clean and may be more reliable as cases are less likely to stick in the chamber. It's a no brainier as far as I'm concerned.

1/9 vs 1/7? Easy, what do you plan to shoot? (The "Ammo Oracle" is your friend here). My readers digest version of an opinion - 1/9 is fine for 98% of the people out there. If you happen to fall into the 2% that will be shooting the heavier defensive rounds (~75gr and up) or just want to be as close to "Military Spec" as possible, then get a 1/7

Ok this is going to be a tactical weapon for practicing before I deploy and doing tactical shooting courses. I am looking at a M-4 type weapon for tactical reasons.

Scott

Quoted: Ok this is going to be a tactical weapon for practicing before I deploy and doing tactical shooting courses. I am looking at a M-4 type weapon for tactical reasons. Scott

Well then you definitely want something light under the handguards and chrome lined as that will be what you use when you deploy. I assume for practice you will be mostly using 55gr ammo so either 1/9 or 1/7 will be fine.

I haven't been keeping that close on eye on them lately but a few months ago, the best deal in quality M4 types uppers with the correct profile and chrome lining was the Stag upper sold by a number of dealers on the EE. Good luck and kept safe over there

HER'S WHAT I FOUND;had the 20' hbar, and it shot  extremely tight groups off the bench, but I never carried it much....bought a bushmaster superlite 16 inch, man, what a difference! I just can't put it down, it's exactly what i wanted...first five shots at 100 yards in 98 degree weather, the holes are satisfyingly close....then, it will start stringing low and to the right.but what am i gonna shoot at 100 yards that needs more than five shots anyway!I love the superlight....

Superlight or M4 sounds about right for your application.

FYI: I've found that a free float tube really improves accuracy with a Superlight weight barrel profile.  I made a National Match style float tube that allows regular CAR hand guards to be mounted over the float tube.  

If you build up a nice upper with float tube and a small bipod (Click this link you won't be sorry) can you take it with you when you deploy?  All you would need is to exchange the AR15 bolt carrier for an M16 bolt carrier and use uncle sams lower

No I cannot take it when I deploy.  I will get a M-4 when I leave home station or pick one up when I get in country.  I will look into the free float tube.  Thanks for teh help

Scott

I will be on my way out of the big sand box soon. will this be your first deployment and what MOS are you coming here as?
Der

This will be my first time to the box for a deployment.  I have been to Dubai but that was a 7 week vacation.  Stayed in a hotel the whole time

I am a 21R3 Logistics Officer USAF Jr. Captain

Hey, I'm an Army Major in a Movement Control slot.  I'll be seeing you at the ADACG, buddy!