Thread: AR15 Info

Any chance those that know - could we do up a bit of a ar15 info thread

Perhaps the basics of operation, interchangeability, calibers, things to consider/know - what to avoid etc, what would be a good starting point etc - not so much as brand x is the best etc - then a list of Brands available here

Good call FG


Sent from my iPhone using Tapatalk. So please forgive my sausage fingers!!!

One thing I have learnt reading around in here is dont buy one from guncity, or gunshitty as some people like to call them in that thread

I doubt anyone will agree on brands...

Yeah to both -

Just general beginner information - so people can make a informed decision -

Heres a thing I wrote a while back for Tussock about what to look for



-Fast twist barrel - With a 14.5" barrel you need to be able to shoot the ~77gr bullets for .223 to kill larger things well (Goats, etc). 1:7 is ideal and you can still shoot factory 55gr or whatever through it.

-Free floated handguard - The forend. Traditional M16A1/A2 and M4 style handguards aren't free floated, and you can end up with bad accuracy and varying point of aim depending on the pressure you put on the handguards while shooting.

-No fixed iron sights - The traditional triangular 'A2' front sight/gas block isn't desirable for a few reasons - usually they're on rifles without free floated handguards for a start. They're pinned to the barrel and it's a bitch to remove them to replace the handguard. They also end up in the sight picture of your optics. It's easy to get aftermarket irons to mount on your action rail/top handguard rail if you want them - you can get folding "backup irons" (known as BUIS) which are nice to have if you get decent ones. A low profile gas block under the handguards is better.

-Mil-spec/M16 bolt carrier - A proper milspec BCG has more steel at the rear of the bolt carrier than some non-milspec ones sold by lower end companies. Milspec is more reliable because of this extra weight and also correct dimensionally.

-MPI tested bolt *- Magnetic particle inspection tested. You want to buy from a manufacturer that does individual MPI testing of each bolt they make. Because of the complex shape of the AR15 bolt and the steels used small flaws in the steel can result in rapid failure of the bolt, inside a couple of hundred rounds. Individual MPI testing ensures that you don't get a bolt with these flaws. It's a quality control and failure prevention thing

-Properly staked gas key screws - The gas key is the part of the bolt that the gas pushes on to work the action. Staking is a method of securing screws so that they don't come loose. Gas key coming loose = bad

-General quality - If you buy from a lower end manufacturer you're more likely to end up with problems of things being out of spec dimensions, as well as lacking the above features. Pin holes in the lower being incorrect dimensions or in the wrong place, threads not straight, lower parts kit parts being out of spec, etc. Another problem with lower end manufacturers is that the picatinny rail on the upper receiver (or your handguards) tends to be out of spec which can cause accuracy problems and mounting problems with your optic. Lower end manufacturers of things like handguards tend to be heavier and weaker than better ones. More money = more quality control.

-Stay away from piston systems - The AR15 was designed as a direct impingement rifle, it works perfectly well as designed if you have quality parts etc. Piston systems are a stick-on bandaid for a problem that doesn't really exist, and they cause their own problems - carrier tilt leading to very rapid wear of the buffer tube, poor accuracy, etc. Especially any you're likely to see in NZ, as they'll all be lower end ones.

awesome Gimp, stuff like that is great

gimp's summary is good.

I can't really be arsed typing everything out in my own words, so I will rip useful info off various sights.

This is from Ask Foghorn: Gas System Length on the AR-15 | The Truth About Guns and gives a good overview on AR gas systems.

Carbine, mid length, rifle length. What do they mean? Can I run a carbine length on an 18″ barrel? A rifle length on a 16″?
What gives?

Well, you can do whatever you want, but that doesn’t mean the gun will run. Choosing the right gas system is a delicate balance between getting enough gas to cycle reliably and keeping your rifle from beating itself to death. So, which one is right for you? And what is it all about? . . .

Hiram Maxim figured it out first — there’s a TON of wasted energy when a gun goes off, energy in the form of recoil and noise. And if you could capture that energy, you could use it to do something useful like cycling the firearm automatically. Maxim’s design used the recoil of the firearm to reset the gun and load the next round, but it required a massive gun, and wasn’t exactly mobile.
The Vickers gun, with its “muzzle booster,” was one of the first designs to use the force of the expanding gasses rather than the force of the recoil to work the action of the firearm. Similar firearms, such as the M1 Garand and G41(M) would continue to use devices attached to the muzzle to redirect gasses to operate the action, leaving the barrel completely in tact. Browning took it one step further with the B.A.R. or Browning Automatic Rifle, which used a gas system that we would recognize today.

The standard modern gas system (illustrated here thanks to Wikipedia) uses a small hole in the barrel much before the muzzle to redirect some of the gasses to work the action. Bleeding off the gas before the bullet leaves the barrel means the gasses will be MUCH higher pressure than they would be at the muzzle, and allows the action to cycle faster.
There’s a slight issue with using a gas port, especially on the AR-15 platform: barrel length.

In order for there to be enough force to cycle the action, the bullet needs to still be in the barrel when the gas hits the bolt carrier, like a cork in the champagne bottle keeping the pressure up. This is also referred to as “dwell time,” the measure of how long the bullet is in the barrel.
And since the bullet is constantly moving, there needs to be a sufficient length of barrel left so that the bullet leaves the muzzle only after there has been enough gas transferred to the bolt carrier to make the whole thing work. Too much barrel and the bolt is “over gassed,” leaking all over the place making a mess and possibly damaging the system by applying too much force. Too little barrel and there isn’t enough force to unlock the bolt and fully cycle the action.

The original AR-15 came in one barrel length, 20 inches. But as we have shortened the barrel over the years the gas system has needed to be adjusted accordingly to keep the right balance between giving the gun enough gas to cycle the action reliably and keeping the gun from tearing itself apart, since too much rearward force can damage the buffer assembly and other components.
The trick is, as you shorten the barrel, you should move the gas port closer to the muzzle in order to decrease dwell time after the round has passed the gas port. For example, the difference in pressure 9 inches out and 7 inches out from the chamber is almost double, meaning the bullet should probably leave the barrel sooner with the 7 inch port. There are some exceptions to the rule, but for the “proper” gas length that’s the idea.
In order to make things slightly simpler for us consumers, manufacturers have standardized the length of gas systems and provide a guide for which system goes on which length barrel.

Here’s ye olde chart:
System Barrel Length Port Distance
Pistol < 10 inches 4 inches
Carbine 10-18 inches 7 inches
Mid 14-20 inches 9 inches
Rifle 20+ inches 12 inches

You can see that the distance between the port and the minimum barrel length increases as you go up the chart – carbine is 3 inches, mid is 5 inches, and rifle is 8 inches. Which keeps things under control.
The problem is with the carbine length gas system. People love to have their stuff “mil spec,” and since the military spec is a 12 to 14 inch barrel a carbine gas system is what they use. Unfortunately, with that whole National Firearms Act thing, civilians generally are restricted to 16 inch barrels. Using a carbine gas system on a 16 inch barrel will work (and work remarkably reliably), but you run the risk of having your rifle wear out quicker. It also leads to some nasty backpressure when using a silencer, which tends to leak out the back of the receiver and straight up your nose. Ask me how I know.
The main exception to the rule is weird calibers. With 5.56x45mm NATO the chart is perfect, but when you have things like .300 AAC Blackout that have different pressures and such it gets complicated. 300BLK is recommended to have a carbine length system for anything 16+ inches and a pistol length system for anything under 16 due to the powder being used, but in general you should listen to the manufacturer’s recommendation for what system to use.

I will add:

Using a suppressor without an adjustable gas block will result in a lot of excess back pressure, even in a rifle with a proper barrel length to gas tube length ratio. This will foul up the system much faster than usual and will induce more stress on your bolt. If you use on on your AR, get an adjustable block. A heavy buffer will help tame the cyclic rate and prevent bolt bounce, but most A cat Ar's are running rifle buffers which should be sufficient.

Buffer comparisons from Vuurwapen blog



You can see how different buffers effect the behavior of the action during cycling

My observations from using different AR's:

A two point quick adjust sling is really the most sensible way to carry an AR in the field. Your shoulders take the weight of the rifle, you can cinch it close to your body while scrub bashing and at the pull of a tab your rifle is free for you to fire. My favorite is the Viking Tactics padded sling. The Blue Force Gear Vickers combat application sling is lauded by many as the best, but I have one and don't get the hype. You can get the same dumbed down sling from Redimag for like $USD20. Avoid single and 3 point slings.

Forward grips are great for shooting in a range environment but tend to bang into your legs when you are out hunting and slinging your rifle.

Front sight posts are a pain in the arse with scopes on a sunny day. If it catches the light your scope will "white out".

Don't bother cleaning it. Forget all AR vs AK bullshit. You're not in Afghanistan. Just bung lube in the BCG and it should run. I use diesel engine oil because it doesn't evaporate and has detergents which break down carbon.

Rapping a piece of electric tape around the bottom of metal mags will stop them from rattling in the mag well when you're hunting.

Rubbing Chassis grease on the recoil spring will eliminate the "boing" sound every time you fire the rifle.

I'll add more as they come to mind.

Here's my tip:

"Don't buy cheap nasty airsoft quality junk"


Including accessories.

I bought an airsoft AFG cuz I didn't know if I would like it. Still undecided. But the part itself is solid. My mate is running an airsoft CTR stock on a lower and it is going ok. Who cares if it breaks. It's only 20 bucks. Stay away from airshit rails, sling mounts and stuff like that

my tip would be Decide what rifle you want to end up with, Pick each part write it down or go on AR builder.com then order that, not buy a basic one and spent your next 6 months wages on little bits and pieces.

Im going to stick my neck out and say what makes a ar15 accurate is the barrel and trigger. barrel must be of good quality and be free floated. trigger must be easy to use. good mounts and good glass come next.

BCG - bolt carrier group. this is the bolt of the rifle

Free float tube - this is the fore grip of the rifle by free floating it dosent contact the barrel aiding accuracy

lower - the bottom bit that holds the trigger, stock, and magizine well.

upper - the top bit that has the barrel, fore-end, sights, gas tube and houses the charging handle and BCG



If you suppress your AR15 and start getting debris and gas blown into your eyes do this - Do It Yourself Gas Busting Charging Handle [2009-09-29] - 03DESIGNGROUP

I disagree about the cleaning comments above, barrels must be looked after as much as any other rifle. inside and out. chrome lined I have no experiance with.
get a crome lined BCG if it is offered they are great.
the rest of the rifle is basically Ali. bar the pins trigger and springs ect.
Go light on any oil you spray into the action area as it can cause extra burning of eyes

A couple things I have found (that haven't already been mentioned) with my very limited AR experience. Most of the US stuff relates to military or home defense situations (or zombie shooting) and isn't required for hunting applications. Like backup open sights (I cannot understand why so many americans like the A2 style front post sight?) Not required - not life and death when hunting

I also tired QD sling mounts - found my sling was always twisted the wrong way round and why do I need to take it off quickly anyway? You do need to have the sling mounted on the side so it carries better

Quick Release Scope mounts - Just another failure point, and when I had them on I always had a doubt in my head that they might be moving slightly - I do like the one piece bases though

The triggers are no way near any hunting rifles and so if you are used to a clean crisp trigger pull you will need a timney AR trigger or similar

The other thing is - AR's are generally very short and therefore VERY loud - especially with a brake - I got a suppressor put on pretty quickly

otherwise I agree with Gimp and Beavis and everyone else

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