Question about used ARs.

[user]

I am new to ARs (and guns in general TBH).

With regards to a used AR, which parts are affected?

If one were to replace the "lower", would that in essence give me a new rifle?

[Armor Snail]

Yes. The lower reciever is the transferable "gun". The rest is just parts.

[M&P Chris]

There are 2 halves to an AR. A upper and a lower.
Replacing a lower will give you half a new gun. New will be trigger group, receiver, buffer and tube. And things such as bolt release and mag release.

I would look at the bolt carrier group that is in the upper. I would take notice mostly of the upper when looking at a used AR. JMO

[M&P Chris]

Yes. The lower reciever is the transferable "gun". The rest is just parts.

Good point armor snail. Also this the lower receiver is considered the firearm.

[Splittiebus66]

Typically the Lowers/ Lower parts are pretty bullet proof and last a real long time. If you are looking for enhanced reliability ,along the lines of a new rifle, out of a used AR ...M and P Chris is correct. The Bolt/Bolt carrier group contains the parts that typically wear first. Mainly the extractor/ejector springs or extractor assembly, followed by the bolt itself. These would be what you'd want to replace 1st. You could just buy a new bolt and rebuild the old one if you want an extra. The action spring should be looked at and replaced if the round count is around 3 to 5K ( chrome silicon springs like the Sprinco last longer IIRC) , along with the barrel of course, if the round count is real high( most barrels are rated from 10000 to 20000 rounds depending on type and steel used ).

[TerryK]

I don't think a person would replace a lower ever. The upper has the wear parts like the bolt carrier assembly and barrel. For the most part, the lower itself will never wear out, of course the trigger parts will show wear, but they can be replaced in minutes at minimal cost. A used lower in excellent condition will last a lifetime or two.

[user]

So if anything, its the "upper" that I would consider replacing, correct?

Typically the Lowers/ Lower parts are pretty bullet proof and last a real long time. If you are looking for enhanced reliability ,along the lines of a new rifle, out of a used AR ...M and P Chris is correct. The Bolt/Bolt carrier group contains the parts that typically wear first. Mainly the extractor/ejector springs or extractor assembly, followed by the bolt itself. These would be what you'd want to replace 1st. You could just buy a new bolt and rebuild the old one if you want an extra. The action spring should be looked at and replaced if the round count is around 3 to 5K ( chrome silicon springs like the Sprinco last longer IIRC) , along with the barrel of course, if the round count is real high( most barrels are rated from 10000 to 20000 rounds depending on type and steel used ).

10,000? Woah. The ARs I'm considering have been fired 100 to 400 times (so I'm being told).

I don't think a person would replace a lower ever. The upper has the wear parts like the bolt carrier assembly and barrel. For the most part, the lower itself will never wear out, of course the trigger parts will show wear, but they can be replaced in minutes at minimal cost. A used lower in excellent condition will last a lifetime or two.

Good to know.

[Noah_Zark]

I don't think a person would replace a lower ever. The upper has the wear parts like the bolt carrier assembly and barrel. For the most part, the lower itself will never wear out, of course the trigger parts will show wear, but they can be replaced in minutes at minimal cost. A used lower in excellent condition will last a lifetime or two.

^^^ THIS.

Terry nailed it. The major wear parts are springs, barrel, bolt & its parts, bolt carrier, trigger group. Speaking as a former Marine armorer with 100s if not 1000s of M16A1s across the bench, one would replace an AR extractor and spring, firing pin, barrel, bolt, carrier key, buffer spring, upper receiver, and FCG springs. Replace those parts at the end of their service lives, and you have a "new" AR.

The upper receiver sometimes cracks just behind the threads if the weapon is subjected to rough handling in a combat environment.

Similarly, the threaded boss for the buffer tube on the lower receiver sometimes cracks if the weapon is handled roughly and dropped.

The average civilian won't have to worry unless they drop it from a two- or three-story roof, and just right.

Noah

[Gun]

If one were to replace the "lower", would that in essence give me a new rifle?

No. You would have to buy a new rifle, to have a new rifle. You can refurbish a used rifle.

You stated that the rifles you looked at had low round counts. Hardly any wear, unless the previous owner over zealously cleaned the barrel.

You didn't mention manufacturer. Problem is that most high production ARs are over gassed, done so the end user can shoot cheap Russian ammo. Shoot the good stuff, the moving parts could work more violently, precipitating wear on those parts.

Problem now, just getting an AR, at a reasonable price, hopefully one that functions properly. There are stickies at m4carbine.net that talk about this. Use the search function for particular questions as they have all been discussed. Here is one link;

http://www.m4carbine.net/showthread.php?t=45372

[user]

So, if I were to buy a "complete" upper and a "complete" lower, would that result in a whole, finished rifle?