AR15 Discussions FAQs 1) AR15 FAQ and buying advice (by juslearnin)
- READ THIS FIRST if you're new to AR15. It also has a lot of info even if you already know more than the basics. There is also a left-handed AR FAQ available (by Evile)
once you familiarize yourself with the primary FAQ and have questions about left-hand specific configurations.2) MOLON's Collected Posts
- Arfcom user Molon
has published lots of very informative articles about the AR15, many of them about shooting groups, sighting in, ammunition reviews, as well as the aforementioned discussion about the differences between .223 and 5.56. This link should be considered a MUST-READ.
Relevant sections include:
3) Acronyms and abbreviations used on AR15.com4) AR15 Ammo FAQ
- Sighting in and shooting for accuracy
- Optics-specific evaluations and reports
- Miscellaneous technical information
- Accuracy evaluations of various rifles
- Ammunition reviews
- Information about all things ammo related, including terminal ballistics, steel case ammo, and barrel twist rates.
5) Is .223 the same as 5.56, can I shoot .223 in a 5.56 chamber or vice versa?
In short .223 is not the same as 5.56 in chambering - though the ammo dimensionally is identical. Yes you can shoot .223 in 5.56, no you should not shoot 5.56 in .223. For details and explanations please refer to MOLON's archives above. 6) What Range to I zero my rifle for? How do I zero?
7) Miscellaneous FAQs
8) What is the difference between the Mil-Spec and the Commercial Receiver Extensions ('buffer tube')? Who uses what?
The commercial tubes are slightly larger in diameter where the stock slides, but slightly smaller in diameter when it screws into the receiver. Either can be installed on standard lowers, with the Mil-Spec one actually having the stronger interface (more surface area of the threads engage the receiver).
Mil-Spec ( 1.148" outer diameter): Colt, LMT, CMT (Stag, S&W, CMMG), VLTOR 9) I hear a 'SPROING' kind of noise when I shoot my AR - is something wrong? How do I get rid of it?
Commercial (1.168" outer diameter): Everyone Else (Bushmaster, RRA, DPMS, Olympic, etc.)
Another way to tell is a commercial tube is the same outside diameter as the points on the threads. A milspec size tube is smaller in diameter than the points on the threads so you can see where the threads taper down in size.
The noise is perfectly normal. It indicates the weapon is functioning and you'll be able to tell when it's time to change magazines by the change in sound. Of course if you're shooting under stress you won't notice it at all. 10) I want to work on my AR (change stock, fix something, replace barrel etc). Where can I find out how?
To get rid of the sound try using earplug instead of ear muffs. The hard case of the ear-muffs seems to transmit the sound better. Also, some have suggested using grease on the spring to dampen the sound, proper lubrication with CLP works as well.
11) I was 'hand cycling' some ammo and I noticed my primers were dimpled - is this a problem?
First think you need to do is download the '-23&P' Unit & Direct Support Maintenance Manual. You can download it in .PDF format it from this site: Unit & Direct Support Maintenance
Then you need to head to the Build It Yourself
forum and read the tacked threads for tips & tricks on how to do things. The forum even covers free float tubes, which the -23 does not.
I notice a round I ejected from the chamber had a dimpled primer - OMG is this a potential slam-fire !?
Relax, that is perfectly normal for a rifle that does not have a spring loaded firing pin. This sort of issue can also be see on other rifles with a floating firing pin 13) What are 'M4 Feedramps' and how do I know if I have them?
14) I'm interested in an AR in a caliber OTHER than .223/5.56 where can I find out more?
They are the feed ramps introduced with the M4 carbine that improved feeding with the M855 round - especially when the magazines were dirty/worn. Unlike previous ARs, these ramps continue onto the upper receiver - Click here to see the images
(images courtesy of Randall from AR15Barrels.com)
For other calibers we have specific areas of this site setup. Many popular calibers even have FAQs tacked up in the top of these forums.
15) How many calibers can I get uppers that fit my .223 (AR-15) lower? What are they?
- If you are interested in .22 LR or Pistol Caliber uppers (.22LR, 9mm, .40, .45 etc) visit the Rimfire and Pistol Caliber Forum
- If you are interested in other intermediate & wildcat calibers (5.45x39, 6.8 SPC, 6.5 Grendel, .300 Whisper, 7.62x39, .458 SOCOM, .50 Beawulf etc) then visit the AR Variants Forum and check out the FAQs there
- For Armalite (brand) AR-10s (tm) visit the Armalite AR-10 Forum for all other brands (DPMS, RRA, Knights) of .308 / 7.62x51 NATO AR rifles visit the AR Variants Forum
While the list is nearly endless with all the wildcats possible. Here are the some of the more common and more interesting uppers that are (or have been) produced for the standard AR-15 lower (may not be up-to-date):
- 6 x 45
- 7 x 40
- 357 Mag Rimless
- 300 Whisper / .300Fireball / 300-.221
- 6.5 x 40
- .30 Coyote (30 x 45)
- .17 Remington
- .17 Mach IV
- .20 Tactical
- .19 Calhoun
- 5.7 FN (developed by Rhinland Arms - no word yet on who is going to mfg it)
- .204 Ruger
- 6.8 SPC
- 30 HRT
- 338 Spectre
- 10 mm Mag
- 219 WASP-C
- 7.62 x 40
- 7.62 x 39
- .338 x 39
- 6 PPC
- 6.5 Grendel / 6.5 AR / 6.5 PPC Improved
- 22 PPC
- 7 sCAR ....
- 30 Carbine
- 5.45x39 / .21 Ghengis
- 7 BR
- 6.5 BR
- 300 Sabre
- 8mm (belt fed upper)
- .308 (again a belt fed upper - no longer available)
- 458 SOCOM
- 44 Mag
- 440 CorBon
- 44 AMP
- .475 Tremor
- 50 Beowulf
- .50 BMG (single shot)
- .50 Blackpowder (1 made)
- 22 LR
- 17 HV
- 224 BoZ
- .357 Sig
- .357 Auto
- 223 WSSM
- 243 WSSM
- 300 WSSM
- .30 RAR
Many thanks to Marty at Teppu-Jitsu for starting this list.