Noob AR Question

DirtyHarold · September 28, 2020, 10:58 AM

Is any AR upper compatible with any AR barrel/gas block/hand guard combo? Assuming it is all mil spec?

Thinking about getting a completed upper but I want to be able to install a different barrel and handguard etc.

Is there any reason this won’t work?

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CarJunkieLS1 · September 28, 2020, 01:56 PM

For handguard be aware that 99% of handguards you'll find will require a different barrel nut. The handguards will come with that barrel nut though. Gas tube length is a consideration and so is gas block inner diameter. There are .625, .750,.875, and .960 gas blocks or something like that.

As long as your handguard comes with the barrel nut, the gas system is the same, and gas block diameter is the same then it will all for together no problem. Oh and if you plan to cover the gas block with the handguard make sure the gas block is the "low profile" type.

Kreyzhorse · September 28, 2020, 04:27 PM

Why would you buy a completed upper if you want to install a different barrel and hand guard?

Any AR mil spec upper will use any other mil spec parts. Gas tube and blocks vary based set up.

Metal god · September 28, 2020, 04:54 PM

Quote:

Originally Posted by OP

Is any AR upper compatible with any AR barrel/gas block/hand guard combo? Assuming it is all mil spec?

Short answer no , long answer definitely not . No wait you said assuming it's mil-spec , in that case generally yes . In that case you will end up with a GI M16/M4 style/look firearm period cus that's mil-spec . No gas block because that's part of the front sight base . You can get different handguards that will fit mil-spec rifles . Magpul seems the most popular .

I would say one thing to look out for is the wording and when they apply it . Just because mil-spec is in the sentence doesn't mean the whole thing is mil-spec . You see this a lot with barrels , you'll see mil-spec in the definition but the only thing actually mil-spec is the type of metal used and the finish . They leave out that the barrel is not chrome lined or magnetic particle inspected (MPI) High pressure tested (HPT) so watch out for the wording per mil-spec and how it applies to the product .

I don't think you're asking the right question because if you go away from mil-spec you can have a much better firearm . Which in that case no not all the parts will fit with each other . All the barrels will fit in the upper or they should but the type of barrel nut will dictate your handguard or rail . As stated above then you get into gas blocks , front sight base , gas tubes etc . If you're new it can seem overwhelming but understanding the fundamentals of the AR operation and function goes a long way to putting one together .

I know a lot about them but I'm not the best at explaining things about them except general knowledge . There are others that will come along that will be much better help

kymasabe · September 30, 2020, 05:00 AM

If you're going to strip a complete upper apart and replace the barrel, nut, gas block, gas tube, and handguard, you might as well skip all that disassembly and just buy a stripped upper receiver too and assemble a new upper instead. I've built dozens of uppers on Anderson receivers (many on the slick side upper, with no forward assist or dust cover) and never had an fit or finish problem with them, and they're affordable and available. If Anderson doesnt thrill you, there's always Aero, Ballistic Advantage, Spikes Tactical, etc...
I usually buy mine here:
https://www.righttobear.com/anderson...-p/m4slick.htm

Metal god · September 30, 2020, 12:04 PM

Yep , I think the OP has his narrow question answered . He now needs to come back and elaborate more specifics.

September 28, 2020, 10:58 AM	#1
DirtyHarold Senior Member Join Date: July 23, 2015 Posts: 158	Noob AR Question Is any AR upper compatible with any AR barrel/gas block/hand guard combo? Assuming it is all mil spec? Thinking about getting a completed upper but I want to be able to install a different barrel and handguard etc. Is there any reason this won’t work? Sent from my iPhone using Tapatalk

September 28, 2020, 04:27 PM	#3
Kreyzhorse Senior Member Join Date: April 12, 2006 Location: NKY Posts: 12,463	Why would you buy a completed upper if you want to install a different barrel and hand guard? Any AR mil spec upper will use any other mil spec parts. Gas tube and blocks vary based set up. __________________ "He who laughs last, laughs dead." Homer Simpson

September 30, 2020, 05:00 AM	#5
kymasabe Senior Member Join Date: June 10, 2005 Location: SW Florida Posts: 2,747	If you're going to strip a complete upper apart and replace the barrel, nut, gas block, gas tube, and handguard, you might as well skip all that disassembly and just buy a stripped upper receiver too and assemble a new upper instead. I've built dozens of uppers on Anderson receivers (many on the slick side upper, with no forward assist or dust cover) and never had an fit or finish problem with them, and they're affordable and available. If Anderson doesnt thrill you, there's always Aero, Ballistic Advantage, Spikes Tactical, etc... I usually buy mine here: https://www.righttobear.com/anderson...-p/m4slick.htm __________________ God's creatures big and small, eat them one, eat them all. Last edited by kymasabe; September 30, 2020 at 05:05 AM.

September 30, 2020, 12:04 PM	#6
Metal god Senior Member Join Date: April 10, 2012 Location: San Diego CA Posts: 6,876	Yep , I think the OP has his narrow question answered . He now needs to come back and elaborate more specifics. __________________ If Jesus had a gun , he'd probably still be alive ! I almost always write my posts regardless of content in a jovial manor and intent . If that's not how you took it , please try again .

September 28, 2020, 01:56 PM	#2
CarJunkieLS1 Senior Member Join Date: October 1, 2013 Posts: 686	For handguard be aware that 99% of handguards you'll find will require a different barrel nut. The handguards will come with that barrel nut though. Gas tube length is a consideration and so is gas block inner diameter. There are .625, .750,.875, and .960 gas blocks or something like that. As long as your handguard comes with the barrel nut, the gas system is the same, and gas block diameter is the same then it will all for together no problem. Oh and if you plan to cover the gas block with the handguard make sure the gas block is the "low profile" type.