Noob question... interchangeability?

[Cyclemut]

So, I'm thinking of building my own, doing a lot of looking around.

One question that I can't seem to find the answer to is the interchange-ability of all of the parts.

Here's what I'm thinking. I'd like to get myself an 80% lower and finish it myself. Needless to say, no records and I can finish the milling myself.

But what parts can I put on what lowers, which uppers, barrels, etc.? If I were to get any lower, can I swap out bare lowers and put the firing control out of a cheaper lower into a better lower or is it all proprietary to their own stuff?

Signed,

AR-15less in Denver.

 

[RacerXXL]

So, I'm thinking of building my own, doing a lot of looking around.

One question that I can't seem to find the answer to is the interchange-ability of all of the parts.

Here's what I'm thinking. I'd like to get myself an 80% lower and finish it myself. Needless to say, no records and I can finish the milling myself.

But what parts can I put on what lowers, which uppers, barrels, etc.? If I were to get any lower, can I swap out bare lowers and put the firing control out of a cheaper lower into a better lower or is it all proprietary to their own stuff?

Signed,

AR-15less in Denver.

The M16/AR15 family of weapons is probably the most modular weapons system on the face of the planet. Correctly machined in spec uppers and lowers are going to be 100% interchangeable. There are machining tolerances like there are with any parts so some uppers/lowers will have a tighter fit then another given combination but as a rule they will fit. That's one of the beauties of the system. You want to have a carbine for tactical rile matches? No problem. Need to kill some coyotes and want say a 20" precision upper? No problem just remove the carbine upper, slap a complete 20" precision upper and voila you have a precision rig in less then 15 seconds. I know guys who have 4 uppers and 1 lower. All my upper and lowers interchange.

Same is true for switching a bolt carrier from one upper to another the bolt usually can be changed from one barrel to another but really should be checked for proper head space before use though. 5.56x45 mil-spec rounds are generating nearly 65,000 psi in the chamber.....not something you want to mess about with by introducing a bolt with incorrect head space. Any barrel built for an AR 15 will bolt onto any AR 15 upper with the exception of some of the QD barrel sytems.

For the lower any in spec lower parts will fit in any in spec lower. You have to be somewhat careful where you get your lower parts from, and all the parts really, as there are some poor quality control parts out there.

I ramble so let me summarize a Colt lower will fit with a Bravo Company upper using a Noveske barrel with a Bushmaster lower part kit and using a LMT bolt carrier and bolt with an Armalite stock. They are all basically built to the same spec.......it's just a matter of there quality control procedures and the materials they wish to use that make one better then the other so almost all parts interchange.

 

[RacerXXL]

Also have you found a place for the 80% lower yet? Sometimes they can be hard to find.

Also I have never had an extra upper that was not complete. I build an upper and the bolt carrier group (BCG) which is the bolt carrier, bolt, bolt cam pin, and extractor always stay with that upper/barrel. There is a gas tube fitment issue that can be a pain in the *** and make the upper unreliable if you have 4 upper and one BCG.

On the lowers the only part that can be easily removed once assembled is the fire control group (FCG), the trigger, and all the other parts are just a pain to remove but they are all fairly cheap.

 

[Cyclemut]

I found CNCguns.com and you can order the lower, although it depends on his stock or if he has enough pre-orders to get him to build them.

He has CNC'd an upper and offers files for the complete gun. Looking through a lot of stuff, they're a bit out of date. I'd get an upper, I don't think that would be an issue, I just don't want to have anything shipped to an FFL any more. Around here, they're jacking their prices for receiving something they don't sell so that they can still make a killing. What the hell is one to do? And it's surely not worth it to get your FFL just for a couple of weapons a year.

 

[RacerXXL]

I found CNCguns.com and you can order the lower, although it depends on his stock or if he has enough pre-orders to get him to build them.

He has CNC'd an upper and offers files for the complete gun. Looking through a lot of stuff, they're a bit out of date. I'd get an upper, I don't think that would be an issue, I just don't want to have anything shipped to an FFL any more. Around here, they're jacking their prices for receiving something they don't sell so that they can still make a killing. What the hell is one to do? And it's surely not worth it to get your FFL just for a couple of weapons a year.

The guy who owns and runs CNCguns is a member of a site I belong to and has a very good reputation, so you should be good to go there.

Yeah the FFL's have gotten out of hand with the transfer fees. They keep jacking the price up to try and counter folks wanting to purchase from online sources. What they don't realize is they alienate any potential customers by offending them with outrageous transfer fees. I'm lucky enough that my boss, the team manager, is a gunsmith in his spare time and an 07-FFL, manufacturer, and he does our transfers for free.

Machining on the upper is a little more critical to an accurate rifle and since it doesn't have to go through an FFL I would just get a completed one.