80% ar15 Quick Question

[kcstott]

Thanks KC for clarity...

Well there is a lot of confusion on the subject. It's just the same as a .45-70 load. you can only buy and use the trapdoor loads in all rifles. But buy the Ruger loads and you can blow up a old gun with it.

To me .223 and 5.56 is one and the same when you compare how the are measured pressure wise. Granted the long throat can produce a pressure difference like trying to shoot wheatherby mags in a non free bored chamber

[acj415]

the 762x39 is a caliber conversion for a standard ar-15 so you mill your blank to ar-15 specifications

So basically I buy a 7.62x39 upper and a pretty much any lower kit?

[Centaine]

There is no dimensional differences between the lowers for a 5.56 and one that is 7.62x39..... Again.... There is no difference in the lowers, they are the SAME. that means you would mill them to the same specs and use a standard lower parts kit for either or. Its the bolt, barrel and mags that are unique to 7.62x39.

[bohoki]

So basically I buy a 7.62x39 upper and a pretty much any lower kit?

yes and the proper magazine

[Eagle Eyes]

Yes and no


You can use a AR-15 lower made for 5.56 NATO for 7.62 x 39

BUT

You have to make sure the upper is a AR-15 not AR-10 upper as some manufacturers feel the 7.62 x 39 is to strong for prolong useage on a standard AR-15 design.

[wpage]

Its the crazy esoteric internet world of what works...

And what is fantacy. 223 yes 7.62 no. In the ar 15 platform.

Then there is plastic, aluminum, steel, etc...

[acj415]

Well I have a 80% polymer lower on the way...so most likely I will stick to 5.56. I wanted to make 7.62x39 because ammo is cheaper. I doubt that the lower would work for that now. Unless someone else has already done this.

[bohoki]

Well I have a 80% polymer lower on the way...so most likely I will stick to 5.56. I wanted to make 7.62x39 because ammo is cheaper. I doubt that the lower would work for that now. Unless someone else has already done this.

polymers barely survive 223 uppers

let us know how it turns out after a couple hundred rounds

[Centaine]

If you want cheap ammo, get a .22lr upper/conversion. I wouldnt even bother building one of those polymer lowers with a rifle cartridge, as they are known to break/fail under the adverse conditions of rifle calibers.