Hi Folks,

I am new to this forum and AR15.....I am also new to the world of AR's in general, but I learn fast.

I have been looking to obtain a .243 rifle for a while and have recently decided I want to build, what I have since learned, is referred to as an "AR Variant" in .243.

I am a machinist by trade and I have a gunsmith background (CST 1996). I have built 2 custom bolt guns, and one lever gun.
I understand the concept of building a rifle, safety factors, etc.

What I am trying to determine is, which parts are caliber specific, such as the bolt and the barrel, and are the parts readily available?

Thanks

I have a new in box .243 Armalite A4 upper for sale for $500. Stainless barrel. No B,C,CH.
[email protected]

pretty much all the .308 parts will be just fine in a .243, since it's based on the .308 case

john

What he said

Only difference tween a .30cal AR10 and a .243cal AR10 is the barrel chamber/bore

Thanks for the Feed back,

So it appears I should be researching the AR 10 rather than the AR15. After looking through a lowers parts list on Armalites, AR10 vs. the AR15 I found most parts are interchangeable. I am confused about the non-interchangeable parts though.

The buffer and buffer spring are among the non-interchangeable parts, which makes sense considering the .308 is a bigger cartridge. However that begs the question, of why it is possible to mount an upper chambered in WSSM (.223, .243 and .25)(Olympic Arms) on a standard unaltered, mil spec AR15 lower, which would include a .223 buffer and buffer spring.  

So then why is it necessary for Armalite to require a different buffer and buffer spring for the AR10 in .308, is this just an Armalite thing, or I am I missing something?

Very few parts are interchangable between the AR-10 and AR-15 as the AR-10 is significantly larger than the AR-15.  The pistol grip and stock are about all that can be interchanged ..


The WSSM uppers you mention are made by Olympic Arms and were designed to work with those rounds specifically.  While the uppers will mount to standard lowers and can use standard hand gaurds, the uppers are not interchangable with either mil-spec AR-15 uppers or AR-10 uppers.  They are a beast upon themselves with custom upper receivers, custom bolts and carriers, custom barrel extensions and custom magazines (altered 223 mags that will not work in 223 service anymore)