AR Build Question

[staten42]

My apologies first off for asking such a noob question, but:

Is it possible to build and a lower that is interchangeable with uppers of different calibers? (Ex: 5.56, .458, 6.8) If so, what components are needed?

 

[ZbornacSVT]

My apologies first off for asking such a noob question, but:

Is it possible to build and a lower that is interchangeable with uppers of different calibers? (Ex: 5.56, .458, 6.8) If so, what components are needed?

Very much so. Everything you listed can be run on the same lower without modification.

 

[loony1]

Very much so. Everything you listed can be run on the same lower without modification.

i would replace buffer and buffer spring if using a 6.8 or a .458 JMO

 

[BloodEclipse]

Very much so. Everything you listed can be run on the same lower without modification.

Your uppers must include the BCG for each caliber as well.

 

[451_Detonics]

Your uppers must include the BCG for each caliber as well.

Not for all calibers...for example the 300 Whisper uses the same BCG and magazines, there are a couple other calibers that also use the same.

 

[BloodEclipse]

Not for all calibers...for example the 300 Whisper uses the same BCG and magazines, there are a couple other calibers that also use the same.

I've always been taught to match a BCG to a barrel and don't switch them out as they can wear differently and cause headspace problems.

 

[staten42]

Very much so. Everything you listed can be run on the same lower without modification.

What caliber out there require modification? What types of modifications are required?

 

[shooter521]

What caliber out there require modification?
What types of modifications are required?

Pretty much any round that will fit into the dimensions of a 5.56 AR mag just requires a barrel, bolt and mag swap. This includes 7.62x39, .458SOCOM, 6.8 Rem SPC, 6.5 Grendel, 5.45x39, .300 Whisper, .204 Ruger, and many others. Pistol calibers (9mm, .40, etc) require the addition of a magwell block, and some may require a different hammer and/or bolt catch. Rounds that are too long to fit in a standard 5.56 AR mag necessitate stepping up to the AR-10 (.308-based) platform.