Get another AR15 or just get a different upper?

[breakingcontact]

So as much as I was excited/into/intrigued by the M1A and the mighty 308 round, in a moment of self reflection, I realized it's an absolute want and not a need.

So then my thought goes to getting another AR15. I like the 223/556 round but I am interested by the 6.8 SPC and.458 SOCOM and other rounds.

What would be the advantage of getting another AR15 vs just buying another upper?

Also, on a separate note, how much different is the M&P Sport to a "milspec" AR15? (I know about the barrel/dust cover/forward assist, but how about the internals?)

Open to general speculation or specific suggestions.

Thanks!

 

[henschman]

You can go ahead and get another upper, but you will probably wind up putting together another lower for it as well! Having just an upper sitting around feels like an unfinished project. Then you get to thinking about how it doesn't cost that much to put a lower together, and then before you know it you have another complete rifle in the closet!

As for the M&P Sport, the main difference between it and a "mil spec" rifle, other than the items you already mentioned, is the barrel. A military rifle will have either a 14.5" barrel or a 20" barrel, while the Sport has a 16". However, it uses the same length gas system as the military 14.5" rifles, which makes it a little overgassed, and therefore sharper recoiling. Also the Sport has a Melonite coated (nitrided) barrel, while the GI rifles have chrome lined barrels. Both processes do the same thing, which is to make the barrel longer lasting and more corrosion resistant than a plain chrome moly barrel, but nitriding generally results in a more uniform sized bore, leading to better accuracy. Also the Sport has a heavier profile barrel than mil spec, which means the rifle will weigh noticeably more. Also the mil spec barrels are individually tested by firing a proof load (an extra high pressure cartdridge) and then magna-fluxing them to see if there are any signs of stress in the metal. S&W doesn't do this on their barrels. However, they do apparently use high pressure tested and magnetic particle inspected bolt carrier groups. I have personally opened a Sport and can say it had an "MP" marked bolt, and the carrier screws were properly staked as per mil spec. Also it had M-4 feed ramps, which is mil spec for carbines.

Hope this helps!

 

[breakingcontact]

Also it had M-4 feed ramps, which is mil spec for carbines.

Nice! Didn't know that!

 

[HorseSoldier]

Nice thing with ARs is that you can spread purchases out -- I'd say start with an upper in a caliber that interests you, get some ammo and see what you think. Then you can always pick up a lower (or build one) later. You might find that a fixed stock works better with a thumper sort of caliber, versus collapsible, etc.

 

[breakingcontact]

You might find that a fixed stock works better with a thumper sort of caliber

I've read this is definitely the move with the 458, how about with a 6.8 SPC?

 

[68wj]

Personal preference, but recoil is comparable with 5.56 so adjustable stocks work fine.

 

[HorseSoldier]

Yeah -- 6.8SPC doesn't present any problems with a collapsible stock. It's a pretty mild shooting cartridge.