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KaiserB wrote: The upper receiver is much of the accuracy in an AR 15. You may want to have a gunsmith match up all the parts etc. if you get just an upper receiver.

Just out of curiousity, what's involved in "matching up the parts" that would require a gunsmith? Not being sarcastic at all, I just figured as long as the reassembly was done correctly and the build is solid, the rezero'ing process of whatever sights/optics you have back on the rifle would get it accurate again.

Now if the parts were loose or something, I could see that being a problem...

On the same topic, should I need one, anyone have recommendations for a gunsmith in the Houston area? Is this something a "gander mountain" could handle, or is it more specialized?

135boomer wrote:Another option is to just swap the upper receiver, not the entire upper half. I'm thinking about it too.

[slapping forehead]

Aha - obviously I hadn't done enough research here! I assume something like the top link at

http://cmmginc.secure-mall.com/shop/ind ... 353&cat=30&

would be the right approach? $140 certainly sounds more appealing than $500! :-)

I picked up a used Bushmaster AR15 recently, but it's the type with the permanently attached carry handle (A2?). It came with a low quality scope on a low quality carry handle mount, which I wish to replace. After looking at scope mounting options, it's become painfully obvious that a "flat top" upper reciever is a much better solution for optics mounting.

So... I'm thinking about replacing the upper with another flat-top receiver. I'd like to stay with a recognized upper manufacturer, such as CMMG.

My understanding is that either of these would basically be quick replacement onto my existing AR-15's upper?

The "16" M4 upper" from http://www.fireforeffect.biz/shop/index ... t=3&shop=1&

or

http://www.aimsurplus.com/acatalog/CMMG ... _Half.html

While this is seems like an expensive solution, I think I'll be happer with this setup than trying to get a decent mount on my carry handle, and I'll be halfway (just short a completed lower receiver!) to another AR.

Any comments or suggestions? Is the 1/7 vs 1/9 twist and 4140 vs 4150 steel used in the above two receievers worth the $50 difference in price?