help finding a 20" 1/7 upper

[Aznatama]

I'm new to building my own AR, and I'm wondering if I could get some direction as to selecting an upper. I'm not opposed to building the entire upper, but if a complete factory-assembled one could meet the requirements, then that's more desirable.

I'm looking for a free-float 20" chrome-lined 1/7 twist barrel, with rail attachment points for a flip-up front sight and bipod matched to a flat-top upper receiver. I'm also going to be painting the entire thing, so no need for any fancy finishes.

I also like the looks of the milled uppers w/ the flat angular surfaces. Of course, cost effectiveness is also a consideration.

Any suggestions on where to start my search? Thanks.

[AeroEngi]

There's this but it doesn't meet your free-float/flip-up BUIS requirement http://www.bravocompanyusa.com/BCM-M...urg-gov-20.htm

[Aznatama]

How hard would it be to replace the front sight with a gas block and install a free-float?

[kalieracer]

I have one for sale on the for sale section

[beenawhile]

You could just cut down the front sight / gas block.

[Shovel]

I bought a similar BCM upper 2 months ago and it was very easy to swap the front sight for a low pro gas block and cut the delta ring to install a Samson Evolution rail. There are plenty of videos on YouTube to show you how to do it. The Samson rail uses a standard barrel nut. 15" one would cover the gas block too.

[AeroEngi]

You could just cut down the front sight / gas block.

This.

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[BrassCase]

PSA.

[Hoop]

How hard would it be to replace the front sight with a gas block and install a free-float?

If it's rifle gas and rifle length handguards you don't have to cut the front sight.

Flash hider unscrews with a crescent wrench.

You can do this by hand with a friend who has a strong grip but really a vise and receiver block is best.

You will have to hammer out the pins that hold the front sight base and then slide it forward, remove the delta ring and possibly the barrel nut (will take spanner wrench or AR15 wrench). Then install new handguards. If you played with legos as a kid you should be able to do it. After the new handguard is installed you slide the sight back on.

A new crush washer for the flash hider might be an idea.

[PRODRIVE]

i have a FN m16a4 upper

[hermosabeach]

What bullet weight are you shooting where I want a 1:7 for a 20" barrel?

Colt made or makes a 24" free floated upper for their accurized rifle. I beleive it is in 1:9 twist

This might work-

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=348400082

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=349621677

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=349579588

[Metal God]

http://palmettostatearmory.com/index.php/catalog/product/view/id/13887/s/psa-rifle-length-ss15g2-premium-20-stripped-railed-upper-without-bcg-or-charging-handle/category/320/

http://palmettostatearmory.com/index.php/psa-hammer-forged-stainless-steel-rifle-length-ss15g2-premium-20-stripped-railed-upper-without-bcg-or-charging-handle.html

[Aznatama]

I saw some graphs online, and muzzle velocity appeared to be highest with a 20" for 5.56, while dropping off for lengths longer than 20"

Purpose is to build an accurate 5.56 platform. I know heavier rounds need a faster twist to stabilize, which is why I'm opting for a 1:7 if possible.

I have 2 lowers coming in, and one I'm just going to get a run of the mill M4 upper, but I'd like to make a custom DMR platform.

Thanks all.

[Aznatama]

Any thoughts on the mega or spikes uppers? I really like the look of them over the rounder standard uppers.

[BrassCase]

Check out the comments by the late John Noveske about barrel length:

http://noveskerifleworks.com/cgi-bin/imcart/display.cgi?cat=110