Question about my first AR build.

[safetyfast]

I'm in the process of collecting parts for my first AR build. I decided to just watch for deals and buy parts as I can get good deals. My plan is to build a reliable mid size flat top. I'm looking at the following upper and barrel from PSA. http://palmettostatearmory.com/index.php/psa-16-chf-mid-length-premium-upper-without-bcg-or-charging-handle.html is there any downside you can see to this?


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[Dolomite_supafly]

I know several people who have these and are really happy.

 

Personally I would take melonited barrel over a chrome lined one. Also, I prefer 8 or 9 twist over 7 twist for defensive guns.

 

When you get ready to order the bolt I would buy the NiB bolt from AIM Surplus. They are SLICK and super EASY to clean. And the best part is they are as cheap as most other bolts that do not have the NiB treatment.

http://www.aimsurplus.com/product.aspx?item=XAIMBCGNIBBDG&name=AIM+AR%2fM16+.223%2f5.56+NiB+9310+MPI+BDG+Bolt+Carrier+Group&search=nib

They are out of stock now but they are a regular item in their inventory.

[safetyfast]

Thanks. Seemed like a good deal. Also considering their blemished setup for the cash savings. I was leaning toward 1:7 twist to be able to shoot the bigger loads when I want. Is that not a good plan.


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[Dolomite_supafly]

9 twist will stabilize anything up to ~77 grain bullets. 8 twist will shoot and stabilize anything that will feed from a magazine. both 8 and 9 twist barrels will also let you shoot lightweight varmint loads. 7 twist will sling the jackets off of some lightweight bullets. I know a 53 grain SMK will shed its jacket from centrifugal force out of a 7 twist barrel but not out of a 8 or 9 twist.

 

7 twist will also affect a bullet's ability to fragment. The bullet must tumble first in order for the bullet to fragment. With a 7 twist the bullet will likely be over stabilized and not tumble, and in turn, not fragment. Another effect of 7 twist barrels is reduced velocity as well as more barrel wear, affecting accuracy over the long term, compared to 8 or 9 twist barrels. So you are starting out with a bullet that has a reduced velocity and the velocity is what is key to the bullet to fragmenting if it does tumble. The threshold for bullets to fragment is considered ~2,650 fps. So if the bullet you are using is going slower than that when it hits the target it will not fragment even if it does tumble.

[safetyfast]

Interesting. Looks like I need to rethink barrel choice.


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[Spurholder]

OP, you'll be fine with the PSA, or if you want to take a step up, with this (comes with a free BCG):

 

http://www.bravocompanyusa.com/BCM-BFH-16-Mid-Length-Upper-Receiver-light-weight-p/bcm-urg-mid-16lw%20bfh.htm

 

Combined with a blem'd BCM lower, you could "build" a complete mid-length rifle for around $900.

 

Or, if you want to try something different, buy a NIB Colt LE6920...hard to beat $900.00 for a brand new Colt carbine.

 

http://www.impactguns.com/colt-m4-carbine-6920-ar15-16in-6920.aspx

 

A 1/7 barrel will be fine for everything from 55-grain ball up to the special 77's like the Mk-262.   And will work just fine with really great loads like the 55 and 70-grain Barnes TSX loads.

 

Good luck in your search.

Edited October 22, 2014 by Spurholder

[safetyfast]

In looking around, it appears that 1/7 barrels are a lot easier to find. I didn't even notice any thing else at BCM.


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