Advice on new .223 upper build

[jaxpilot]

I'm thinking of building a new upper for my AR-15 for my next appleseed shoot. I am leaning towards a rifle length gas system, 18", 1:8 twist stainless barrel with a freefloated handguard.

If I use the rifle length gas system, and put the front sight above the low profile gas block, is that any different than a 20" barrel with a rifle length gas system and a standard front gas block sight base?

Shouldn't it give me the same sight radius?

Thanks,
Paul

[sgtmace]

Generally the height is standardized unless noted by the manufacturer. I've got a set of DPMS front and rear set up on a flat top with low front block, free floated tube-works fine. Would suggest a standard A1 or A2 type of sight setup. Other CQP types are designed for quick acquisition and make it more difficult to get that fine aim you want for targets.

[MisterB]

Your sight radius will be the same as a 20" gun, yes.

Just be sure to use a high quality freefloat handguard, if you plan to mount your front sight on it.  Larue Tactical or Danial Defense are good choices.

I personally would run a shorter free float handguard, and have my sight fixed on the gas block, so you don't flex the front sight when you cinch your sling nice and tight. Mount your sling to the handguard, and you won't ever have to worry about sight flex.

[ItsanSKS]

I personally would run a shorter free float handguard, and have my sight fixed on the gas block, so you don't flex the front sight when you cinch your sling nice and tight. Mount your sling to the handguard, and you won't ever have to worry about sight flex.

This is how I have my AR set up, though I have a 20" HBAR model.  When I first got the rifle, I mounted the sling to the standard A2 front sight base, and did not notice any barrel deflection.  Perhaps due to the heavy barrel?   A good friend of mine provided me with a free-float hand guard, so I decided to use it- hey, if its free, its for me!

At any rate, most AR-15's are plenty accurate enough for Appleseed use, without the use of match-grade components, or match-grade ammunition.  It is only when you start moving to Full Distance (200yds +) that some of the deficiencies of the bottom tier rifles begin to show themselves. 

By selecting a 1:8" twist, you are getting the best of both worlds:  you can utilize the heavy, match-grade ammunition (up to 77gr SMK) and you can also utilize the cheap 55gr loads for accurate practice at reduced distances. 

If you are dead-set against getting a 20" barrel (my suggestion), definitely go with the rifle-length gas system, as it is a dramatic increase in sight radius, compared to the standard 16" profile.  Sight radius makes all the difference in the world for accuracy, as anyone who placed the Tech Sights on their SKS can attest. 

Whatever build you decide to go with, my suggestion is the use of a chrome lined bore and chamber.  Up to 99% of malfunctions with steel-cased ammo can be attributed to a non-chrome lined bore/chamber.  Even if you don't intend to shoot Wolf or other similar ammo through your rifle, it is nice to know that you COULD, if you ever had to. 

Those that tell you that you sacrifice accuracy by using a chrome lined bore are not mistaken- you WILL sacrifice some accuracy potential, but I personally believe that reliability and ease of cleaning trump the relatively insignificant loss of accuracy.  Non-chrome lined bores also have a reputation for wearing out pretty quick, and this tends to negate any accuracy gains.  This typically happens within the first 2-3,000 rounds.  Competition shooters usually replace their barrels each season, because of this...

-ItsanSKS

[mtmisfit]

gas system length does not necessarily determine sight radius. There are many rifles with a carbine length gas system and standard sight radius. The gas block does not need to be incorporated into the front sight.

[PHenry]

Call me old fashioned (just don't call me old).

I like the standard A2 config - 20' hbar 1:7 chrome lined / .556 NATO chamber.

That config squeezes the most out of the "varmint" round that .223 is, and will stabilize anything other than a 40g frangible round. It loves xm193 (55gr fmj), but will push a 77 / 80 gr jhp match out past 600 and punch nice clean, round holes in paper.

Sight radius is a huge concern for accuracy - even more so than barrel length, but barrel length greatly affects effective range. 20" is minimum barrel length required for maximum potential of .223 round. The military is now issuing 14.5" M4s and a good 1/3 of powder burns outside of the barrel ,resulting in significant reduction in ballistic energy down range. The 18" with full sight radius that you speak of is a reasonable compromise if you feel that you must have a shorter envelope - sort of a 'dissipator" style. 

In the end, it's always more about software than it is hardware - don't ever forget that!