AR-15 Build - Have a couple questions

[Ranger30-06]

Hello all. I have recently decided to build myself an AR-15 (for the second time ) I have built a lower before, so I'm not worried about that part. The thing is I like the 20" M16 style barrel length as opposed to the short 16" barrel M4 craze that seems to overtake a lot of people.

My question is: is there a significant difference between the two barrel lengths when it comes to velocity and weight/balance of the rifle?

Now the specific information. The upper is being put onto a lower (not sure of which brand yet) but it will have an A2 stock, not a collapsible one. Both uppers have A2 sights and heavy(er) barrels. Also, since the rifle has to comply with NJ laws, both barrels have no bayonet lugs or flash hiders. The only significant differences between the two upper receiver choices is one has a 16" barrel and a carbine length handguard, and the other has a 20" barrel with a rifle length handguard. Thanks for the help guys.

 

[Z-Michigan]

Velocity: you will gain 100-150fps with most types of ammo. You can look up chrono results for both 16" and 20" barrels using google.

Balance: depends on the barrels. USGI A2 profile 20" barrels are fairly light and balance pretty well. They would feel only slightly heavier than a mid to heavy profile 16" barrel, and moderately heavier than a M4 profile 16". Compared to a pencil 16" there is a noticeable difference. Heavy profile 20" barrels are awfully heavy and not ideal for any offhand shooting. In all cases being able to put your left hand farther out on the longer handguards helps offset the added weight. You may have limited options in finding a plain muzzle 20" barrel with an A2 or lightweight profile, but it will absolutely be worth the effort. If you just can't find that, you may want to take a relatively common A2 barrel with a threaded muzzle and either permanently attach a brake, or have a gunsmith cut off the threads and recrown the barrel (it would be about 1/2" shorter).

 

[madcratebuilder]

My question is: is there a significant difference between the two barrel lengths when it comes to velocity and weight/balance of the rifle?

Generally you see 50fps per inch of barrel length, there are many variables involved.

The 16" well swing faster and be about a half pound lighter.

 

[Ranger30-06]

Alright, that brings me to the next question then:

Is an extra 200 FPS actually going to make a difference inside of 200 yards? That's about the longest shot I will probably will ever be able to justify with a .223.

Also, is an extra 1/2 pound going to make a real difference. Not to brag here, but I'm 6' 230 lbs and most of that is some serious muscle. A 1/2 pound means almost nothing to me. Heck, my Saiga weighs just about 10 lbs all loaded up, and even that doesn't bother me the least.

And even though the 16" may swing faster, is the balance going to be way off?

Finally, will a 16 inch M4 type top like this even look right on an A2 stocked lower? (as opposed to this upper) Pictures anyone?

 

[ugaarguy]

Is an extra 200 FPS actually going to make a difference inside of 200 yards?

Even with 55gr FMJ and a 14.5" bbl the velocity loss inside of 300 yards won't make a difference. If NJ lets you use ballistic tip bullets then it really won't matter.

Also, is an extra 1/2 pound going to make a real difference. Not to brag here, but I'm 6' 230 lbs and most of that is some serious muscle. A 1/2 pound means almost nothing to me. Heck, my Saiga weighs just about 10 lbs all loaded up, and even that doesn't bother me the least.

It's not the amount of weight, as much as where that weight is - on the far end of the barrel, furthest from your hands, where it has the most leverage against you. (This why you're seeing the move toward folks running rifle length FF tubes & quad rails on 16" bbls: it allows you to get your support arm way out in relation to barrel length, and really change the balance to your advantage.)

And even though the 16" may swing faster, is the balance going to be way off?

No. You can always get the slightly shorter A1 stock later if you think it looks better. You can even get really stubby A2 style fixed stocks like the RRA entry stock if you like that look.

Finally, will a 16 inch M4 type top like this even look right on an A2 stocked lower? (as opposed to this upper) Pictures anyone?

There were plenty of them set up that way during the Federal AWB, and they definitely grew on me. I think the A2 stock looks better than the M4 style stock that's permanently pinned at the fully extended position. The ACE skeleton stocks also look nice in fixed stock applications.

 

[Tirod]

As explained, that's why I built my AR, Post #429: http://68forums.com/forums/showthread.php?17898-6.8-rifle-picture-thread-2011/page43

Moving up to an alternate cartridge specifically designed to increase power 40% makes up for a shorter barrel. Food for thought.

 

[Ranger30-06]

Sorry, but there's just no way I can afford shooting a lot of 6.8 SPC. This rifle is mainly going to be a fun rifle for me, as well as a short-medium range "Oh crap it's happening" rifle. I've already decided that I absolutely want iron sights.

Does a quad rail look retarded on a 16" barrel with A2 sights and an A2 stock? I cant seem to find any pictures of people that have done it. I would like to put a foregrip on eventually, but it isn't mandatory.

 

[gotigers]

No AR looks retarded, except those mall ninja arrangements. In states that don't allow adj stocks, it is probably common. Look at ar15.com's build it yourself forum. There are pic threads that might have the arrangement you want. I see no reason not to put a quad rail on a 16" with an A2 stock. The Daniel Defense Omega would be a good choice.

With the A2 front i would get A2 rear as well. Either a carry handle or a fixed A2 rear BUIS, http://www.aimsurplus.com/product.aspx?item=XDD11002. The A2 system is great using the IBSZ, ar15zeroing.com.

 

[Ranger30-06]

Ok all I have decided on the 16" A2 upper! I'll probably be ordering it this week.

My plans later on are to install an ACE skeleton stock and a quad rail forend to attach a foregrip. I'm not really into the "tacticool" thing and bolting on 30lbs of accessories, but I like the better handling that you get with a foregrip and the ACE stock looks a lot better than a normal A2 stock then while I was at it I saw a picture of an ACE stock with a quad rail forend and I was like "Wow! That really looks good!" Ill post pictures as the project comes along.

 

[ugaarguy]

Ranger, if you want to stay light weight you might look into the MagPul MOE forearms. They look nice, and they keep the weight down. The slots are thin, so you can easily mount little pieces of MagPul factory (of aftermarket) plastic or metal picatinny rail to mount small accessories like fore-grips on them. Pics in links on MagPul site:

MOE Hand Guard - http://store.magpul.com/product/MAG440/49
MVG - MOE Vertical Grip - http://store.magpul.com/product/MAG413/39

 

[Ranger30-06]

I'll keep those in mind. I'm not so much concerned with "lightweight" as "overly-heavy." My Saiga .308 is ~9lbs loaded so I doubt that this AR with no lights/lasers will get even near the weight of the Saiga. Thanks for the suggestions though!