AR Barrel Length


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StringTwelve
February 3, 2011, 01:41 PM
I just recently started reloading for my AR and after some testing I'm getting my groups down to 1.5" at 100 yrds (from bipod). I currently have a 16" non-free floated, heavy barrel, 1 in 9 twist upper. I have been considering going to a 20" or 24" upper in hopes of tightening that group up even further.
So my question is, how much difference can I expect to see in upgrading to a 20 or 24? Should I go with a bull barrel setup? 1 in 8 or 1 in 9 twist?
I will mostly use this gun for varmint hunting and target shooting and would like to start pushing accuracy on out to 300 and 400 yds.

Thanks

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TonyAngel
February 3, 2011, 02:02 PM
A longer barrel does not get you better accuracy. All a longer barrel will get you is more velocity allowing you to shoot at longer distances, although the distances that you are talking about would be a cake walk even for a 16" barrel.

Assuming that all other things are equal, a shorter barrel will be more accurate than a longer barrel of a like profile. In order to attain the same accuracy with the longer barrel, it will need to be heavier. I also don't think that bull barrels are necessary or desireable.

Many will argue that a bull barrel will take longer to get hot. This is true, but it also takes a bull barrel longer to cool off. I quit using bull barrels a few years ago. I've found that with a quality barrel you really don't lose that much accuracy when the barrel gets hot. Besides, the claim that bull barrels take longer to get hot is moot in a bunch of situations. Frankly, if you are shooting a lot, a bull barrel is going to be just as hot as a standard barrel after 100 yards. The only advantage that I've seen with bull barrels is that the extra weight does help with bounce when shooting from a bipod. On the other hand, having to lug a 24" bull barrel around isn't any fun either.

Lastly, the original post sure sounds like you expect the addition of equipment to improve your shooting. If you are a solid shooter and the equipment is holding you back, then a better barrel my help. If you are just starting out and are still working on your form and technique, you may be wasting you money and setting yourself up for a disappointment.

BTW, if that AR you are shooting is just a run of the mill build with a 16" chrome lined barrel, those were never intended to deliver precision accuracy. If you want precision accuracy get a good stainless barrel.

Bartholomew Roberts
February 3, 2011, 02:04 PM
Not much, if any improvement. All a longer barrel will do is give you more velocity, which will make drop and wind less of a problem at longer distances. At 100yds, it won't do much of anything for you.

In fact, a 16" HBAR is probably going to be more rigid than a 20" or 24" HBAR.

My best improvements to accuracy have been by:
1. Getting a top quality barrel
2. Free-floating

A lot of people recommend a match trigger as well; but I haven't really seen it myself - then again, the one rifle that does have a match trigger doesn't get shot for accuracy often.

Just doing rough calculations, the 20" barrel shooting M193 at 400yds will get you about 5" less drop and 2.5" less wind drift at 400yds compared to the 16" barrel.

mc223
February 3, 2011, 04:18 PM
If your shooting with stock sights a move to optics will likely tighten those groups.
Reloading is a continuous learning process. Changing a barrel will necessitate new load development. Seems better to me to further refine your reloading skills and developed loads.

TonyAngel
February 3, 2011, 04:49 PM
If you really want to dive off of the deep end and start trying to see how tight you can get with an AR, get a good barrel. It doesn't need to be super expensive, just good. Bravo Company SS410 or White Oak should do the trick. Load up some 77gr Sierra Match Kings using plain old Lake City brass filled with 24.1gr of Reloader 15 and sparked off with a Remington 7.5 primer. That is almost a guaranteed sub MOA recipe with a good driver.

If you don't mind dumping the money on a barrel, you could also consider Krieger, Superior barrels, Centurion and Ranier Arms.

StringTwelve
February 3, 2011, 06:12 PM
Thanks for all the input so far. And yes, if I purchase another upper or entire AR with a longer barrel I would want to see a marked improvement. I personally don't want to spend the money for a shiny new bull barreled setup that I now have to lug around when I'm coyote hunting if it's not going to help me all that much.

One of the uppers I have been considering lately is the 20" bushmaster predator. I've actually handled this gun and like the fact that it's not too heavy with the fluted barrel and the free float tube. Does anyone have any experience with Bushmaster barrels?

FYI, I'm already using a Nikon M223 3-12x45.

mc223
February 3, 2011, 06:28 PM
I have a 20 in fluted 1 in 9 Bushmaster that is shot out at 15000+ rds. The leade is along way down the barrel and was still shooting under an inch at 1oo yds when I changed it to another Bushy barrel. I havent used the new barrel much yet.

10-96
February 3, 2011, 06:33 PM
Another comaprison you might try is to shoot a couple of groups with your bi-pod, and then take it off and try another couple. It looks like it may be mounted to handguards that aren't true free-floated. Put the rifle on bags- with them as close to the mag well as possible, and then try some groupings. You may be getting effect from barrel influence. Also, how is the trigger and your trigger discipline, followthrough, etc?

mc223
February 3, 2011, 06:59 PM
So after reading your post in Reloading, I see you have a 14.5 barrel.

The process of welding the Phantom Flash Hider can place stress at the muzzle and the barrel extension can create an unbalanced pressure change to the back of the projectile.
Your current barrel may very well be as good as it can get.


If you want to spend the cash anyway, call John Holliger at White Oak Armament and get fixed up right.

http://www.whiteoakarmament.com/

henschman
February 3, 2011, 07:00 PM
What type of ammo are you using to get those 1.5 MOA groups? That will be the biggest determinant of accuracy (other than your skill as a marksman). 1.5 MOA is actually about the best most folks can hope for out of a factory, non free floated rifle with a chrome-lined barrel shooting surplus ammo. If that's what you're shooting, I'd say you are shooting about as well as the rifle can.

If you want to move to the longer-range shooting, I would indeed recommend a longer barrel for shooting past 300 yards. The 16" doesn't have a lot of velocity after that, which you need to make clean kills on critters out that far (a 5.56 relies on velocity for it's lethality). Plus the velocity helps with wind and bullet drop, as others have said. If you want the utmost accuracy, get a stainless steel barrel. 1/8 is a good twist rate, because you can still shoot the lighter weight rounds like theh 55 grain, but you can go all the way up to a 77 grain (which is probably about the biggest you would want to go, or at least the biggest that would fit in your mag). 1/7's sometimes have poor results with bullets less than 62 grains, especially with longer barrels, though there are exceptions.

StringTwelve
February 6, 2011, 01:31 PM
Thanks for all the input. I found a deal I couldn't pass up at a gun show this weekend so I now have a new Bushmaster 24" fluted, free floated AR added to the family. Also got them to throw in a RRA 2-stage 3.5lb trigger with anti roll pins into the deal.

The 16" has now been converted back to a tactical setup with a Aimpoint red dot. The 24" has the Nikon M223 scope sitting on top of it now.

Now if it would only stop raining here in New Mexico I could head to the range!

Again, thanks for the input.

snakeman
February 6, 2011, 01:53 PM
you might just try floating the barrel. That said I would prefer a 20' over my 16 but that because I have long arms and they just fit me better.

TCU
February 6, 2011, 01:54 PM
its hard to get those rifles submoa. Anyway you will have a better chance with that free floated barrel then you will not disrupt any of the harmonics which will bounce and disperse your shot. the trigger will also help, those stock triggers on the rifle are by no means for precision shooting. The longer barrel will only increase velocity, the round velocity will come into play next. depending on the speed of the vibrations to the time when the round exits the muzzle, is the round dispersion you have to worry about. With a longer barrel the arc will be larger at the muzzle then say a shortened barrel, just find your sweet load.

DougW
February 6, 2011, 02:45 PM
Free floating my 20" HB improved the accuracy greatly. I got a wild hair and changed it out to a 16" HB from Beaver Creek Armory, still free floating. I use this rifle for 3 gun matches, so I have not trird for maximum accuracy. I want to be able to consistently hit an 8" plate at 100 yards, and this rifle will definately do this (if I do my part), getting <2" at 100 yards from sand bags. I am a big fan of free floating. I may try a new trigger group to see how much improvement that can make.

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