In an AR varminting platform, does barrel length affect accuracy?

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BringHomeTheBacon

BringHomeTheBacon

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Consider varmint rifles from Rock River Arms. A woodchuck gun already custom-built from the factory. 24" vs 20" vs 18" vs 16". Will the 20" barrel have an accuracy advantage over the 16" barrel? Why a handy carbine for chucks? With a pic or weaver rail, can instantly go from varminter to home defender by changing sight systems. I would want mil-spec sights for home defense and a varmint scope for varmints. These Rock River AR's hover around $1,300 in price. Might as well get two guns in one if accuracy is good enough in the shorter barrel. The Rock River varmint ARs also features a Wylde chamber. Supposedly, it can handle 5.56 and .223 equally well.



This video above is claiming 5/8 MOA with a 20" barrel.

Varmint A4 (rockriverarms.com)

Rick River Arms claims 3/4 MOA for both the 16" and the 20" versions. 3/4 MOA is good for woodchucks out to how far? How far for prairie dogs? Ground squirrels?

The RRA varmint versions also feature the Elevated Optical Platform. The receiver pic rail is higher than the handguard pic rail. I'm not sure if there is even an iron sight system available for this particular gun model. Uneven rail heights from fore to aft. Tactical ARs tend to be true flat tops. The picatinny/weaver rail system is flush from front to rear.
 
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Accuracy is a function of barrel quality and having the correct rifling rate for the bullet used. This assumes your not using iron sights.
A longer barrel will give incrementally higher velocity which affects bullet drop, making range estimation less important. AR barrels between 16-20 inches seem to be favored for handiness and velocity. Shorter barrels will give the shooters and bystanders greater muzzle blast.
 
BringHomeTheBacon said:
Consider varmint rifles from Rock River Arms. A woodchuck gun already custom-built from the factory. 24" vs 20" vs 18" vs 16". Will the 20" barrel have an accuracy advantage over the 16" barrel? Why a handy carbine for chucks? With a pic or weaver rail, can instantly go from varminter to home defender by changing sight systems. I would want mil-spec sights for home defense and a varmint scope for varmints. These Rock River AR's hover around $1,300 in price. Might as well get two guns in one if accuracy is good enough in the shorter barrel. The Rock River varmint ARs also features a Wylde chamber. Supposedly, it can handle 5.56 and .223 equally well.



This video above is claiming 5/8 MOA with a 20" barrel.
I had the same rifle pictured from RRA and it was a hole in a hole shooter with the right ammunition and me doing my part. I sold it to a buddy who moved out to west Texas and planned on doing his part of lowering the Prarie Dog population.
Varmint A4 (rockriverarms.com)

Rick River Arms claims 3/4 MOA for both the 16" and the 20" versions. 3/4 MOA is good for woodchucks out to how far? How far for prairie dogs? Ground squirrels?

The RRA varmint versions also feature the Elevated Optical Platform. The receiver pic rail is higher than the handguard pic rail. I'm not sure if there is even an iron sight system available for this particular gun model. Uneven rail heights from fore to aft. Tactical ARs tend to be true flat tops. The picatinny/weaver rail system is flush from front to rear.
Click to expand...
 
Assuming equal accuracy from both barrels, a longer barrel will let you shoot farther simply by virtue of the increased velocity.

I've shot out past 500 yards with my 16". Honestly, I can't remember the last time I needed more than a 16" barrel. I would think that making long shots on small targets would have more to do with the trigger and the scope than barrel length.

And, of course the ammo. Just because they say it will shoot .75 MOA doesn't mean it will do that with all ammo. I have a 16" that will shoot sub MOA all day long with a good 77 grain load, but only does 1.5 MOA with M193 or 855.
 
I'm no expert, but depending on the metal, you can get whip in a barrel. Barrel harmonics is the usual term I hear tossed around.

There is a school of thought that a long barrel can give you more velocity and sight radius if using irons, but can be more risky to get barrel movement the longer it is.

I don't know if there is a sweet spot for your specific load velocity, barrel metal and thickness to have "perfect harmonics".

Or who knows, maybe that's all just myth because I'm not a scientist.
 
If using iron sights it is possible to aim more precisely if the front and rear sight are farther apart. That is why you see long barrels on rifles used with iron sights in the Olympics and other shooting sports.

But the mechanical accuracy isn't usually effected. Barrel stiffness could be a factor. Generally stiff barrels are more accurate. A longer barrel will need to be thicker to be as stiff as a shorter barrel. That could make a minor difference.
 
BringHomeTheBacon said:
can instantly go from varminter to home defender by changing sight systems.
Click to expand...
One can go from a 29” 6mmARC target competition upper, to a 20” 204 Ruger varmint upper, to a 16” 223/5.56 home defense carbine, to a 10” 450 bushmaster hunting pistol, with nothing more than unlocking two pins and changing the upper.
Sights stay with the barrel. No loss of zero. All on the same lower receiver.
————
Barrel harmonics.
A barrel’s length has less to do with accuracy than its stiffness. All barrels vibrate, from the instant the pin strikes the primer to long after the bullet leave the muzzle. A stiffer barrel will vibrate faster, spending more time in an area of accuracy called the “node”, than a more flexible barrel. A less stiff barrel has more time at the long ends of the vibration wave, where it is not pointing to where it’s aimed, the waves will also be of greater magnitude.

While velocity is important, it has little to do with accuracy, and everything to do with trajectory.
A fast bullet spends less time being influenced by wind and air pressure, resulting in less drift, making less need for correction.

A long barrel allows a longer push on the bullet from the propellant gases making for faster speeds, needing less correction. Easier for the shooter, not more mechanically accurate.
 
Demi-human said:
One can go from a 29” 6mmARC target competition upper, to a 20” 204 Ruger varmint upper, to a 16” 223/5.56 home defense carbine, to a 10” 450 bushmaster hunting pistol, with nothing more than unlocking two pins and changing the upper.
Sights stay with the barrel. No loss of zero. All on the same lower receiver.
————
Barrel harmonics.
A barrel’s length has less to do with accuracy than its stiffness. All barrels vibrate, from the instant the pin strikes the primer to long after the bullet leave the muzzle. A stiffer barrel will vibrate faster, spending more time in an area of accuracy called the “node”, than a more flexible barrel. A less stiff barrel has more time at the long ends of the vibration wave, where it is not pointing to where it’s aimed, the waves will also be of greater magnitude.

While velocity is important, it has little to do with accuracy, and everything to do with trajectory.
A fast bullet spends less time being influenced by wind and air pressure, resulting in less drift, making less need for correction.

A long barrel allows a longer push on the bullet from the propellant gases making for faster speeds, needing less correction. Easier for the shooter, not more mechanically accurate.
Click to expand...

Changing whole uppers to go from defender to groundhog gun seems more expensive than just changing out sights. I would think the modern picatinny or weaver rail system would be precision enough to allow quick changes of sight systems without any appreciable loss of zero. In self-defense scenarios, sight radius is a moot point. Your shots will probably never exceed 25 yards in a tactical situation at home. Iron sights are preferred over scopes in most tactical situations one might encounter at home. Many such shots may be close range. The army's M4 carbine is 14.50". This is still a battle rifle with such a short sight radius. I just don't know of the Elevated Optic System lends itself to a quick sight changeover system between scope and iron sights. It sounds like a VARMINT rifle might only be good for varmints. Again, it just might be more feasible to have a separate upper for home defense. In that case, it might just be better to have a longer barrel for the varmint upper.
 
As has been covered, very long barrels can be accurate, and very short barrels can be accurate, so I really wouldn't put that much thought into it from an accuracy persepective. The big difference is weight and handling and muzzle velocity. My personal varmint AR is 20" and I think that is the sweet spot for an AR to balance handling, velocity, and noise. A 16" 223 has an awfully loud muzzle report without a suppressor or krink brake and gives up usually about 100-200 FPS muzzle velocity compared to a 20" barrel. From 20 to 24 will put up like 50-100 or so more FPS but its diminishing returns. I find a 24" AR15, especially a heavy barrel one, to be really ungainly and front heavy to carry and shoot. AR15's tends to get pretty heavy already and an 11 lb AR just isn't really interesting to me. My favorite length for an AR is 16" as they just handle and carry so nice, but I am willing to compromise at 20" for a varmint AR for the extra velocity and reduced muzzle blast.
 
Had a DPMS Sweet 16 bull barrel long ago, built a CR6724 years later with fluted bull barrel. Seems to be a wash from 16 to 24 RE: accuracy. Shorter = stiffer while longer = tad more velocity. The 16" bull barrel to me is kinda odd cause it's still too heavy for a walk around unit. With the 24", at least you know you're going from the truck to the bench, not tempted to hump it around. Optic takes sight radius out of equation.
 
BringHomeTheBacon said:
Changing whole uppers to go from defender to groundhog gun seems more expensive than just changing out sights. I would think the modern picatinny or weaver rail system would be precision enough to allow quick changes of sight systems without any appreciable loss of zero. In self-defense scenarios, sight radius is a moot point. Your shots will probably never exceed 25 yards in a tactical situation at home. Iron sights are preferred over scopes in most tactical situations one might encounter at home. Many such shots may be close range. The army's M4 carbine is 14.50". This is still a battle rifle with such a short sight radius. I just don't know of the Elevated Optic System lends itself to a quick sight changeover system between scope and iron sights. It sounds like a VARMINT rifle might only be good for varmints. Again, it just might be more feasible to have a separate upper for home defense. In that case, it might just be better to have a longer barrel for the varmint upper.
Click to expand...

You can get a basic 16" 5.56 upper for self defense in the 200-300 range. That's seams like a much better option then swapping around sights and potentially loosing my zero every time I go hunting.

https://www.bearcreekarsenal.com/gu...ist-carbine-12-handguard-sch-nrail-upper.html
 
This is just my experience and I'm sure other posters will claim otherwise, but a shorter barrel, let's say 16", should have the capability of being more accurate, than a longer barrel, let's say 24-26", because of barrel harmonics ( i.e. twist, whip, and torque, etc). However, 16" and shorter barrels can also result in significantly reduced velocity in some chamberings and may not allow for full effective powder burn. So, it depends.
 
Changing optics back and forth is a bad idea

Bad to keep a consistent zero, especially if you're so worried about accuracy.

But also takes longer than swapping uppers. Takes two captive pins, maybe 15 seconds to swap an upper

Swapping optics will normally require tools, and QD mounts may or may not be effective and efficient.

If you're looking for the be-all-end-all-for-all-things... Probably won't find it and everything is a compromise
 
BringHomeTheBacon said:
Again, it just might be more feasible to have a separate upper for home defense.
Click to expand...
I don’t know if anyone using a 26 inch barrel for home defense.;)
As an aside, neither of my HD-able rifles have iron sights. If the Red Dot fails, like you say, it’s close enough I won’t need it.

Be sure when mating a shorter than 16” inch barreled upper to a lower receiver that it is a pistol lower receiver or has an SBR tax stamp.
 
You know, barrel harmonics can change when you shorten the length of a barrel. That is true. So, the load you had worked up for the barrel at 22" may not work quite right at 16" but that isnt' because the barrel has been rendered less accurate. It is because the load is no longer appropriate. This is a significant point. Work up the proper load and you should be good to go so long as the barrel was shortened and crowned properly.

People have found that their very accurate loads work fine in one rifle, but not in a 2nd rifle (same type of rifle with same barrel length) but that the 2nd rifle in which the first rifle's load don't work is just as accurate with a slightly different load.
 
JeeperCreeper said:
Changing optics back and forth is a bad idea

Bad to keep a consistent zero, especially if you're so worried about accuracy.

But also takes longer than swapping uppers. Takes two captive pins, maybe 15 seconds to swap an upper

Swapping optics will normally require tools, and QD mounts may or may not be effective and efficient.

If you're looking for the be-all-end-all-for-all-things... Probably won't find it and everything is a compromise
Click to expand...

Well, thank you folks. It sounds like having two swappable uppers is the way to fly going between gophers and burglars. I was in the army. I fired an M16 and scored expert. This was a 20" barrel with mil-spec iron sights: rear peep. This is what I am accustomed to for battle. The scope is what I like for long-range hunting. But for countering bad guys, at close range, one can hurriedly aim right over the front sight post for a burglar in the home. The American military went from the M16 rifle to the M4 carbine for a shorter, lighter more wieldy service rifle. Urban warfare in buildings up close has become more trendy in modern times. That and the firepower only an AR can give. Accuracy is not such a big deal for home defense. Handiness, reliability and firepower is.
 
I built a M16A2 clone rifle to closely resemble the one my uncle let me carry overseas years ago. The main difference is the detachable carry handle and no three round burst. I really enjoy shooting it, it seems to shoot a little "softer" than the M4 style carbines I've built. I think this is due to the barrel length/gas tube length. I t was one of the first AR's I built and shot some of my early handloads through so I have some nostalgia there. That being said, I do like the shorter package of the carbine. It's a different gun, but when I have to terminate predators in the chicken coop, I reach for a Youth model (shorter barrel and stock) 20 gauge. Easier to move around walls, trees, etc. Like has been said, pull two pins, change the purpose of the tool, including the optics package.
 
citizenconn said:
a shorter barrel, let's say 16", should have the capability of being more accurate, than a longer barrel, let's say 24-26", because of barrel harmonics ( i.e. twist, whip, and torque, etc).
Click to expand...

Twist, whip, and torque aren’t “harmonics,” and really, twist and torque would be the same thing, but it’s true to say that shorter barrels for a given contour are stiffer than long barrels.

It’s also true to say they have more supersonic oscillations and are more sensitive to “harmonics” since the impulse transverses the length more times.

When guys talk about harmonics changing with shorter barrels, I kind of laugh. We’re talking about exceptionally fast frequencies, such barrel length really doesn’t have anything to do with this. Given a load in the right node, it’ll be happy in barrels varying in length sometimes 3x. Different barrels often like different nodes, this is a fair claim, but it’s not apt to say shortening that same barrel will completely disrupt its “harmonics.” Too many of us have proven that doesn’t happen, whether when we cut down barrels, set them back, or develop loads which work in a multitude of barrel lengths - it’s like a marathon versus the diameter of the Earth, you can cut the Earth in half and the marathon is still a marathon, because it’s so much smaller than the scale of the Equator.
 
What kind of distances are we talking with these woodchucks?

I'm getting up in age and my tired bones like things light and easy. I'd go as light and short as possible. I also wouldn't be swayed by marketing ploys such as the use of the word "Varminter." Just because it has a long heavy barrel doesn't make it excel at killing varmints. Ideally, if I was going varminting at a distance that a 12.5", give or take, barrel can do I'd go that route and put a suppressor on it. My 11.3" build sees a whole lot more action than my 16" does.

Maybe if we knew what the specific task was, we could make more specific recommendations.

5.56 may not be the best thing for the job. Assuming 3/4 MOA accuracy, that's about 3/4" at 100 yards. Twice that at 200, 3X's that at 300 and so on. Again, assuming that your shots are spot on every time.

I've gone wood chucking once in my life. We were doing like 300 yards. I was using a bolt gun in .223 shooting 80 grainers, I think they were. I had a lot of glass on the rifle too, 5.5-22X Nightforce and a Jewel trigger (maybe is was a Timney). That rifle was capable of putting 5 rounds into one hole at 100 yards. I haven't seen too many ARs do that. Not while being fed from a magazine anyway. With that kind of accuracy, it gives the shooter a little room for a margin of human error.

I don't know what your finances are like, but truth be told, my very first AR, which was MANY ARs ago, was a Bushmaster Varminter. Now, in hindsight, I'm almost embarrassed to admit that I paid as much money for it as I did. Knowing what I know now, it had a hacked off front sight for a gas block and it wasn't even pinned. Set screws. The two stage trigger went to crap within 2000 rounds.

I think that for the money, you can do better. Depending on how far you need to shoot or, more specifically, whether you need the extra velocity, I'd go with a 16". I don't know what their complete uppers are like (I don't even know if they sell complete rifles), but the Ballistic Advantage barrels shoot really well if you feed them what they like. Not the bottom of the line government barrels, but the stainless hanson profile barrels.

I think there are other names out there that you could look at too. Depending on money, Noveske and Triarc come to mind. I only mentioned BA because I've been using their hanson barrels for a while now and they never cease to amaze me. I love the profile. My 16" BA barreled AR, which is heavier than my 13.9" Sons of Liberty build, swings like it's lighter because of where the weight is.
 
Varminterror said:
Twist, whip, and torque aren’t “harmonics,” and really, twist and torque would be the same thing, but it’s true to say that shorter barrels for a given contour are stiffer than long barrels.

It’s also true to say they have more supersonic oscillations and are more sensitive to “harmonics” since the impulse transverses the length more times.

When guys talk about harmonics changing with shorter barrels, I kind of laugh. We’re talking about exceptionally fast frequencies, such barrel length really doesn’t have anything to do with this. Given a load in the right node, it’ll be happy in barrels varying in length sometimes 3x. Different barrels often like different nodes, this is a fair claim, but it’s not apt to say shortening that same barrel will completely disrupt its “harmonics.” Too many of us have proven that doesn’t happen, whether when we cut down barrels, set them back, or develop loads which work in a multitude of barrel lengths - it’s like a marathon versus the diameter of the Earth, you can cut the Earth in half and the marathon is still a marathon, because it’s so much smaller than the scale of the Equator.
Click to expand...

What MOA is needed for:

-woodchucks
-ground squirrels
-prairie dogs

at:

-200 yards?
-300 yards?
-400 yards?
-500 yards?

I only went varminting once in my 58 years. It was at a man's private ranch in northern California. 1996. Mid-October afternoon. My successful guided deer hunt was that same morning. Ground squirrels. Sporting my new-then Browning A-Bolt II BOSS in .25-06 with Leupold 1.75x6x32 scope, and Federal Premium 117 gr. SPBT, I was able to connect with these critters 50% of the time standing up in the field and maybe using a fence post as a rest once or twice. The animals were about 100 yards max and the rifle grouped 1 MOA right on the money at the bench offhand. Using prone position, a bipod or a bench in the field, I would expect my shooting to get even better. I already have a new unused Busnell Banner 3x9x32. I bought a new Ruger American Ranch in 5.56 in 2020, but got rid of it last year not even fired once coz it was junk. During cycling tests, the damn thing was difficult to close the bolt on live rounds and also difficult to extract them. I sent the gun into Ruger once but to no avail. The ejected cartridges were also marring the finish on the ejection port area. The gun had a cheesy matte finish and a cheesy plastic stock and my heart just went cold for it. I don't fancy paying 1,000's for a fine custom bolt-action rifle so I figure a good AR gun built for varmints would be feasible. A Buick was once a poor man's Cadillac. An AR built for the chuck field is a poor man's varmint rifle. The Ruger American is something of a Ford Pinto or should I say a Chevy Vega for lack of overall quality.

Ideally, I would like to limit my shooting to the rifle and load's point blank range. This will vary by the size of the kill zone on the target's body. I tend to aim center of mass on such small animals as rodents.
 
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The QUALITY of the barrel and how it acts with specific rounds is more important than the length. It is also very important to know the muzzle velocity with that specific round, and how it drops over various distances. I have built 1.5 MOA AR's using 16" DPMS 1:9 barrels that weren't designated "match" or anything like that, and I have one that is a 16" Larue that is a solid 1 MOA rifle (my old 3 gun rifle).
 
My primary prairie dog rifle is a 240 Ruger AR-15 with a heavy 26" barrel. I probably do not get any additional velocity advantage over a 24" barrel. It shoots fairly flat out to 600 yards or so with 40 grain bullets and is flatter than a 223 Remington so less sight adjustment.

The rifle is heavy, 12-13 pounds empty so not a good walk-about rifle but my p-dog shooting is from a fixed position.

I also have a 24" 204 Ruger AR-15.

I've been dabbling with a 22x6.8 SPC AR-15 and a 22 Nosler AR-15, both with a 24" barrel to see if I can improve things over the 204 Ruger but I've not played with them for a couple years.

For a walk-about rifle, I'd go with a 20" barrel, probably not as heavy profile barrel as my long barrel AR-15's. The lighter barrel would be easier to carry. The trade off for using a lighter profile barrel is it can be shot fewer times before it heats up and needs to be cooled.
 
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