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Are shorter barrels more accurate? - hm2 clark - 01-29-2012
I would think that with all else the same the shorter the barrel the less potential it has to "whip around" as the bullet is leaving the muzzle. Kinda like the shorter the tuning fork is the less it whips around at the tip. Am I right? And if I am right does a barrel that has been shortend 2-3 inches display that worsing accuracy at 400-500 yards.
Are shorter barrels more accurate? - Pancho Villa - 01-29-2012
All else being equal, shorter barrels are more accurate.
You have to be in some pretty niche applications to notice the difference, though. For most shooters other factors (in order: YOU, ammo quality, barrel quality) are far more relevant than your barrel harmonics on any modern firearm.
Are shorter barrels more accurate? - RangerRick - 01-29-2012
At longer ranges like that it doesn't matter because wind becomes dominant. A crappy 2 moa gun will shoot a 20 inch circle at a thousand yards on a dead calm day.
Problem is there are very, very few dead calm days.
An error of 2 mph in doping the wind will throw you off that far at 1,000 yards.
Even if shortening the barrel does have this effect it will be more than offset by the loss of muzzle velocity at longer ranges.
You are probably better off finding a good node for a longer barrel in terms of real world accuracy. That and learning to dope the wind as best you can.
RR
Are shorter barrels more accurate? - noone - 02-04-2012
Barrel length has more effect on velocity than accuracy. There are some tests showing that shorter barrels have a tendency to be a bit more accurate because as the barrel's length is cut, it becomes a bit stiffer thereby reducing barrel whip. However, in an AR15 type platform, there are so many other factors effecting accuracy that barrel length's effect becomes negligible.
Those effects are: moving parts, build quality, gas system type and assembly, receiver stiffness, play between upper and lower receiver, and many, many other items.
If we were only considering bolt gun type pressure barrels locked into a firing device, I would agree that there is a tendency for the barrel to become more accurate as it is shortened. Not so much in semi autos though.
Are shorter barrels more accurate? - bwaites - 02-04-2012
Shorter barrels ARE more accurate, but.....
Shorter barrels of the same diameter will have less whip. BUT....less velocity also.
So, IF you can make the distance so short that velocity has no effect, then the shorter barrel will be more accurate. The problem is finding that distance!
My guess is that at 50 yards, maybe even 100 yards, a shorter barrel will work better. You can see the thought process in Benchrest, where they effectively create less whip by making heavier barrels. It can be carried to crazy extremes, and thus there are weight classes!
We are seeing the facts impact in police marksman rifles, where the chance of a police intervention is most likely less than 100 yards, and the Police are often using .223 or .308's with 20 inch barrels, because velocity at that range is not so critical. Those same shooters, if forced to compete at 1000 yards, will usually push barrels out to 30 inches, or even more, to pick up as much velocity as possible from the calibers. They will have more whip, so then they go to heavier profiles, and the battle rages!
Are shorter barrels more accurate? - elkbow - 02-04-2012
Shorter barrels have a tendancy to be more accurate, however velocity is a big difference between a 16" barrel and a 24" barrel, so affects your tradjectory....
Depending on how far you want to shoot is a factor, stability of the gun, carryability, etc. I got a POF P308 with a 16" barrel as I will keep my shots usually 400 yards or less, so will do what I want, and the 16" barrel is proven in the POF to shoot much better than the 20" barrel. There is a factor of harmonics that can affect accuracy, so if you could test a barrel for your load and go 16, 17, 18, 19, 20, etc. and keep going, you can theoretically find a longer barrel that will have the accuracy of shorter barrel and have the velocity of a longer barrel
Are shorter barrels more accurate? - bwaites - 02-04-2012
elkbow makes a good point. I did not EVEN want to get into harmonics, since some people think that barrel harmonics are closer to witchcraft than science! LOL!
Simply put....Stiffer is better! (In more than one circumstance!)
And when it comes to barrels, shorter is usually stiffer!
Are shorter barrels more accurate? - leopard6.5 - 02-04-2012
If I remember right from the old forum, Bill A. had said that when he was doing the testing for the Grendel, he had found the 18" barrel to be the most accurate.
Hopefully, at some point, he'll be able to jump in and explain it himself.
Lee
Are shorter barrels more accurate? - hm2 clark - 02-05-2012
I was not aware that play between upper and lower receivers affected accuracy. -assuming cheek weld is conststant. Would someone care to ilumanate me?
Are shorter barrels more accurate? - stokesrj - 02-05-2012
My thoughts are that many things affect accuracy, and affect it differently under different circumstances. For the AR platform the most critical element is barrel quality, easily overwhelming the barrel length effects if we limit our discussions to conventional lengths, say 10" to 28". In this range of lengths and when shot from a bench shorter is more accurate. However, as others have stated at long distances velocity can help overall accuracy by reducing wind doping error in a longer barrel. If metallic sights are used longer is better, assuming a solid position to shoot from. However, the reverse is true if an unsteady position is used such as offhand. In this case a shorter barrel is more accurate again because of the reduced barrel time, movement of the rifle before the bullet leaves the muzzle is reduced. Another factor in offhand is wind moving the shooter and the gun, a shorter barrel is again more accurate because the effects of the wind move the shooter and rifle less.
This is why you will see devices such as the Hule Bloop Tube used on match rifles. The barrel length can be increased to 30" for prone positions where a longer sight radius is desired and shortened for off hand and sitting where reduced movement from wind is desired. http://www.accurateshooter.com/gear-reviews/bloop-tubes-from-norm-houle/
Bob
Are shorter barrels more accurate? - elkbow - 02-05-2012
hm2 clark Wrote:I was not aware that play between upper and lower receivers affected accuracy. -assuming cheek weld is conststant. Would someone care to ilumanate me?
I believe it can definitely affect accuracy, but only in certain circumstances. Consider when you shoot, whether it be off-hand, with shooting sticks, on a bench, your hold changes for each one. If you are shooting off-hand you have one hand on the forearm and one on the grip and finger on the trigger, if you have slop between the upper and lower you can twist the two. Granted, the up and down movement and left and right would be the issues, not so much with rotation, which would be minimal. Now another point, the scope is mount to the upper, therefore it reduces the issues with the slop, where I believe it comes in to play the most is inconsistency in stability. To me, if you grab the forearm, and hold the grip, see if you can rock it front to back, not up and down or side to side, front to back is where it could have the highest possibility of affecting your accuracy. If you shot from a bench and there was play front to back, conceivably it could rock and move differently for each shot depending on where it settled last.
Now all that being said, I believe it is very minimal. I have a few AR's bedded, however I did not see any noticeable change in accuracy. If you wanted to shoot really long distances where every bit counts, it may be worth the enhancements to the gun, I just haven't seen any benefit from it.
Are shorter barrels more accurate? - Variable - 02-05-2012
hm2 clark Wrote:I was not aware that play between upper and lower receivers affected accuracy. -assuming cheek weld is conststant. Would someone care to ilumanate me?It doesn't. Kinda like the accuwedge thing. They do nothing to affect mechanical accuracy, and it's been tested multiple times by the military. Armalite used to have a technical paper on it somewhere. I can't find it now, but I wish that paper on the whole upper to lower fit thing was tacked on every AR15 related board in the known universe for perpetuity.LOL!
Are shorter barrels more accurate? - Variable - 02-05-2012
elkbow Wrote:I believe it can definitely affect accuracy, but only in certain circumstances. Consider when you shoot, whether it be off-hand, with shooting sticks, on a bench, your hold changes for each one. If you are shooting off-hand you have one hand on the forearm and one on the grip and finger on the trigger, if you have slop between the upper and lower you can twist the two. Granted, the up and down movement and left and right would be the issues, not so much with rotation, which would be minimal. Now another point, the scope is mount to the upper, therefore it reduces the issues with the slop, where I believe it comes in to play the most is inconsistency in stability. To me, if you grab the forearm, and hold the grip, see if you can rock it front to back, not up and down or side to side, front to back is where it could have the highest possibility of affecting your accuracy. If you shot from a bench and there was play front to back, conceivably it could rock and move differently for each shot depending on where it settled last.
Now all that being said, I believe it is very minimal. I have a few AR's bedded, however I did not see any noticeable change in accuracy. If you wanted to shoot really long distances where every bit counts, it may be worth the enhancements to the gun, I just haven't seen any benefit from it.
FWIW, it's been tested and found to be a complete non-issue. Upper to lower fit only has the ability to affect accuracy insofar as psychological impact on the shooter. If it bugs you, then it likely won't hurt to tighten it up (though I'd never do it on a "down range" gun!).
Uncle Sam sez:
"As per the TM.
1. With the upper receiver attached to the lower receiver, and the pivot pin and takedown pins in place,
perform the following test:
(a) Apply hand pressure to push the upper receiver as far to one side as possible.
(b) Attempt to insert a 0.020 inch thickness gage between the pivot pin lugs or the upper and lower
receivers.
© If the thickness gage penetrates to the pivot pin at all accessible locations, repair by replacement of
the upper receiver (see (b) below) or replacement of rifle is required.
2. If the rifle fails the above test, remove the upper receiver and install a "NEW" upper receiver and perform
the test again.
3. If the rifle now passes the above test, it shall be considered serviceable and continue in use.
4. If the rifle fails the test with a new upper receiver, this failure shall be considered a shortcoming. This
shortcoming requires action to obtain a replacement rifle. Once a replacement has been received,
evacuate the original rifle to depot for overhaul.
3-68"
If someone has an upper that is that loose, then it needs to be corrected/replaced. Otherwise, rock on.
If anyone out there has a copy or a link to the Armalite paper on receiver fit please post it as my google foo is failing me tonight.
ETA: Here is one of them...http://www.armalite.com/images/Tech%20Notes/Tech%20Note%2055,%20Receiver%20Tightness.pdf.
I'm pretty sure AMU tested it also.
Are shorter barrels more accurate? - elkbow - 02-05-2012
sorry, but thats a different circumstance than I was talking about, i said front to back, that is all about side to side or up and down, I said only in certain situations, granted if takes some bad tolerances for it to happen....and it is the same reason why we bed out actions and barrels in our stocks of our bolt rifles....and the same issue, front to back, thats why we have a sequence and torque specs of tightening our action screws on our bolt guns, there is a reason it changes accuracy, and drastically in some cases
believe me, i can make your upper and lower receiver fit affect your accuracy....
I don't think you understand what I am getting at, if you took the same exact setup each time you shoot, it would not affect accuracy, the problem comes in to how you torque the gun, if you can eliminate the slop between the upper and lower receiver, it will make you more consistent in your hold or rest, less torque. It makes it consistent each time. Only the front to rear slop would affect accurace, but the good part is that the tolerances on the takedown pins and holes are very good and I have not seen slop there in a long time.
Think about when you go to the range and what rest you use. I use either a lead sled or a hart front rest with rabbit ear rear. How do you hold your gun? How do you cradle the rear of the stock? Do you make sure that your gun sits perfectly in the front rest after each shot? The more inconsistencies you can eliminate, the more consistent you will be.
Are shorter barrels more accurate? - Variable - 02-05-2012
elkbow Wrote:sorry, but thats a different circumstance than I was talking about, i said front to back, that is all about side to side or up and down, I said only in certain situations, granted if takes some bad tolerances for it to happen....and it is the same reason why we bed out actions and barrels in our stocks of our bolt rifles....and the same issue, front to back, thats why we have a sequence and torque specs of tightening our action screws on our bolt guns, there is a reason it changes accuracy, and drastically in some cases
believe me, i can make your upper and lower receiver fit affect your accuracy....
I don't think you understand what I am getting at, if you took the same exact setup each time you shoot, it would not affect accuracy, the problem comes in to how you torque the gun, if you can eliminate the slop between the upper and lower receiver, it will make you more consistent in your hold or rest, less torque. It makes it consistent each time. Only the front to rear slop would affect accurace, but the good part is that the tolerances on the takedown pins and holes are very good and I have not seen slop there in a long time.
Think about when you go to the range and what rest you use. I use either a lead sled or a hart front rest with rabbit ear rear. How do you hold your gun? How do you cradle the rear of the stock? Do you make sure that your gun sits perfectly in the front rest after each shot? The more inconsistencies you can eliminate, the more consistent you will be.
Well again (FWIW): Per the link I posted above--"The fact is that the bullet exits the bore before movement of the receivers produces a measurable effect."
Regardless of what the shooter does the relationship of the optic/sights to the barrel will not change, and the projectile will have left the bore before the upper moves in any significant way with relation to the lower housing. All I can say is that it has been tested multiple times and no measurable difference in accuracy has ever been detected.
As far as Shooter consistency with relation to position goes, I'd say your lower would pretty much have to be falling off of your upper to affect your position in any measurable way. I hope I don't sound like I'm coming across as an argumentative jerk in the way I'm saying this, it's just that this is the way I've always been taught, and it bears 100% in agreement with everything I have ever observed in the real world as well. I know it sounds counterintuitive (as was noted by Armalite), and that is why this discussion seems to pop up in the AR world a lot. It's just that no reliable source has ever demonstrated a centilla of difference between tight and loose lowers. It has certainly made the makers of the Accuwedge happy though. Kinda like full length guide rods on 1911's, butt plugs on Glocks, and "anti-walk" pin sets on ARs. That is my strongly held opinion at least, and I'm sure not everyone will agree.
Are shorter barrels more accurate? - elkbow - 02-05-2012
it doesn't take but slight torque change in an action screw in a bolt gun to affect accuracy, on an AR, your lower is dangling from your rest, if you have a light trigger and only pull the trigger without holding the grip, there would be little affect in accuracy, if you hold the grip while shoot and there is play front to rear, you can affect accuracy....
this could be argued to death, i've built over 20 AR's and owned I don't know how many, i've seen about everything from cheap parts being good to good parts being cheap, I can't say that i've sat down with each AR and checked for accuracy by adjusting the upper to lower receiver fit, however I have seen where a sloppy front takedown pin affected accuracy twice, and I replaced with tighter fitting pins or used shims from triggershims.com, for most purposes though for the average shooter, they don't care about bedding, shims, tight fighting parts, if their gun will shoot 1 MOA they are good to go, I won't own a gun unless it will shoot .5 MOA or better with my handloads....well I should say that, my stock 450 bushmaster uppers shoot just under 1 MOA with factory ammo, bought the Hornady stuff for $19 a box and don't plan to reload for awhile and haven't spent enough time with my 458 SOCOM, it shoots right at .75 MOA with 300gr TTSX and should have put on one of Marty's barrels, just using the RRA barrel, so might not get down there, but shots will be limited range anyways
I know this could be argued to death, but i'm anal about mechanical stuff, i'm an engineer
Are shorter barrels more accurate? - Variable - 02-05-2012
An AR15 is definitely not a bolt action, and it's receiver isn't being torqued, so I don't personally see any corollary there. With regard to your aforementioned two receivers with sloppy front pins-- I will humbly submit that there may have been more at play in perceived pre/post accuracy than was immediately apparent.
As far as your invocation of pedigree goes: I spent the latter part of my military career as a Combat Arms markmanship instructor in the Air Force, and I've built well over a hundred ARs in civilian life as well. I used to gauge and repair thousands (AF CATM). I don't think that matters at all in this though.... My pedigree won't affect mechanical accuracy. I guess I will just agree with the US AMU, Armalite, Rodman Laboratories and my own personal observation along with many others for whatever that is worth....
I reckon the short form is that: I'll agree to disagree.
Are shorter barrels more accurate? - Bill Alexander - 02-05-2012
I found that the 18" barrel seems to be well balanced with the caliber and in most cases will shoot exceptionally well. For a weapon of given weight the barrel seems to trade weight against accuracy well.
As we have progressed with the Grendel barrels we have observed that the general weight of barrel we have been using is rather heavy. Unless the weight is required for stability on the bags or bipod a lighter barrel may serve much better. This has been slowly proven over a series of years and for 2012 we have re-profiled our entire Grendel fleet. Fluting seems to work well which may be due to the low operational pressures involved.
Are shorter barrels more accurate? - stokesrj - 02-05-2012
elkbow Wrote:it doesn't take but slight torque change in an action screw in a bolt gun to affect accuracy, on an AR, your lower is dangling from your rest, if you have a light trigger and only pull the trigger without holding the grip, there would be little affect in accuracy, if you hold the grip while shoot and there is play front to rear, you can affect accuracy....
this could be argued to death, i've built over 20 AR's and owned I don't know how many, i've seen about everything from cheap parts being good to good parts being cheap, I can't say that i've sat down with each AR and checked for accuracy by adjusting the upper to lower receiver fit, however I have seen where a sloppy front takedown pin affected accuracy twice, and I replaced with tighter fitting pins or used shims from triggershims.com, for most purposes though for the average shooter, they don't care about bedding, shims, tight fighting parts, if their gun will shoot 1 MOA they are good to go, I won't own a gun unless it will shoot .5 MOA or better with my handloads....well I should say that, my stock 450 bushmaster uppers shoot just under 1 MOA with factory ammo, bought the Hornady stuff for $19 a box and don't plan to reload for awhile and haven't spent enough time with my 458 SOCOM, it shoots right at .75 MOA with 300gr TTSX and should have put on one of Marty's barrels, just using the RRA barrel, so might not get down there, but shots will be limited range anyways
I know this could be argued to death, but i'm anal about mechanical stuff, i'm an engineer
Elkbow,
I'm an engineer too, and agree with you in theory, but in practice it just isn't so. I've seen some of the sloppiest fit AR's, ones that audibly rattle, win national championship matches in the hands of the top AMU shooters. I can guarantee you that if accuwedges, bedded or bolted, or just selecting tight fit upper to lowers, made a difference, they would do it, money is no object, time is no object for them. But instead they concentrate on quality components and tuned loads. Even the tuned loads is to the average upper, not an individual one.
The AMU also has a ganged machine rest that clamps the upper receiver into a return to battery recoil guide type of fixture that uses just a trigger housing to fire the uppers, so there is no lower even in the equation. The best shooting one goes to the top shooter regardless of lower fit, that's how they get the sloppy fit to begin with. To them knowing their trigger is a higher priority than the fit, that's also why they shot Geissele High Speed triggers, and as nearly identical as they are they won't trade lowers to get a better fit for fear of changing the trigger release they have trained with.
I know this because I have dryfired some of their rifles and asked how they can live with that slop. They just smile and say look at the scores I just shot with that sloppy fit.
Regardless of all that I still like a tight fit, and have ordered Les Baer matched upper and lower halves for my next build.
Bob
Are shorter barrels more accurate? - elkbow - 02-05-2012
stokes, did you ever read what I said? And why would AMU test like that, why would they eliminate the lower if it has no affect on accuracy?
also, 'regardles of that I still like a tight fit'? why?
guys are you talking about experience or what you read? geez.....
ok, post away, i won't be posting, normally don't get in these debates, i'll stick with what I know and my experience....you stick with what you think or read
I'll leave you with a parting though, if i'm shooting off of shooting sticks, I have loose takedown pins, forearm is on the sticks. First shot I shoot I apply pressure rearward on the grip, second shot I apply pressure forward on the grip, where is the pressure on the upper? any affect?