Author Topic: Barrel Length, What's Best? (Read 3155 times)

Bama Bill · « **on:** February 05, 2009, 07:03:19 AM »

I am curious about the effects of barrel length on bullet performance ... velocity ... stability, etc. For example, I have a 45-70 with a 34" barrel ... does a barrel this long actually impede maximum bullet speed? Aside from sight-radius advantages, is a long barrel good for accuracy?

Empty Quiver · « **Reply #1 on:** February 05, 2009, 09:59:06 AM »

As a general rule shorter barrels will be stiffer and more accurate. Longer barrels will generally yield the best bullet speed. If you are using a scope, short barrels give up very little. With open sights a longer sight distance will be more beneficial. For my money I like a shorter barrel, more due to handling characteristics than any percieved accuracy benefits. I figure either length can be made more accurate than my skills will reveal.

Bama Bill · « **Reply #2 on:** February 05, 2009, 12:14:41 PM »

Thanks E.Q. I agree with you about the barrel "whip" associated with longer barrels and the advantage of sight radius is, of course, irrelevant when using a scope ... but, do you know at what point velocity is maximized and at what point barrel length actually begins to slow down the projectile? When does velocity of the bullet begin to adversely affect flight characteristics and reduce accuracy ... or, does it?

Lone Star · « **Reply #3 on:** February 05, 2009, 04:11:30 PM »

The answer is - it depends. In the case of the .45-70 using black powder the 34" barrel will give higher velocities than a 24" barrel for example. But for most smokeless loads that extra length does not usually translate into much usable additional velocity. Obviously the slower the powder, the more velocity difference between the two lengths, but still not a lot. With some faster powders there may even be a velocity loss at 34"

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Bama Bill · « **Reply #4 on:** February 07, 2009, 08:59:50 AM »

Thanks, Lone Star. My suspicions were more-or-less along the lines of your remarks. I guess I'll have to get a chronograph and run some tests. I have a Ruger Single-Shot in 45-70 ... 22" barrel that I can use for comparisons with the "Quigley Down Under" Sharps. I'm still curious about the accuracy aspect of my initial inquiry. I've noticed that most "match" ammo has less velocity than comparable hunting or tactical loads ... and, yet, for example, the super fast .17 HMR is very accurate. So, I'm confused ... does bullet velocity hamper or enhance accuracy?

Autorim · « **Reply #5 on:** February 07, 2009, 05:18:46 PM »

There are many variables. Accuracy does not relate to velocity as much as barrel quality, bullet quality and consistent loads. The accuracy potential of most cartridges is usually reached at less than maximum loads, but there are always exceptions. Every firearm is different.

Most straight wall cases such as the 45-70 will perform best with faster powders. IMR 4198 is hard to beat.
I have chronographed a lot of loads, but have not compared a long barrel and short barrel in the same caliber except in handguns. I will be interested if you do a comparison test.

Some rifles and cartridges perform well over a wide velocity range and some don't. The 45-70 is easy to load and should perform well for you over a wide velocity range and with a wide range of bullet weights. The point of impact may change significantly.

Just guessing, I would bet that maximum velocity with IMR4198 in the 45-70 could be reached in a barrel less than 34 inches.

surveyor47 · « **Reply #6 on:** February 07, 2009, 05:48:46 PM »

My cheap version of the Quigley Sharps is a T/C Encore Custom Shop 26" medium heavy barrel with sights. I replaced factory sights with a Williams Firesight front sight and a Williams Foolproof Target Model receiver sight. This really is a fun, well balanced set up. The 26" barrel prefers 405 grain Remingtons, whereas my 24" Encore barrel prefers 300 grain Remingtons. All things being equal, I find that I hit much better with the 26" barrel. I consider the 24" barrels to be carbine barrels.

jro45 · « **Reply #7 on:** February 13, 2009, 11:38:04 AM »

I like the 26" barrel on rifles. Had a 36" barrel on a 10ga seems like the shot slowed down so I cut it down to 28" its alot better now.

BBF · « **Reply #8 on:** February 14, 2009, 05:21:51 AM »

I don't see any possible way for a bullet to slow down in a barrel unless it is as long as a naval gun and then only maybe. The bullet would have to be moving faster inside the barrel then then gas column behind it.
As long as there is pressure in the barrel the bullet will accelerate. If the peak pressure of a given firearm is reached at 8 " from the breech it isn't zero when the bullet is 22 or 24" down the tube.

Lone Star · « **Reply #9 on:** February 14, 2009, 06:43:08 AM »

Modern peizometric data disproves your assumption, kinda. The chamber pressure peaks soon after bullet movement, then tapers off rapidly as the bullet moves down the barrel and the powder cools and looses energy. A "fast" powder peaks early and its pressure falls very rapidly - meaning its velocity drops off as well. When the gas velocity is below that of the bullet, the bullet will slow due to frictional losses with the barrel. This would require a very fast propellant and a large bore volume - the .45-70 with light loads fits the bill. Using 9.0 grains of Unique and a 400-grain cast bullet ( a popular low-recoil target load) velocities out of my 16.25" Contender are about 50 fps faster than the same load out of my 32" rollingblock.

BTW this phenomenon was well known prior to the invention of digital pressure measuring equipment. .22RF ammo often gave higher velocities out of an 18" barrel than out of a 28" barrel. The reason? Pressure had dropped off enough that friction took over as the main force on the bullet.

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Oldshooter · « **Reply #10 on:** February 14, 2009, 07:02:09 AM »

This is very unscientific but I was always told that the barrel length only need be as long as it takes to burn the powder in the cartridge. Hence .22 Lr needs about 18 inches and a blackpowder rifle in say 50 caliber is considerably longer. any longer and you sacrifice efficiency. My 2 cents

mcwoodduck · « **Reply #11 on:** February 14, 2009, 08:47:45 AM »

I agree with oldshooter to a point.
Yes you are going to get your greatest velocity out of a barrel that is just long enough to burn up all of your powder. And when talking about accuracy what levels are you talking and over what distance. A bullet with it's fastest velocity will have a flatter trajectory than the same load slower and if your talking point of aim point of impact than the faster bullet will seem more accurate. But will it be consistant?
But back to the question, with Iron sights the longer your sight radius is the more accurate the gun will be. The other added advantage is the longer barrel will added weight. You know the whole gravity thing. A body at rest, well a greater force will be needed to move the longer/ heavier gun making it more accurate with optics. I am assuming you are shooting with the rifle loose in your hands off oa rest. Off hand you have the same situation that it will take more force to move the rigle latterly but more force pulling it down. It would be something to see bolted down actions and let's say 308 or 30-06 and the effects of accuracy when going from legal 16" to 26" or longer.
I do not know about giving the bullet more revolutions in the barrel would make it more accurate or not. But I do know that my CZ 452 Lux is more accurate than my buddies CZ 452 scout 16" (in an American models stock) his Brno super 28 is great as well and real quiet but is scoped and would be like comparing apples to oranges. I am not sure if the extra 4" on his 28" slows the bullet down under the speed of sound or if the extra 12" of barrel act as a sound chamber. Next time I head over to his house and we shoot in the back yard range I will have to set up a Chrono.
Weather it is the weight of the rifle, the longer sight radius or that my 24" barrel slows the the bullet down to where a 22 lead bullets proform better, I do not know. But with modern powders and a centerfire rifle you should be able to match a load to your rifle that will be the most efficient as well as accurate. Or are these mutually exclusive?

BBF · « **Reply #12 on:** February 14, 2009, 08:59:38 AM »

I still don't see why the gas column would ever move slow enough not to push the bullet. They didn't teach us that in HS

mcwoodduck · « **Reply #13 on:** February 14, 2009, 10:13:52 AM »

The friction of the barrel over comes the speed of the projectile and the volume inside of the barrel behind the projectile exceeds the volume of the gas. Same reason why the little 22 Colibri rounds get stuck in my 24" CZ but not in my 16" H&R.

45-70.gov · « **Reply #14 on:** February 14, 2009, 10:28:54 AM »

this is my test
crony
cut
crony again

same box of shells

http://www.gboreloaded.com/forums/index.php/topic,160953.0.html

Graybeard · « **Reply #15 on:** February 14, 2009, 10:49:56 AM »

Actually the length of barrel needed to allow the powder to burn completely is grossly over estimated by most folks. It's less than a foot for almost anything that can be fired from the shoulder without damage to the shooter's body.

BUT the pressure continues to accelerate that bullet for considerably further which is why longer barrels get more velocity "to a point" and that point depends greatly on just how much powder is being burned and how much gas volume is produced.

kevinsmith5 · « **Reply #16 on:** February 17, 2009, 03:52:25 PM »

As a high school physics teacher I can tell you Greybeard is pretty much dead on.

jro45 · « **Reply #17 on:** February 18, 2009, 05:13:25 AM »

Quote from: BBF on February 14, 2009, 05:21:51 AM

I don't see any possible way for a bullet to slow down in a barrel unless it is as long as a naval gun and then only maybe. The bullet would have to be moving faster inside the barrel then then gas column behind it.
As long as there is pressure in the barrel the bullet will accelerate. If the peak pressure of a given firearm is reached at 8 " from the breech it isn't zero when the bullet is 22 or 24" down the tube.

The 10ga Is a shotgun the shot seened to slow down in it so thats why I cut it down to 28"
Its a lot better now.

Lloyd Smale · « **Reply #18 on:** February 19, 2009, 12:20:55 AM »

I agree with greybeard. Long barrels especially in a big bore like the 4570 are not needed. To me anything over 20 inch is just extra weight and bulk to carry around.

kevinsmith5 · « **Reply #19 on:** February 19, 2009, 01:48:42 PM »

I'm not sure that that constitutes agreeing with GreyBeard. When he said it helps up to a point I doubt he mad 20" in mind for the point.

Actually tests show the "big bores" are more likely to benefit form the extra length than the smaller calibers. Large cases hold more powder that produce larger volumes of gas. Also the surface area to mass ratio of a large bullet is lower, so there is less friction. My 32" barreled 45-70 generates 100-150 fps greater MV than the same loads out of a 22" barreled 45-70.

Autorim · « **Reply #20 on:** February 21, 2009, 01:49:28 AM »

Kevinsmith5,

I find your actual shooting results interesting. What powder are you using in the 45-70? It appears that 22 inches is not enough length in the 45-70 for optimum velocity. Personally, I would think that it would not require 32 inches though. Maybe the best length is between 22 and 32 inches. Has anyone tried other barrel lengths with the same load? Variables between barrels can cause velocity differentials too.

On the other hand, it really doesn't make much difference though. Hell, we're all going go shoot what we like and enjoy it anyway.

45-70.gov · « **Reply #21 on:** February 21, 2009, 02:12:22 PM »

http://www.gboreloaded.com/forums/index.php/topic,160953.0.html

this is my test

i also shot a 24 inch ss HnR ...different gun
it got a little bit more but don't have my notes handi

kevinsmith5 · « **Reply #22 on:** February 22, 2009, 01:28:35 PM »

I use Varget and H4198 the most (mostly Varget) when loading smokeless. I haven't done as much chrony work with the BP loads, mostly because I worry about powder residue having an adverse effect on my chrony.

sert01 · « **Reply #23 on:** February 23, 2009, 10:29:20 AM »

I've got a question i hope one of you'ns (Pa. speak for ya'll!!) could answer for me. I had a 45-70 custom built for me in 1985. It's a Siamese mauser action, Douglas 20"" barrel, with a full length Bastogne walnut mannlicher stock with two snaubels(sp?) carved on the front of the stock for my fingers to wrap around. The stock was custom made to fit me perfectly.I think it cost me over $200.00 in 1985 just for the walnut blank.The rifle weighs around ten pounds empty. I handload a Hornady 350 semi-jacketed roundnose,remington #9 1/2 large rifle primer,remington-peters case, with 50.5 grains of Imr 4198. Not too bad to shoot offhand but beats you up on the bench after about ten rounds or so. I always figured i was getting about 2,000-2100 fps with this load. Is that about right or can someone narrow it down a bit better? A good friend of mine built it for me while he was finishing up at the Pittsburgh Gunsmithing Institute. Total cost of the gun was about $750.00 back then .I would appreciate any ballistic info anyone can give me as i've never had a chance to chronograph it. Thanks, Sert01. ( By the way, the gun is a tackdriver at 100 yards with this load)

mcwoodduck · « **Reply #24 on:** February 24, 2009, 09:49:16 AM »

Sert01,
Go buy a chronograph.
look on any website like Midway or Midsouth that advertise here as well as Bass Pro or Cabelas that do not.
The cheap ones start around 100 bucks and go up from there.
But that is going to be the only way you are going to know what your rifle is doing with those loads.

DDZ · « **Reply #25 on:** February 24, 2009, 01:00:38 PM »

I did a bit of research on the subject and the issue with a longer barrel being more accurate than a shorter one is not true. Other then the fact, as others have stated here, is that a longer barrel is eaiser to hold steady because of the added weight forward, (better balance.) Untill at a certain length the rifle will be harder to hold steady because of to much weight forward. This is the reason you don't see trap shooters using 22 or 24 inch tubes. The quality of a barrel is much more a facter in accuracy than length. As for velocity Your higher pressure rounds like 7mm mag and 264 Win. will much more be affected by barrel length then say a big bore lower pressure round like 45/70. As a general rule of thumb a cartridge with a velocity of 1000 to 2000 fps will only change 5 fps per inch of barrel increase or decrease. A 3500 to 4000 fps round will be 40 fps per inch of barrel. You can reach a length of barrel when your bullet will start to slow down. This happens when the pressure in front of the bullet becomes the same or greater than the pressure behind the bullet. I relate it to about the same thing in an engine. You reach a peak firing pressure in your cylinder, and as the piston moves downward in the power stroke, area in the cylinder increases and pressure decreases. This pressure curve is the same thing in a rifle barrel. I guess that if you were shooting a slow burning powder in a short barrel the pressure may be still rising while the bullet exits the barrel. This is the reason longer barrels benifit from slow burning powders. As the bullet travels down say a 26 inch tube with a charge of slow burning powder, the peak pressure reaches a point with the bullet further down the barrel enabling the bullet to be driven at a faster velocity, because the expanding gases are still overcoming the increased area in the barrel.

Bama Bill · « **Reply #26 on:** March 24, 2009, 06:29:02 AM »

You guys are great ... all of you! This has been a great discussion and I have learned a lot on the subject of barrel length's effect on bullet performance. I still haven't gotten a chronograph ... but, I get roughly the same size groups at 100 yards with the 45-70 Ruger single-shot as I do with the Uberti 1874 replica ... however, the Ruger is scoped and the "Quigley" is iron peep sights. Both guns shoot 2" or smaller groups ... and, they keep getting better the more I practice (meaning that my ability is certainly a factor).

KAYR1 · « **Reply #27 on:** March 30, 2009, 03:59:42 AM »

I'd like to also mention that one should take into account the rifle's purpose. A 26 inch magnum in a treestand in close quarters is too long for me. On the other hand, it is no problem on the range or in open country. I have swithced to 22-24 inchers and shorter in treestands and blinds.

Also, a long barrel is a hindrance while still-hunting in thick cover. Just my 2c

DDZ · « **Reply #28 on:** March 30, 2009, 11:40:05 AM »

I agree, a long barrel hunting in thick stuff is a pain in the backside.
When I hunt in the brush I grab my Encore 45/70 with an 18 inch tube. Just love this gun for hunting in brush. In fact I like it so much it comes with me on most whitetail hunts.