Barrel Length Effects On Velocity & Accuracy

[Rem9671]

Does anyone know how much shorter and longer barrels affect accuracy on centerfire rifles?
Does anyone know about or where I can get a chart for min and max barrel lengths for different calibers.
Do anyone know if a longer or shorter barrel is more accurate or forgiving in relationship to a marksmans error?
Any other suggestions or considerations for barrel length on a custom rifle build?

 

[Sticks]

The quality of the barrel, and the load tuned for that barrel length (barrel harmonics) is the vast majority of the accuracy of the combination if you remove the shooter. That answers most of your questions.

Longer barrels will have a higher muzzle velocity than shorter with the same load fired. Higher muzzle velocity translates to less drop the farther down range, and longer distance before the projectile will go trans sonic.

Muzzle velocity will drop approximately 30 fps per inch down to 18", then it drops to IIRC 20fps per inch

Projectiles require a minimum spin rate for stability so (now I am speculating). A projectile fired from a 10" 1:8 twist barrel may not have the same stability as one fired from a 26" 1:8 due to having less time in the barrel imparting the spin energy to the projectile.

Barrel length max is as long as you want to deal with, never heard of one over 32".

Below 16" is an NFA item if a rifle, or make a pistol, then you can make the barrel .1" if you so desire....IN A PISTOL CONFIGURATION

Muzzle velocity is the forgiving part. You have more challenges firing a round plodding down range at 2450fps than one at 3000fps. Wind, Drop, trans sonic threshold... A properly tuned round fired from a 16" will have a given drop curve, and wind drift, just like one fired from a 26".

A target at 900y with my 6.5 Grendel with a 123gr ELDM MV of 2450, but I have to dial 11 mils at sea level, and have 357" of drop and 91" of wind drift (10mph)

Same target with my 6.5 PRC shooting the same 123 at 3020, I have to dial 6.7 mil with 215" of drop, and 64 inches of wind drift.

Just 1 mph less wind makes a difference of 10" with the Grendel, and 7" on the PRC. 880 yards is 22" less drop with the Grendel, 13" less drop on the PRC. Knowing your wind and exact distance to target is the difference between a hit and a miss. The faster the velocity, the more room for error in distance and wind calls.

So who is a better shot. The guy shooting a 123gr at 2450 and hitting 50 out of 60 targets at a match, or the guy shooting a 147gr at 3020 (better ballistic coefficient on the 147 = less drop and drift ~18%) and hitting 50 out of 60?

Barrel length and caliber is a lot dependent on what you want to do with it, or what your goals are. Prairie dog hunting with a 7 SAUM is fine, but really excessive and expensive unless you are trying to hit them at 1700y, Elk hunting with a 6.5 Grendel or .224 Vakyrie at 1000y is not a good choice unless you know you can make the wind calls, and make the shot placement for an ethical kill, not just simply hit the elk.

 

[mram10]

This link helps to understand the non linear relationship between length and speed

308 Winchester / 7.62x51mm NATO: Barrel Length versus Velocity (28″ to 16.5″)

308 Winchester / 7.62x51mm NATO: Barrel Length versus Velocity (28″ to 16.5″) Introduction Released by Winchester in 1952 (and adopted by NATO in 1954 as the 7.62x51mm NATO), the 308 Wi…

rifleshooter.com

Regarding your Accuracy question, it is barrel dependent and depends on harmonics as stated above.
Best of luck

 

[Greg Langelius *]

If the key factor was just length, that could be contradicted by the simple fact that harmonic tuning weights can moderate harmonics adequately enough to bring harmonics and barrel transit time into harmony without actually altering bore/barrel length or barrel transit time.

It's a tradeoff. Both are critical, because natural vibration frequencies are also dependent on factors like the barrel's polar moment of inertia; which depends on mass distribution along the barrel's length.

Bear in mind that barrels can be vibrating at different frequencies at the same time. Those frequencies are usually multiples of a single main frequency. Slow motion photography of a vibrating guitar string is a good demonstration of this factor. This factor can have some interesting effects upon accuracy nodes.

Greg

 

[spife7980]

Most velocity is gained in the first few inches of barrel

In this 308 at 16" its going 2,500 fps, at 26" its going 2,800. But at only 6" its already going 2,000 fps.

Accuracy can be completely independent of length and velocity. Accuracy is more related to how well your equipment is machined true and how straight your ammo is and how well its loaded to match the barrels preference. The actual amount of time it spends in the barrel doesnt really matter beyond wanting to achieve a certain relative velocity.

 

[Rem9671]

The quality of the barrel, and the load tuned for that barrel length (barrel harmonics) is the vast majority of the accuracy of the combination if you remove the shooter. That answers most of your questions.

Longer barrels will have a higher muzzle velocity than shorter with the same load fired. Higher muzzle velocity translates to less drop the farther down range, and longer distance before the projectile will go trans sonic.

Muzzle velocity will drop approximately 30 fps per inch down to 18", then it drops to IIRC 20fps per inch

Projectiles require a minimum spin rate for stability so (now I am speculating). A projectile fired from a 10" 1:8 twist barrel may not have the same stability as one fired from a 26" 1:8 due to having less time in the barrel imparting the spin energy to the projectile.

Barrel length max is as long as you want to deal with, never heard of one over 32".

Below 16" is an NFA item if a rifle, or make a pistol, then you can make the barrel .1" if you so desire....IN A PISTOL CONFIGURATION

Muzzle velocity is the forgiving part. You have more challenges firing a round plodding down range at 2450fps than one at 3000fps. Wind, Drop, trans sonic threshold... A properly tuned round fired from a 16" will have a given drop curve, and wind drift, just like one fired from a 26"

The quality of the barrel, and the load tuned for that barrel length (barrel harmonics) is the vast majority of the accuracy of the combination if you remove the shooter. That answers most of your questions.

Longer barrels will have a higher muzzle velocity than shorter with the same load fired. Higher muzzle velocity translates to less drop the farther down range, and longer distance before the projectile will go trans sonic.

Muzzle velocity will drop approximately 30 fps per inch down to 18", then it drops to IIRC 20fps per inch

Projectiles require a minimum spin rate for stability so (now I am speculating). A projectile fired from a 10" 1:8 twist barrel may not have the same stability as one fired from a 26" 1:8 due to having less time in the barrel imparting the spin energy to the projectile.

Barrel length max is as long as you want to deal with, never heard of one over 32".

Below 16" is an NFA item if a rifle, or make a pistol, then you can make the barrel .1" if you so desire....IN A PISTOL CONFIGURATION

Muzzle velocity is the forgiving part. You have more challenges firing a round plodding down range at 2450fps than one at 3000fps. Wind, Drop, trans sonic threshold... A properly tuned round fired from a 16" will have a given drop curve, and wind drift, just like one fired from a 26".

A target at 900y with my 6.5 Grendel with a 123gr ELDM MV of 2450, but I have to dial 11 mils at sea level, and have 357" of drop and 91" of wind drift (10mph)

Same target with my 6.5 PRC shooting the same 123 at 3020, I have to dial 6.7 mil with 215" of drop, and 64 inches of wind drift.

Just 1 mph less wind makes a difference of 10" with the Grendel, and 7" on the PRC. 880 yards is 22" less drop with the Grendel, 13" less drop on the PRC. Knowing your wind and exact distance to target is the difference between a hit and a miss. The faster the velocity, the more room for error in distance and wind calls.

So who is a better shot. The guy shooting a 123gr at 2450 and hitting 50 out of 60 targets at a match, or the guy shooting a 147gr at 3020 (better ballistic coefficient on the 147 = less drop and drift ~18%) and hitting 50 out of 60?

Barrel length and caliber is a lot dependent on what you want to do with it, or what your goals are. Prairie dog hunting with a 7 SAUM is fine, but really excessive and expensive unless you are trying to hit them at 1700y, Elk hunting with a 6.5 Grendel or .224 Vakyrie at 1000y is not a good choice unless you know you can make the wind calls, and make the shot placement for an ethical kill, not just simply hit the elk.

Does anyone know how much shorter and longer barrels affect accuracy on centerfire rifles?
Does anyone know about or where I can get a chart for min and max barrel lengths for different calibers.
Do anyone know if a longer or shorter barrel is more accurate or forgiving in relationship to a marksmans error?
Any other suggestions or considerations for barrel length on a custom rifle build?

Does anyone know how much shorter and longer barrels affect accuracy on centerfire rifles?
Does anyone know about or where I can get a chart for min and max barrel lengths for different calibers.
Do anyone know if a longer or shorter barrel is more accurate or forgiving in relationship to a marksmans error?
Any other suggestions or considerations for barrel length on a custom rifle build?

The quality of the barrel, and the load tuned for that barrel length (barrel harmonics) is the vast majority of the accuracy of the combination if you remove the shooter. That answers most of your questions.

Longer barrels will have a higher muzzle velocity than shorter with the same load fired. Higher muzzle velocity translates to less drop the farther down range, and longer distance before the projectile will go trans sonic.

Muzzle velocity will drop approximately 30 fps per inch down to 18", then it drops to IIRC 20fps per inch

Projectiles require a minimum spin rate for stability so (now I am speculating). A projectile fired from a 10" 1:8 twist barrel may not have the same stability as one fired from a 26" 1:8 due to having less time in the barrel imparting the spin energy to the projectile.

Barrel length max is as long as you want to deal with, never heard of one over 32".

Below 16" is an NFA item if a rifle, or make a pistol, then you can make the barrel .1" if you so desire....IN A PISTOL CONFIGURATION

Muzzle velocity is the forgiving part. You have more challenges firing a round plodding down range at 2450fps than one at 3000fps. Wind, Drop, trans sonic threshold... A properly tuned round fired from a 16" will have a given drop curve, and wind drift, just like one fired from a 26".

A target at 900y with my 6.5 Grendel with a 123gr ELDM MV of 2450, but I have to dial 11 mils at sea level, and have 357" of drop and 91" of wind drift (10mph)

Same target with my 6.5 PRC shooting the same 123 at 3020, I have to dial 6.7 mil with 215" of drop, and 64 inches of wind drift.

Just 1 mph less wind makes a difference of 10" with the Grendel, and 7" on the PRC. 880 yards is 22" less drop with the Grendel, 13" less drop on the PRC. Knowing your wind and exact distance to target is the difference between a hit and a miss. The faster the velocity, the more room for error in distance and wind calls.

So who is a better shot. The guy shooting a 123gr at 2450 and hitting 50 out of 60 targets at a match, or the guy shooting a 147gr at 3020 (better ballistic coefficient on the 147 = less drop and drift ~18%) and hitting 50 out of 60?

Barrel length and caliber is a lot dependent on what you want to do with it, or what your goals are. Prairie dog hunting with a 7 SAUM is fine, but really excessive and expensive unless you are trying to hit them at 1700y, Elk hunting with a 6.5 Grendel or .224 Vakyrie at 1000y is not a good choice unless you know you can make the wind calls, and make the shot placement for an ethical kill, not just simply hit the elk.

A target at 900y with my 6.5 Grendel with a 123gr ELDM MV of 2450, but I have to dial 11 mils at sea level, and have 357" of drop and 91" of wind drift (10mph)

Same target with my 6.5 PRC shooting the same 123 at 3020, I have to dial 6.7 mil with 215" of drop, and 64 inches of wind drift.

Just 1 mph less wind makes a difference of 10" with the Grendel, and 7" on the PRC. 880 yards is 22" less drop with the Grendel, 13" less drop on the PRC. Knowing your wind and exact distance to target is the difference between a hit and a miss. The faster the velocity, the more room for error in distance and wind calls.

So who is a better shot. The guy shooting a 123gr at 2450 and hitting 50 out of 60 targets at a match, or the guy shooting a 147gr at 3020 (better ballistic coefficient on the 147 = less drop and drift ~18%) and hitting 50 out of 60?

Barrel length and caliber is a lot dependent on what you want to do with it, or what your goals are. Prairie dog hunting with a 7 SAUM is fine, but really excessive and expensive unless you are trying to hit them at 1700y, Elk hunting with a 6.5 Grendel or .224 Vakyrie at 1000y is not a good choice unless you know you can make the wind calls, and make the shot placement for an ethical kill, not just simply hit the elk.

The quality of the barrel, and the load tuned for that barrel length (barrel harmonics) is the vast majority of the accuracy of the combination if you remove the shooter. That answers most of your questions.

Longer barrels will have a higher muzzle velocity than shorter with the same load fired. Higher muzzle velocity translates to less drop the farther down range, and longer distance before the projectile will go trans sonic.

Muzzle velocity will drop approximately 30 fps per inch down to 18", then it drops to IIRC 20fps per inch

Projectiles require a minimum spin rate for stability so (now I am speculating). A projectile fired from a 10" 1:8 twist barrel may not have the same stability as one fired from a 26" 1:8 due to having less time in the barrel imparting the spin energy to the projectile.

Barrel length max is as long as you want to deal with, never heard of one over 32".

Below 16" is an NFA item if a rifle, or make a pistol, then you can make the barrel .1" if you so desire....IN A PISTOL CONFIGURATION

Muzzle velocity is the forgiving part. You have more challenges firing a round plodding down range at 2450fps than one at 3000fps. Wind, Drop, trans sonic threshold... A properly tuned round fired from a 16" will have a given drop curve, and wind drift, just like one fired from a 26".

A target at 900y with my 6.5 Grendel with a 123gr ELDM MV of 2450, but I have to dial 11 mils at sea level, and have 357" of drop and 91" of wind drift (10mph)

Same target with my 6.5 PRC shooting the same 123 at 3020, I have to dial 6.7 mil with 215" of drop, and 64 inches of wind drift.

Just 1 mph less wind makes a difference of 10" with the Grendel, and 7" on the PRC. 880 yards is 22" less drop with the Grendel, 13" less drop on the PRC. Knowing your wind and exact distance to target is the difference between a hit and a miss. The faster the velocity, the more room for error in distance and wind calls.

So who is a better shot. The guy shooting a 123gr at 2450 and hitting 50 out of 60 targets at a match, or the guy shooting a 147gr at 3020 (better ballistic coefficient on the 147 = less drop and drift ~18%) and hitting 50 out of 60?

Barrel length and caliber is a lot dependent on what you want to do with it, or what your goals are. Prairie dog hunting with a 7 SAUM is fine, but really excessive and expensive unless you are trying to hit them at 1700y, Elk hunting with a 6.5 Grendel or .224 Vakyrie at 1000y is not a good choice unless you know you can make the wind calls, and make the shot placement for an ethical kill, not just simply hit the elk.

 

[GunnyUSMC]

I have been trying to get my head wrapped around this question for a while now. I have read many articles and there seems to be some agreements and some contradictions. In reading the "Accuracy and Precision for Long Range Shooting" by Bryan Litz, he states in Chapter 6 that muzzle velocity increases with barrel length. I believed that too and to add to it, I understood that the 6.5 creedmore was developed around a 24" barrel. I am shooting a Wilson Combat AR-10 chambered in 6.5 creedmore with a 22" barrel. I was struggling to get the groups i hoped for so i decided to freshen it up by installing a new barrel from Wilson Combat that is 24" long. To make a long story short, my muzzle velocity using the same exact load DROPPED by about 50fps and my groups were not impressive.

In reading multiple articles on this topic, this is a common thing depending on caliber. However, i never expected to lose MV going from a 22" to 24" barrel with the exact same load. My muzzle velocity with the 22" barrel was appx 1760 average and it dropped to an average of about 2705. My load consisted of Lapua brass, Lapua Scenar L 136gr, and Vihtavouri N550 powder.

I recently reduced my load to get a velocity closer to 2640 just to see if this lower velocity was a better fit for my rifle and the results are still not what I was hoping for. I am now going to increase my loads to get upwards of 2750 to see if that works any better. The problem i run into here is that with those kinds of loads, the AR-10 action is hard on my brass and they come out piping HOT, something i am really not comfortable with.

Other things i have heard is that if you go with a longer barrel, make sure it is a bigger (diameter) barrel because you can experience a whipping action from the smaller barrel. not sure if there is any truth to this, just something i read.

After all my frustration in trying to get a consistent sub-MOA out of my WC AR-10, I finally decided to invest in a custom bolt gun with a Impact Precision action, Bartlein 24" barrel chambered in 6.5 creedmore and Foundation Genesis II stock. Cant wait to compare performance.

 

[Rio Precision Gunworks]

I have been trying to get my head wrapped around this question for a while now. I have read many articles and there seems to be some agreements and some contradictions. In reading the "Accuracy and Precision for Long Range Shooting" by Bryan Litz, he states in Chapter 6 that muzzle velocity increases with barrel length. I believed that too and to add to it, I understood that the 6.5 creedmore was developed around a 24" barrel. I am shooting a Wilson Combat AR-10 chambered in 6.5 creedmore with a 22" barrel. I was struggling to get the groups i hoped for so i decided to freshen it up by installing a new barrel from Wilson Combat that is 24" long. To make a long story short, my muzzle velocity using the same exact load DROPPED by about 50fps and my groups were not impressive.

In reading multiple articles on this topic, this is a common thing depending on caliber. However, i never expected to lose MV going from a 22" to 24" barrel with the exact same load. My muzzle velocity with the 22" barrel was appx 1760 average and it dropped to an average of about 2705. My load consisted of Lapua brass, Lapua Scenar L 136gr, and Vihtavouri N550 powder.

I recently reduced my load to get a velocity closer to 2640 just to see if this lower velocity was a better fit for my rifle and the results are still not what I was hoping for. I am now going to increase my loads to get upwards of 2750 to see if that works any better. The problem i run into here is that with those kinds of loads, the AR-10 action is hard on my brass and they come out piping HOT, something i am really not comfortable with.

Other things i have heard is that if you go with a longer barrel, make sure it is a bigger (diameter) barrel because you can experience a whipping action from the smaller barrel. not sure if there is any truth to this, just something i read.

After all my frustration in trying to get a consistent sub-MOA out of my WC AR-10, I finally decided to invest in a custom bolt gun with a Impact Precision action, Bartlein 24" barrel chambered in 6.5 creedmore and Foundation Genesis II stock. Cant wait to compare performance.

Barrel to barrel velocity is going to be different. You may have a smaller or larger bore size in the new barrel.

Also, if the barrel is brand new, it will speed up somewhere between 50-200rnds.

So, if you’re comparing a used and sped up 24” to a new 22”, the slower speed is not surprising. If they are both sped up already, then it’s going to be one or several of the other minutia that dictates a barrel’s speed.

 

[Rio Precision Gunworks]

I have been trying to get my head wrapped around this question for a while now. I have read many articles and there seems to be some agreements and some contradictions. In reading the "Accuracy and Precision for Long Range Shooting" by Bryan Litz, he states in Chapter 6 that muzzle velocity increases with barrel length. I believed that too and to add to it, I understood that the 6.5 creedmore was developed around a 24" barrel. I am shooting a Wilson Combat AR-10 chambered in 6.5 creedmore with a 22" barrel. I was struggling to get the groups i hoped for so i decided to freshen it up by installing a new barrel from Wilson Combat that is 24" long. To make a long story short, my muzzle velocity using the same exact load DROPPED by about 50fps and my groups were not impressive.

In reading multiple articles on this topic, this is a common thing depending on caliber. However, i never expected to lose MV going from a 22" to 24" barrel with the exact same load. My muzzle velocity with the 22" barrel was appx 1760 average and it dropped to an average of about 2705. My load consisted of Lapua brass, Lapua Scenar L 136gr, and Vihtavouri N550 powder.

I recently reduced my load to get a velocity closer to 2640 just to see if this lower velocity was a better fit for my rifle and the results are still not what I was hoping for. I am now going to increase my loads to get upwards of 2750 to see if that works any better. The problem i run into here is that with those kinds of loads, the AR-10 action is hard on my brass and they come out piping HOT, something i am really not comfortable with.

Other things i have heard is that if you go with a longer barrel, make sure it is a bigger (diameter) barrel because you can experience a whipping action from the smaller barrel. not sure if there is any truth to this, just something i read.

After all my frustration in trying to get a consistent sub-MOA out of my WC AR-10, I finally decided to invest in a custom bolt gun with a Impact Precision action, Bartlein 24" barrel chambered in 6.5 creedmore and Foundation Genesis II stock. Cant wait to compare performance.

You also didn’t mention seating depth, just charge weight in an attempt to get your ammo shooting well.

If your velocities are consistent with your charge weights, work on the seating depth and you’ll see the groups shrink.

 

[GunnyUSMC]

For the AR-10 i did explore getting my bullet closer to the lands/grooves. While there may have been some improvement, the reality is that i am limited by my magazine length without manually feeding each round, which is not feasible unless shooting in an F-Class match. I eventually decided not to invest anymore time in that effort but will reconsider as i work up new loads for my new Bolt-Gun build.

 

[Rio Precision Gunworks]

For the AR-10 i did explore getting my bullet closer to the lands/grooves. While there may have been some improvement, the reality is that i am limited by my magazine length without manually feeding each round, which is not feasible unless shooting in an F-Class match. I eventually decided not to invest anymore time in that effort but will reconsider as i work up new loads for my new Bolt-Gun build.

You can keep moving away from the lands. Start at max mag length and work back. As long as the rifle is g2g, you’ll find several spots where the rifle shoots well, even with large amounts of jump

 

[GunnyUSMC]

Thanks for the advice... I started doing just that and so far, I am seeing some improvement. With a few more load tests, hopefully I will finally find that magic combination that gets me where I want to be.