I know there must be a point of diminished return in terms velocity related to length of barrel but what is it? Does it vary with caliber, powder, bullet type or weight? I am specifically interested in 6.5 caliber 130-140 gr VLD type bullets using H4831sc or comparable powder. I know the rule of thumb is 25fps per inch of barrel but also understand that at some point all of the propellant is completely burned & at some point the pressure would begin to fall off.Is that point within the practical range of barrel length,say 24" to 30" or would you continue to achieve an additional 25fps per inch for an additional 3"? 5"? 10"? As i said, i am now working on a 6.5 cal but would appreciate any general info that could be applied to other calibers if it it does in fact vary from cal to cal.
Barrel length as related to Velocity
- Thread starter Lucky
- Start date
From Chuckhawks:
Velocity loss (or gain)
It is worth noting that the velocity figures published in ammunition brochures and reloading manuals are sometimes taken in barrels different in length from those supplied on many rifles. I have seen various estimates of how much velocity is lost (or gained) when a barrel is not the same length as the test barrel in which a cartridge was chronographed. Here are some of them.
The 2001 Edition of the Shooter's Bible states, in the introduction to the Centerfire Rifle Ballistics section, "Barrel length affects velocity, and at various rates depending on the load. As a rule, figure 50 fps per inch of barrel, plus or minus, if your barrel is longer or shorter than 22 inches." However, they do not say what category of load to which this 50 fps average pertains.
Jack O'Connor wrote in The Rifle Book that, "The barrel shorter than standard has a velocity loss which averages about 25 foot-seconds for every inch cut off the barrel. Likewise, there is a velocity gain with a longer barrel." He went on to illustrate this using a .30-06 rifle shooting 180 grain bullets as an example, so his estimate was obviously for rifles in that general performance class.
Other authorities have tried to take into account the different velocity ranges within which modern cartridges operate. The Remington Catalog 2003 includes a "Centerfire Rifle Velocity Vs. Barrel Length" table that shows the following velocity changes for barrels shorter or longer than the test barrel length:
MV 2000-2500 fps, the approximate change in MV per 1" change in barrel length is 10 fps.
MV 2500-3000 fps, the approximate change in MV per 1" change in barrel length is 20 fps.
MV 3000-3500 fps, the approximate change in MV per 1" change in barrel length is 30 fps.
MV 3500-4000 fps, the approximate change in MV per 1" change in barrel length is 40 fps.
The 45th Edition of the Lyman Reloading Handbook also has a table showing Center Fire Rifle Velocity Vs. Barrel Length. Their figures apply to barrels between 20 and 26 inches in length and agree with the Remington figures. The Lyman table shows the following approximate velocity changes:
For rifles with muzzle velocities in the 1000-2000 fps range, the change in velocity for each 1" change in barrel length is 5 fps.
For rifles with muzzle velocities in the 2001-2500 fps range, the change in velocity for each 1" change in barrel length is 10 fps.
For rifles with muzzle velocities in the 2501-3000 fps range, the change in velocity for each 1" change in barrel length is 20 fps.
For rifles with muzzle velocities in the 3001-3500 fps range, the change in velocity for each 1" change in barrel length is 30 fps.
For rifles with muzzle velocities in the 3501-4000 fps range, the change in velocity for each 1" change in barrel length is 40 fps.
The 43rd edition of the Lyman reloading Handbook gave some concrete examples of velocity loss for specific calibers and loads. The Lyman technicians chronographed some high velocity cartridges in rifles with barrels ranging in length from 26 inches down to 22 inches with the following results:
The average loss for the .243 Win./100 grain bullet was 29 fps per inch.
The average loss for the .264 Win. Mag./140 grain bullet was 32 fps per inch.
The average loss for the .300 H&H Mag./220 grain bullet was 25 fps per inch.
For standard high intensity cartridges in the same test, the Lyman technicians chronographed the cartridges in barrel lengths ranging in length from 24 inches down to 20 inches with the following results:
The average loss for the .270 Win./130 grain bullet was 37 fps per inch.
The average loss for the .270 Win./150 grain bullet was 32 fps per inch.
The average loss for the .300 Sav./180 grain bullet was 17 fps per inch.
The average loss for the .30-06/180 grain bullet was 15 fps per inch.
The average loss for the .35 Rem./200 grain bullet was 11 fps per inch.
After a bunch of disclaimers, the Lyman people concluded, "The rule of thumb is that high speed, high pressure cartridges shed more speed in short barrels than do the low speed, large bore types." It's funny, but that is what I had suspected all along!
What I infer from the data above is that cartridges that are low to neutral overbore benefit less from additional barrel length. Those that are more overbore benefit more. So if you are going with a 6.5X47, you might not get as much velocity gain per inch as you would with a 6.5/284.
Velocity loss (or gain)
It is worth noting that the velocity figures published in ammunition brochures and reloading manuals are sometimes taken in barrels different in length from those supplied on many rifles. I have seen various estimates of how much velocity is lost (or gained) when a barrel is not the same length as the test barrel in which a cartridge was chronographed. Here are some of them.
The 2001 Edition of the Shooter's Bible states, in the introduction to the Centerfire Rifle Ballistics section, "Barrel length affects velocity, and at various rates depending on the load. As a rule, figure 50 fps per inch of barrel, plus or minus, if your barrel is longer or shorter than 22 inches." However, they do not say what category of load to which this 50 fps average pertains.
Jack O'Connor wrote in The Rifle Book that, "The barrel shorter than standard has a velocity loss which averages about 25 foot-seconds for every inch cut off the barrel. Likewise, there is a velocity gain with a longer barrel." He went on to illustrate this using a .30-06 rifle shooting 180 grain bullets as an example, so his estimate was obviously for rifles in that general performance class.
Other authorities have tried to take into account the different velocity ranges within which modern cartridges operate. The Remington Catalog 2003 includes a "Centerfire Rifle Velocity Vs. Barrel Length" table that shows the following velocity changes for barrels shorter or longer than the test barrel length:
MV 2000-2500 fps, the approximate change in MV per 1" change in barrel length is 10 fps.
MV 2500-3000 fps, the approximate change in MV per 1" change in barrel length is 20 fps.
MV 3000-3500 fps, the approximate change in MV per 1" change in barrel length is 30 fps.
MV 3500-4000 fps, the approximate change in MV per 1" change in barrel length is 40 fps.
The 45th Edition of the Lyman Reloading Handbook also has a table showing Center Fire Rifle Velocity Vs. Barrel Length. Their figures apply to barrels between 20 and 26 inches in length and agree with the Remington figures. The Lyman table shows the following approximate velocity changes:
For rifles with muzzle velocities in the 1000-2000 fps range, the change in velocity for each 1" change in barrel length is 5 fps.
For rifles with muzzle velocities in the 2001-2500 fps range, the change in velocity for each 1" change in barrel length is 10 fps.
For rifles with muzzle velocities in the 2501-3000 fps range, the change in velocity for each 1" change in barrel length is 20 fps.
For rifles with muzzle velocities in the 3001-3500 fps range, the change in velocity for each 1" change in barrel length is 30 fps.
For rifles with muzzle velocities in the 3501-4000 fps range, the change in velocity for each 1" change in barrel length is 40 fps.
The 43rd edition of the Lyman reloading Handbook gave some concrete examples of velocity loss for specific calibers and loads. The Lyman technicians chronographed some high velocity cartridges in rifles with barrels ranging in length from 26 inches down to 22 inches with the following results:
The average loss for the .243 Win./100 grain bullet was 29 fps per inch.
The average loss for the .264 Win. Mag./140 grain bullet was 32 fps per inch.
The average loss for the .300 H&H Mag./220 grain bullet was 25 fps per inch.
For standard high intensity cartridges in the same test, the Lyman technicians chronographed the cartridges in barrel lengths ranging in length from 24 inches down to 20 inches with the following results:
The average loss for the .270 Win./130 grain bullet was 37 fps per inch.
The average loss for the .270 Win./150 grain bullet was 32 fps per inch.
The average loss for the .300 Sav./180 grain bullet was 17 fps per inch.
The average loss for the .30-06/180 grain bullet was 15 fps per inch.
The average loss for the .35 Rem./200 grain bullet was 11 fps per inch.
After a bunch of disclaimers, the Lyman people concluded, "The rule of thumb is that high speed, high pressure cartridges shed more speed in short barrels than do the low speed, large bore types." It's funny, but that is what I had suspected all along!
What I infer from the data above is that cartridges that are low to neutral overbore benefit less from additional barrel length. Those that are more overbore benefit more. So if you are going with a 6.5X47, you might not get as much velocity gain per inch as you would with a 6.5/284.
Now for what its worth I have also heard there is a sweet spot in barrel length with harmonic's, don't know if anyone has heard this to be true???
DennisH
Life Time NRA member
I have heard a similiar statement!
I know a well know shooter who took a barrel and started off at 32", cut 2"of the barrel off per test until the barrel was down to 24".
His findings showed the shorter barrel was just as accurate as the longer one, but mostly, the shorter the barrel, the easier it was to find it's load and tune!
Everything he shoots now is 24"to 26". Most of mine are 26".
To back this up, a shooter in a match not long ago was shooting with a 24" barrel, 600 yds, and won the match with ease! Proved his point and test findings!
But some state not all the powder is burned before the bullet exits the shorter barrel!
I am starting to see many 223 being shot in F-TR competition. All are AR style with short barrels. Their tough to beat! In fact, I thought about putting a good scope on my DPMS 308 and trying it out in a match! I know how accurate it is out to 300 yds! Never tried 600!
XTR
F-TR obssessed shooting junkie
If you are shooting at 600 yards that will work, but back at the 1000 yard line I will take all the extra MV that I can get. I went from a 24 to a 30 this year on the rifle I use at 1000 and based on the dope from the match yesterday I needed about 3MOA less elevation to get there with basically the same load.
I've not seen anyone shoot a 223 at 1000, at least not in F-TR. The 223 doesn't give up much if anything from 600 in, but once you start getting further out the BCs just aren't there and the wind starts to eat your lunch.
There have been some recent discussions over on SH about barrel length and tactical comp guns. That place is chock full of guys who big fans of the "tactical" 20" barreled rifles so I was surprised to see the majority of people there running 24-26" tubes + brake in the 260/6.5-* competition rifles.
Ultimately it depends on your application. If you are shooting inside of 600 yards there probably isn't much point in a short action rifle in a non-magnum caliber running anything longer than 24, but if you are trying to stretch it out then I'd say that longer it better.
I've not seen anyone shoot a 223 at 1000, at least not in F-TR. The 223 doesn't give up much if anything from 600 in, but once you start getting further out the BCs just aren't there and the wind starts to eat your lunch.
There have been some recent discussions over on SH about barrel length and tactical comp guns. That place is chock full of guys who big fans of the "tactical" 20" barreled rifles so I was surprised to see the majority of people there running 24-26" tubes + brake in the 260/6.5-* competition rifles.
Ultimately it depends on your application. If you are shooting inside of 600 yards there probably isn't much point in a short action rifle in a non-magnum caliber running anything longer than 24, but if you are trying to stretch it out then I'd say that longer it better.
DennisH said:
I doubt he found that using any hunting cartridge.
W/resp to the speed and amount of powder to be burned, a barrel can be short enough to be a detriment to accuracy. This, due to excess muzzle pressures, causing ugly bullet release.
A 6PPC does so well in ~22 because it's burning a tiny amount of fast powder, at an efficient pressure, in a relatively large bore(for capacity)(same with a 30br).
But something like a 243Win in 22" would throw off a big portion of it's load as a fireball, slapping the base of any bullet in abstract directions.
jbpmidas
MR F-T/r
The only experience I have with this is between 2 of my rifles and 2 of a shoting buddy's rifles. In both cases, my barrel are shorter and in both cases I get higher velocity.
Rifle #1: Both rifles are Brux, 10 twist, .308, standard bore, .308 Bisley reamer. His barrel is 30", whereas mine is 28". My average velocity s 2660 and his is between 2610-2620. Sorry I don't remember his exact velocity. The only difference we can find is his throat is slightly longer, maybe .003.
Rifle #2: Both rifles are factory Savage .223's. Mine is an LRPV, 7 twist, 26". His is an F-T/r, 7 twist, 30". With 24.8 Varget under an 80 Amax, I get 2850, whereas he gets 2832. Again, his seating depth is slightly longer, but the difference is greater than on the Brux barrels.
I don't know what all that means, but there you go.
Rifle #1: Both rifles are Brux, 10 twist, .308, standard bore, .308 Bisley reamer. His barrel is 30", whereas mine is 28". My average velocity s 2660 and his is between 2610-2620. Sorry I don't remember his exact velocity. The only difference we can find is his throat is slightly longer, maybe .003.
Rifle #2: Both rifles are factory Savage .223's. Mine is an LRPV, 7 twist, 26". His is an F-T/r, 7 twist, 30". With 24.8 Varget under an 80 Amax, I get 2850, whereas he gets 2832. Again, his seating depth is slightly longer, but the difference is greater than on the Brux barrels.
I don't know what all that means, but there you go.
Less than 4†is the point of diminishing returns.
I have a stock M700 SPS, with a 26†bbl, in .308 that will hold 1 MOA to 800 and 900 yards when topped with 155gr SMK Palma bullet. But at 1000 yards it spreads out to 3 MOA. I need the extra 4†to keep the bullet above sonic at 1000yds.
The rifle went in for a rebarrel last week. Putting a new Kreiger 30†Palma barrel on it.
I have a stock M700 SPS, with a 26†bbl, in .308 that will hold 1 MOA to 800 and 900 yards when topped with 155gr SMK Palma bullet. But at 1000 yards it spreads out to 3 MOA. I need the extra 4†to keep the bullet above sonic at 1000yds.
The rifle went in for a rebarrel last week. Putting a new Kreiger 30†Palma barrel on it.
PALarson
High Power Competitor, XC and Long Range
I heard all of the above, I've been shooting competition for some 30 years, I can tell you that in no uncertain terms longer is better for long range shooting. I chrono everything and have found added velocity in longer lengths. Now powder selection is important so as to have the pressure rising the entire way down the tube.
PA Larson mid range - long range HM
PA Larson mid range - long range HM
But there are ALWAYS two sides of scale.
Shorter barrels are more accurate provided you burn up the powder with light bullets in them, or restrict yourself to flatbase bullets.
Longer barrels provide for better accuracy at distance, because there is room to push higher BC bullets to speed & still burn up the powder.
If you could wave a magic wand over competitive 6PPC ammo, causing the same bullets to be high in BC, the 6PPC with a ~21" barrel would blow everything away for accuracy at 1kyd, just as it has at 100yd.
As it stands, you could not pray to beat a 6PPC at 100yds with any 1kyd cartridge, regardless of barrel length.
Shorter barrels are more accurate provided you burn up the powder with light bullets in them, or restrict yourself to flatbase bullets.
Longer barrels provide for better accuracy at distance, because there is room to push higher BC bullets to speed & still burn up the powder.
If you could wave a magic wand over competitive 6PPC ammo, causing the same bullets to be high in BC, the 6PPC with a ~21" barrel would blow everything away for accuracy at 1kyd, just as it has at 100yd.
As it stands, you could not pray to beat a 6PPC at 100yds with any 1kyd cartridge, regardless of barrel length.
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.