Are there any general rules about how many FPS you gain/loose for every inch of barrel for standard cartridges? Magnums?

It depends on the specific expansion ratio of the cartridge and what the load is. Bullet weight, powder burning speed, etc. The smaller bore/large capacity cases will lose a lot more speed than the large bore/ large capacity cases.
Here's a chart for the 223:

Remington publishes it as a component of muzzle velocity with the following results:
Muz Vel Range Chg per inch
2000-2500 10
2500-3000 20
3000-3500 30
3500-4000 40
Where the change is in feet per second and the base barrel length is 24". I have read extensive test cases in Rifleman in the past where like changes were observed when cutting actual barrels and using same load. These figures are from 2003 and I would assume to be pretty accurate. I have always thought barrel length was not a SIGNIFICIENT factor in velocity and have made my barrels a length that looked and felt good. Only case in my estimation where the longer length barrels are necessary are with the use of iron sights which with my old eyes are mostly of little use at any distance over about 25 yards.

Not sure what your looking for.

A common misconception is that long barrels are faster than short barrels. This is true in a given barrel, but very untrue in two different barrels.

You could chamber two different barrels for the same cartridge, cut them at different lengths, and the shorter be the faster with a given load. I see this all of the time.

The reason I say this is because I often hear folks say "I'm going to buy X brand because they have 26" barrels and Y brand only has 22" bbls, X will be faster." Not always true, the chrony breaks many myths

In a given custom bbl, it will be faster at longer lengths. You can get approximations, but a chrony will be the truth teller in how much velocity you'll lose when you shorten....

Good Luck

Reloader

Depends. A 7 mag looses a ton more than a .308 .

Here is a little test from our friends here at Accurate Reloading.
http://www.accuratereloading.com/223sb.html

steve4102,
I suppose I'm pretty dense but I fail to see the point of the experiment. Exactly WHAT was trying to be shown? Or what point was trying to be made?

quote:

Originally posted by zimbabwe:
steve4102,
I suppose I'm pretty dense but I fail to see the point of the experiment. Exactly WHAT was trying to be shown? Or what point was trying to be made?

Saeed just took a 223 with a 22 inch barrel and with three different loads measured the velocity.
He then cut off one inch of barrel and measured the velocity again with the same loads.
He repeated this until he got down to a 10" barrel length.

I fully understand WHAT he did ,I fail to understand WHY he did it.

quote:

Originally posted by zimbabwe:
I fully understand WHAT he did ,I fail to understand WHY he did it.

Pursuit of knowledge

I Have to agree that you never can tell.
You might look at it this way.
If you cut a particular barrel, you will likly loose velocity.
If you look at 2 seperate barrels you best bet if velocity is what you seek , the longer is more likly to give it.
But there are many variables. A tight chamber increases velocity, as smoother bore will give you less friction and increase velocity.
And there are probably other factors as well.
I have 2 rifles chaberd for the Roberts.
One is a 20 inch Ruger while the other is a 24 inch custom.
I get 3100 with the ruger shooting 100 grain tsx bullets but my custom is at 3000 with the same load.
I would not be suprised if other loads give the opisate results.
...tj3006

I would think that if the question is 'what effect barrel length has on velocity' you would start with a SINGLE bullet and load and a long barrel and start cutting and shooting and chronographing. This would then answer the question. When you introduce another powder you have now introduced a NEW question just as you do when you change the powder charge. In these questions you have knowledge but it really has no meaning past the SINGLE set of variables.

I had no idea it varied so much barrel to barrel to load.

quote:

Originally posted by zimbabwe:
I would think that if the question is 'what effect barrel length has on velocity' you would start with a SINGLE bullet and load and a long barrel and start cutting and shooting and chronographing. This would then answer the question.

You really are being dense. That's exactly what he did. He just wanted to see what the result would be with different powders.
----------------------------------------------
"Serious rifles have two barrels, everything else just burns gunpowder."

I suppose I am dense as I thought it was only logical that ANY bullet loses velocity when shot from a shorter than optimum barrel length. It has always been my understanding that a powder burn rate determines the pressure curve to length of a barrel and therefore there is an optimum length where no more increase in pressure is created. I know that this is a simplification before you object. I also know that ANY decrease in this length results in a decrease in velocity in all cases. I have NEVER seen a test where velocity INCREASED under these circumstances. I also know that this point and the amount of loss will vary anytime ANYTHING is changed in the equation be it powder,amount of powder,barrel,bullet etc. Since it does vary from the introduction of these variables there is little you can do but use a rule of thumb to GUESS at what the result will be with a given barrel. Guess I'm just not that curious about what is to me such a logical conclusion. I only need a rule of thumb and the Remington data provides that for me.

quote:

Originally posted by zimbabwe:
I suppose I am dense as I thought it was only logical that ANY bullet loses velocity when shot from a shorter than optimum barrel length. It has always been my understanding that a powder burn rate determines the pressure curve to length of a barrel and therefore there is an optimum length where no more increase in pressure is created. I know that this is a simplification before you object. I also know that ANY decrease in this length results in a decrease in velocity in all cases. I have NEVER seen a test where velocity INCREASED under these circumstances. I also know that this point and the amount of loss will vary anytime ANYTHING is changed in the equation be it powder,amount of powder,barrel,bullet etc. Since it does vary from the introduction of these variables there is little you can do but use a rule of thumb to GUESS at what the result will be with a given barrel. Guess I'm just not that curious about what is to me such a logical conclusion. I only need a rule of thumb and the Remington data provides that for me.

---------------------------------------------
"Serious rifles have two barrels, everything else just burns gunpowder."

quote:

I had no idea it varied so much barrel to barrel to load.

I wouldn't have thought there would've been as much variation as well, but enough rifles behind a chrony taught me to never guesstimate velocities of anything until the chrony told the truth.

Have a Good One,

Reloader

Well I don't have a Chrony, I have an Oehler 35P and an Oehler M61. I have been chronographing since '75 and have choronographed lots of different rifles, many of the same caliber. I have only found one instance of a shorter barrel giving higher velocities than a longer barrel of the same cartridge with the same load. This was with a 22" M70 6.5x55 when compared to a 24" M36. On closer examination the reason for it was the M70 had a groove diameter of .264 and the M96 was .266. Thus the M70 had a much tighter bore and was faster (only 15 fps) with the same load (Hornady Light Magnum).

Invariably longer barrels shoot faster with a given load than short barrels do.

I have shortened numerous barrels over the years and when talking velocity loss there is no hard and fast figures. It does depend on the cartridge, the load and the length of barrel you started with as mentioned in a previous post. In the .223 test posted there's really not a lot of velocity loss from a 22" barrel to a 20" barrel (still more than I want to loose for the sake of 2"). However, if we take a look at the loss from a 26" barreled .223 down to a 20" barrel we would find it can be substantial.

In the case of the 30-06 for example; If we are shooting heavy bullets (180-200 gr) with slow burning powders the loss from a 24/26" barrel down to a 18/20" barrel is substantial. It can be as much as 200+ fps. Ever shoot a short barreled rifle and notice all the excessive muzzle blast? That excessive muzzle blast is the wasted energy that is not pushing the bullet faster. If you're hunting deer in the thick stuff and the longest shot may be 150-200 yards across a clearing then the velocity loss doesn't mean much from a practical point of view. However, if you are hunting elk where you may shoot at 300+ yards then 200+ fps is a lot to give up for the sake of a few inches of barrel and a percieved degree of "handiness".

Larry Gibson

I believe the original question is 'are there any GENERAL rules' for loss of velocity with reduction in barrel length. I don't think any reasonable person would question the fact that this reduction takes place. As pertains to the AR studies in barrel shortening one fact does appear that further reinforces Remington's general rule. If you will look at the base load velocities with each powder and then compare the velocities at the start length and the velocities at the 10" length you will find the loss to be almost the same across the 3 powders which would stand to reinforce the Remington 'GENERAL' data. Just an interesting observation.

quote:

Originally posted by zimbabwe:
Remington publishes it as a component of muzzle velocity with the following results:
Muz Vel Range Chg per inch
2000-2500 10
2500-3000 20
3000-3500 30
3500-4000 40
Where the change is in feet per second and the base barrel length is 24". I have read extensive test cases in Rifleman in the past where like changes were observed when cutting actual barrels and using same load. These figures are from 2003 and I would assume to be pretty accurate. I have always thought barrel length was not a SIGNIFICIENT factor in velocity and have made my barrels a length that looked and felt good. Only case in my estimation where the longer length barrels are necessary are with the use of iron sights which with my old eyes are mostly of little use at any distance over about 25 yards.

Yes, this is answers the question - and seems to indicate to me that despite the variablity of different loads ect, the difference between a 24" and 26" barrel at mid velocities isn't going to be a big deal, IMO.

quote:

Originally posted by Wayfaring Stranger:
Are there any general rules about how many FPS you gain/loose for every inch of barrel for standard cartridges? Magnums?

There are rules and there is reality.

My two 243s were much more affected by shortening than the rules stated.

my Steyr SBS barrels are very fast and dont seem to suffer from shorter tubes very much.
GM308M 168's shoot at 2550 FPS from my 20" tactical.
heres an interesting article...
Barrel length, accuracy and ballistics

It is worth mentioning that a longer barrel is not inherently more accurate than a short barrel. Intrinsic accuracy is a matter of quality, not length. However, a longer barrel is generally better in terms of practical accuracy because a longer and therefore heavier barrel (within reason) is easier to hold relatively steady from unsupported positions; thus it is easier to shoot a long barreled rifle accurately.

The length of the rifle barrel has a direct influence on the velocity obtained from the cartridge for which it is chambered. Ballistically, longer is usually better. But for carrying, handling, and maneuvering in close quarters (like thick brush) shorter is usually better. So some sort of compromise must be reached.

Very long 27-30 inch barrels are seldom seen these days on repeating hunting rifles, although they are still occasionally found on single shot hunting rifles and target rifles. The longest barrels usually seen on hunting rifles today are 26 inches in length.

26 inch barrels are usually found on rifles chambered for high velocity magnum cartridges. A long barrel is required to burn the large amounts of slow burning powder used in this type of cartridge. Unfortunately, most repeating rifles with 26 inch barrels balance too far forward--they are muzzle heavy, and slow to swing. The long barrel seems to hang up on every limb and outcropping of rock in the area, and a hunting rifle so equipped can be very awkward carry in steep terrain.

For this reason, many magnum rifles now come with 24 inch barrels, which sacrifice some of the magnum's velocity. 24 inches is about the minimum barrel length practical for most magnum cartridges. Cut a magnum's barrel down to 22 inches and the muzzle blast and flash become intimidating. Also, magnum cartridges like the .264 Win. or 7mm Rem. lose so much velocity in a 22 inch barrel that they show little ballistic advantage over standard calibers like the .270 or .280.

The typical barrel length for a repeating hunting rifle chambered for standard high intensity cartridges, like the .243, .270, .308, or .30-06, is 22-24 inches, with 22 inches being the more common length today. This is a useful all-around barrel length for these cartridges. Such cartridges will attain higher velocity in a 24 inch barrel, but the velocity loss in a 22 inch barrel is not extreme, and a rifle with a barrel of this length usually balances and swings well.

Cartridges with smaller cases that burn less powder, like all .22 Rimfire cartridges, the .250-300, .30-30, .300 Sav., and .35 Rem., do well in 20-22 inch barrels. The very popular carbine versions of classic lever action rifles like the Winchester 94 and Marlin 336 usually come with 20 inch barrels. These short rifles ride well in a saddle scabbard, are easy to carry in rugged terrain, and handle fast in close quarters. Because they are light rifles, they balance well with a 20 inch barrel. Muzzle blast from these cartridges in a 20 inch barrel is less severe than from the larger high intensity cartridges in a 22 inch barrel.

Combine a high intensity cartridge with a 20 inch barrel, however, and the velocity drops noticeably while the blast becomes annoying. Still, a lightweight rifle with a 20 inch barrel, chambered for short action cartridges like the .243, .260 Rem, or 7mm-08, makes a very effective mountain rifle. These cartridges retain enough velocity in a 20 inch barrel to handle the occasional long shot mountain hunting presents, and the stubby barrel is less likely than longer tubes to get hung up on overhanging ledges, rocky outcroppings, and so forth.

To my mind it is hard to justify barrels much shorter than 20 inches for any purpose. I have owned rifles with 18.5 inch barrels, and in every case I wished that they had come with a 20 inch barrel. Very short barrels of standard contour (not bull barrels) tend to make the rifle muzzle light and unsteady to hold and swing. I like a rifle to balance between my hands, not toward the butt. Even .22 rimfire rifles balance better with 20-22 inch barrels, although in this instance the longer barrel has no ballistic advantage, since the .22 LR cartridge burns all of of its powder in about 16 inches. Very short barrels also increase the muzzle blast from high intensity cartridges to very annoying levels, and the velocity loss is excessive.

quote:

I fully understand WHAT he did ,I fail to understand WHY he did it.

I think that I can remember a similar thing in a Guns and Ammo in the 1970s. Basically it shows that the easiest way to achieve maximum velocities is not to add powder but to lengthen the barrel!

Indeed for every inch of barrel over 20" I think that in, say .270, you can drop probably one full quarter of a grain yet still achieve the same velocity.

What is most revealing is the difference between a 22" and a 24" and a 26" barrel. I really can never understand why so many makers fit 22" barrels on "semi-magnum" rifles.

I shot my first deer in 1989 with a .270 Churchill with a 22" barrel. using Winchester 130 grain factory. The muzzle blast was very unpleasant. It served only to put me off the .270 Winchester for over eighteen years!

Yet for some I used a .280 Ross M-1905 sporting rifle with I think either a 26" or 28" barrel and despite achieving the nearly same velocity at the muzzle as others were in there 22" barrel 7mm Remington Magnum performance the rifle was very pleasant to shoot.

There is a useful project here. Start with a 26" barrel and four handloads, say 62 grains of X, 61.5 grains of X, 61 grains of X and 60.5 grains of X and keep shortening the barrel by an inch.

There WILL come a point where in the 26" barrel that the 60.5 grains of X will have been shooting a higher velocity that the barrel, now shortened, with 62 grains of X.

i would think that there is a point at which a longer barrel would actually reduce velocity. if all the powder has burned (ie fuel source) and the bullet still has inches of barrel to go (ie friction and drag) wouldnt that slow the projectile?

i dont know...

odd enough as that is i have a ruger 308 w/ a 16.5" barrel that is very quiet. when i killed a deer with it at camp thanksgiving some people hadnt even heard me shoot and those that did hear the shot stated it was muffled and sounded like a short pop.
i was using a 165 BTSP over 41.5gr H4895.

quote:

i would think that there is a point at which a longer barrel would actually reduce velocity

Yes! In fact for short range pest shooting with a .22 Rimfire there is no need to buy a silencer. Just shoot the CCI "CB Long" cartrdges and you'll have a whisper quiet rifle, as the barrel itself acts as the expansion chamber as all the powder is burnt out within the first ten inches.

It's the reason that small charges of Bullseye in .38 Special - 2.1 grains - are recommended in pistols but not Winchester carbines.

There are "rules of thumb" for predicting how much velocity will drop per inch of barrel that is cut off. Unfortunately, the problem is NOT that straightforward, and for any given individual barrel, the only way to find out how much you will lose (OR GAIN, which has occurred!!) is by cutting a barrel off and chronographing the load in question both before and after the cutting has been done. And then, you are stuck with the result, as it is a bit difficult to "cut it off a little longer" afterward!