ok this maybe a stupid question, but I will put it to you anyways. How much of a noticeable difference does the barrel length from 16", 18", and 20" have on a semi auto .308? what difference does it make at all (other than length)?
length of barrels
- Thread starter jsmythe
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Re: length of barrels
about 50fps per inch of barrel, also have to consider weight. What are you trying to do?
about 50fps per inch of barrel, also have to consider weight. What are you trying to do?
Re: length of barrels
Longer barrel, heavier, faster, less noise.
Shorter barrel lighter, louder, at least as accurate if not more so, more adapted to CQ in car or building.
50 fps is a bit high for the spread IMO, but it depends on what length, ie 18-20 or 11-13 etc. Also ctg and powder make a difference in what is gained or lost.
Longer barrel, heavier, faster, less noise.
Shorter barrel lighter, louder, at least as accurate if not more so, more adapted to CQ in car or building.
50 fps is a bit high for the spread IMO, but it depends on what length, ie 18-20 or 11-13 etc. Also ctg and powder make a difference in what is gained or lost.
Re: length of barrels
About 20-25 fps per inch. The exact velocity you get out of a certain length will vary based on your individual barrel.
About 20-25 fps per inch. The exact velocity you get out of a certain length will vary based on your individual barrel.
Re: length of barrels
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BCP</div><div class="ubbcode-body">About 20-25 fps per inch. The exact velocity you get out of a certain length will vary based on your individual barrel.
This is right on, as BCP said, "vary based on your individual barrel". There have been many tests over the years on this subject. Taking a rifle, firing over a chrono, cutting that barrel an inch at a time, firing over a chrono, and on and on, sometimes down to like 10 inches. Sometimes the vel. increases after an inch or two has been cut off. In test I've read about, no shooting was done for group size, just velocity. The barrel to velocity figures are a rule of thumb, based on large numbers of barrels of like bore, how they were rifled etc., but the actual number boils down to that tube. (of course within reason, it is doubtful a 10in will have higher numbers than a 20in). There are many that feel a shorter tube is more stable, and gives you a better chance of achieving good groups, again within the limits of the round.
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<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BCP</div><div class="ubbcode-body">About 20-25 fps per inch. The exact velocity you get out of a certain length will vary based on your individual barrel.
This is right on, as BCP said, "vary based on your individual barrel". There have been many tests over the years on this subject. Taking a rifle, firing over a chrono, cutting that barrel an inch at a time, firing over a chrono, and on and on, sometimes down to like 10 inches. Sometimes the vel. increases after an inch or two has been cut off. In test I've read about, no shooting was done for group size, just velocity. The barrel to velocity figures are a rule of thumb, based on large numbers of barrels of like bore, how they were rifled etc., but the actual number boils down to that tube. (of course within reason, it is doubtful a 10in will have higher numbers than a 20in). There are many that feel a shorter tube is more stable, and gives you a better chance of achieving good groups, again within the limits of the round.
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Re: length of barrels
I can tell you comparing my 14.5" POF 308 with a 16" I lose about 30 fps with similar rounds (168 match ammo). Just happened to have checked this yesterday at range with a guy that had the same gun in 16".
I can tell you comparing my 14.5" POF 308 with a 16" I lose about 30 fps with similar rounds (168 match ammo). Just happened to have checked this yesterday at range with a guy that had the same gun in 16".
Re: length of barrels
Make sure you compare like to like.
My 21" Noveske is faster than my 26" Remington 700 with some loads. Obviously a 16" Noveske would be slower than the 21
It's really going to boil down to your intended use.
Make sure you compare like to like.
My 21" Noveske is faster than my 26" Remington 700 with some loads. Obviously a 16" Noveske would be slower than the 21
It's really going to boil down to your intended use.
Re: length of barrels
I don't think its constant, meaning you can't say you loose x velocity per inch. Don't work that way.
here is an example. My granddaughter did a science project along this subject. Her ideal was to see how short you can make a hunting rifle to give you 1800 ft lbs of energy to hunt elk at 300 yards. She took a 26 inch 308 barrel, cut it off 2 inches at a time to 16 checking the velocity and energy. She was discussing hunting ammo, so used factory Remington 180 grn ammo. Here is her results.
!st col is barrel lenght, followed by MV, ME, then 300 yard vel & energy.
26 2826 fps 3,192 2240 2,005
24 2722 fps 2,961 2149 1,846
22 2713 fps 2,942 2141 1,832
20 2677 fps 2,864 2109 1,778
18 2654 fps 2,815 2089 1,744
16 2552 fps 2,603 2000 1,599
I don't think its constant, meaning you can't say you loose x velocity per inch. Don't work that way.
here is an example. My granddaughter did a science project along this subject. Her ideal was to see how short you can make a hunting rifle to give you 1800 ft lbs of energy to hunt elk at 300 yards. She took a 26 inch 308 barrel, cut it off 2 inches at a time to 16 checking the velocity and energy. She was discussing hunting ammo, so used factory Remington 180 grn ammo. Here is her results.
!st col is barrel lenght, followed by MV, ME, then 300 yard vel & energy.
26 2826 fps 3,192 2240 2,005
24 2722 fps 2,961 2149 1,846
22 2713 fps 2,942 2141 1,832
20 2677 fps 2,864 2109 1,778
18 2654 fps 2,815 2089 1,744
16 2552 fps 2,603 2000 1,599
Re: length of barrels
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kraigWY</div><div class="ubbcode-body">My granddaughter did a science project along this subject.
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Nice work, I bet she got an A+++
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kraigWY</div><div class="ubbcode-body">My granddaughter did a science project along this subject.
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Nice work, I bet she got an A+++
Re: length of barrels
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kraigWY</div><div class="ubbcode-body">
!st col is barrel lenght, followed by MV, ME, then 300 yard vel & energy.
26 2826 fps 3,192 2240 2,005
24 2722 fps 2,961 2149 1,846
22 2713 fps 2,942 2141 1,832
20 2677 fps 2,864 2109 1,778
18 2654 fps 2,815 2089 1,744
16 2552 fps 2,603 2000 1,599
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That is a pretty fat loss between 16 and 18. I always suspected that going 16" on a .308 was cutting the legs out. I still may have to try some day.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kraigWY</div><div class="ubbcode-body">
!st col is barrel lenght, followed by MV, ME, then 300 yard vel & energy.
26 2826 fps 3,192 2240 2,005
24 2722 fps 2,961 2149 1,846
22 2713 fps 2,942 2141 1,832
20 2677 fps 2,864 2109 1,778
18 2654 fps 2,815 2089 1,744
16 2552 fps 2,603 2000 1,599
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That is a pretty fat loss between 16 and 18. I always suspected that going 16" on a .308 was cutting the legs out. I still may have to try some day.
Re: length of barrels
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kraigWY</div><div class="ubbcode-body">I don't think its constant, meaning you can't say you loose x velocity per inch. Don't work that way.
here is an example. My granddaughter did a science project along this subject. Her ideal was to see how short you can make a hunting rifle to give you 1800 ft lbs of energy to hunt elk at 300 yards. She took a 26 inch 308 barrel, cut it off 2 inches at a time to 16 checking the velocity and energy. She was discussing hunting ammo, so used factory Remington 180 grn ammo. Here is her results.
!st col is barrel lenght, followed by MV, ME, then 300 yard vel & energy.
26 2826 fps 3,192 2240 2,005
24 2722 fps 2,961 2149 1,846
22 2713 fps 2,942 2141 1,832
20 2677 fps 2,864 2109 1,778
18 2654 fps 2,815 2089 1,744
16 2552 fps 2,603 2000 1,599
</div></div>I am very happy to see we still have some great kids in the US! I know you are proud of her, I wouldn't know her from Eve, but I'm proud of her!
I wanted to add something to this thread, it is very common to have two rifles of the same caliber,but different BBL lgth, shooting the same ammo, same day etc., over a crono and have the shorter rifle shoot at a higher velocity. So many factors are involved that these "rules of thumb" are kind of like "wives tales". Your GD is First Class-I too hope she received an A+ on her report!
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kraigWY</div><div class="ubbcode-body">I don't think its constant, meaning you can't say you loose x velocity per inch. Don't work that way.
here is an example. My granddaughter did a science project along this subject. Her ideal was to see how short you can make a hunting rifle to give you 1800 ft lbs of energy to hunt elk at 300 yards. She took a 26 inch 308 barrel, cut it off 2 inches at a time to 16 checking the velocity and energy. She was discussing hunting ammo, so used factory Remington 180 grn ammo. Here is her results.
!st col is barrel lenght, followed by MV, ME, then 300 yard vel & energy.
26 2826 fps 3,192 2240 2,005
24 2722 fps 2,961 2149 1,846
22 2713 fps 2,942 2141 1,832
20 2677 fps 2,864 2109 1,778
18 2654 fps 2,815 2089 1,744
16 2552 fps 2,603 2000 1,599
</div></div>I am very happy to see we still have some great kids in the US! I know you are proud of her, I wouldn't know her from Eve, but I'm proud of her!
I wanted to add something to this thread, it is very common to have two rifles of the same caliber,but different BBL lgth, shooting the same ammo, same day etc., over a crono and have the shorter rifle shoot at a higher velocity. So many factors are involved that these "rules of thumb" are kind of like "wives tales". Your GD is First Class-I too hope she received an A+ on her report!
