im just curious if there is a magic length where a longer barrel no longer gains you any speed at all. for instance whould a 40 inch barrel be any faster than a 31 inch barrel.
Gunsmithing barrel length and velocity
- Thread starter 42769vette
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Re: barrel length and velocity
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 42769vette</div><div class="ubbcode-body">im just curious if there is a magic length where a longer barrel no longer gains you any speed at all. for instance whould a 40 inch barrel be any faster than a 31 inch barrel.
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Tag for a damn interesting question.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 42769vette</div><div class="ubbcode-body">im just curious if there is a magic length where a longer barrel no longer gains you any speed at all. for instance whould a 40 inch barrel be any faster than a 31 inch barrel.
</div></div>
Tag for a damn interesting question.
Re: barrel length and velocity
ya i have no intentions on puttting a 40 inch barrel on a rifle, im just curious more than anything else
ya i have no intentions on puttting a 40 inch barrel on a rifle, im just curious more than anything else
Re: barrel length and velocity
Depends on caliber and cartridge case. You reach a point of diminishing returns with barrel length. With a 338 Lapua Improved you get most of the velocity out of it at 30". Go to 40" and yes you can get a small gain,3-4% in velocity but you may give up accuracy and it will look like a WWII German artilery piece on a rail car. Big 30's benefit more but I've never seen a reason to go past 34"
Depends on caliber and cartridge case. You reach a point of diminishing returns with barrel length. With a 338 Lapua Improved you get most of the velocity out of it at 30". Go to 40" and yes you can get a small gain,3-4% in velocity but you may give up accuracy and it will look like a WWII German artilery piece on a rail car. Big 30's benefit more but I've never seen a reason to go past 34"
Re: barrel length and velocity
thanks dave, what about a fclass gun like the 6.5x284 or other 6.5-7mm guns
thanks dave, what about a fclass gun like the 6.5x284 or other 6.5-7mm guns
Re: barrel length and velocity
You have plenty of weight to work with in a F Class gun but I don't think you need more than 28-30". I would be more concerned about the balance of the rifle more than barrel length. One more thing I wouldn't worry about having enough length to rechamber the barrel. A 6.5-284 is not kind to the interior finish. The finish will deteriorate so far down the barrel that it won't make sense to rechamber. 284's will last longer but again you don't need the barrel length.
You have plenty of weight to work with in a F Class gun but I don't think you need more than 28-30". I would be more concerned about the balance of the rifle more than barrel length. One more thing I wouldn't worry about having enough length to rechamber the barrel. A 6.5-284 is not kind to the interior finish. The finish will deteriorate so far down the barrel that it won't make sense to rechamber. 284's will last longer but again you don't need the barrel length.
Re: barrel length and velocity
Just pick a different caliber. As the bullet travels down the bore some of the jacket is ground off. It seems like the bullet would eventually have a loose fit to the bore, even though its tighter at the muzzle. I want the bullet gone as soon as it is stable.
Just pick a different caliber. As the bullet travels down the bore some of the jacket is ground off. It seems like the bullet would eventually have a loose fit to the bore, even though its tighter at the muzzle. I want the bullet gone as soon as it is stable.
Re: barrel length and velocity
I've actually been thinking about this a lot lately also.
When my 300wm was used primarily for hunting, I had no problem shortening if from 24" to 22". So I lost 40-50 fps?
But now that I'm engaging steel at further and further distances, velocity is becoming more important to me. I'm planning on rebarreling in the spring. Is there an appreciable benefit in velocity for a 300WM increasing from 26" to 28" or 30"?
John
I've actually been thinking about this a lot lately also.
When my 300wm was used primarily for hunting, I had no problem shortening if from 24" to 22". So I lost 40-50 fps?
But now that I'm engaging steel at further and further distances, velocity is becoming more important to me. I'm planning on rebarreling in the spring. Is there an appreciable benefit in velocity for a 300WM increasing from 26" to 28" or 30"?
John
Re: barrel length and velocity
Depending on the powder you are using. Slower burning powders benefit more from longer barrels than faster burning powders. I know my 28" 284 was getting 3100 from 175 Match kings from a 28" barrel and RE17, The longer barrel allowed for a more complete powder burn. My 6xc with 26" barrel is not getting as complete a burn and the velocities are not what I expected either.
Depending on the powder you are using. Slower burning powders benefit more from longer barrels than faster burning powders. I know my 28" 284 was getting 3100 from 175 Match kings from a 28" barrel and RE17, The longer barrel allowed for a more complete powder burn. My 6xc with 26" barrel is not getting as complete a burn and the velocities are not what I expected either.
Re: barrel length and velocity
My buddy chronographed a load shot from his 26" .308, and then chronographed it after I cut it down to 20", he says he only lost like 100fps.
I wasnt there to confirm, but I noticed almost the same thing in my .243. I cut it down from 26" to 20.5" and lost no more than 200(a guess based on trajectory).
Quickload "confirmed" my guess.
I never realized how little you gain from barrel length over 20-24"
I'd then imagin that from 24" to 30", you'd gain even less. And so on from 30" and up...
My buddy chronographed a load shot from his 26" .308, and then chronographed it after I cut it down to 20", he says he only lost like 100fps.
I wasnt there to confirm, but I noticed almost the same thing in my .243. I cut it down from 26" to 20.5" and lost no more than 200(a guess based on trajectory).
Quickload "confirmed" my guess.
I never realized how little you gain from barrel length over 20-24"
I'd then imagin that from 24" to 30", you'd gain even less. And so on from 30" and up...
Re: barrel length and velocity
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">My buddy chronographed a load shot from his 26" .308, and then chronographed it after I cut it down to 20", he says he only lost like 100fps.
I wasnt there to confirm, but I noticed almost the same thing in my .243. I cut it down from 26" to 20.5" and lost no more than 200(a guess based on trajectory).
Quickload "confirmed" my guess.
I never realized how little you gain from barrel length over 20-24"
I'd then imagin that from 24" to 30", you'd gain even less. And so on from 30" and up... </div></div>
This is pretty much what I ran into. I get 2860 fps from 208's in my 22" barrel using almost identical load that Rob01 is getting 2950'ish from his 26".
So, I guess I can count on getting to those speeds with a 26", but is there really anything to be gained by going longer?
John
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: AZPrecision</div><div class="ubbcode-body">My buddy chronographed a load shot from his 26" .308, and then chronographed it after I cut it down to 20", he says he only lost like 100fps.
I wasnt there to confirm, but I noticed almost the same thing in my .243. I cut it down from 26" to 20.5" and lost no more than 200(a guess based on trajectory).
Quickload "confirmed" my guess.
I never realized how little you gain from barrel length over 20-24"
I'd then imagin that from 24" to 30", you'd gain even less. And so on from 30" and up... </div></div>
This is pretty much what I ran into. I get 2860 fps from 208's in my 22" barrel using almost identical load that Rob01 is getting 2950'ish from his 26".
So, I guess I can count on getting to those speeds with a 26", but is there really anything to be gained by going longer?
John
Re: barrel length and velocity
Might not apply 1:1 across all applications but might be of interest, might not be...
http://www.riflebarrels.com/articles/bullets_ballastics/long_barrel_velocity.htm
Might not apply 1:1 across all applications but might be of interest, might not be...
http://www.riflebarrels.com/articles/bullets_ballastics/long_barrel_velocity.htm
Re: barrel length and velocity
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Brain</div><div class="ubbcode-body">Might not apply 1:1 across all applications but might be of interest, might not be...
http://www.riflebarrels.com/articles/bullets_ballastics/long_barrel_velocity.htm </div></div>
very interesting and exactly what i was curious about.
like i said i dont plan on doing this but was just curious what testing had been done on the issue
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Brain</div><div class="ubbcode-body">Might not apply 1:1 across all applications but might be of interest, might not be...
http://www.riflebarrels.com/articles/bullets_ballastics/long_barrel_velocity.htm </div></div>
very interesting and exactly what i was curious about.
like i said i dont plan on doing this but was just curious what testing had been done on the issue
Re: barrel length and velocity
depends a lot on the way or the rate the powder burns, but there is a calculable length where bullet friction over rides velocity potential. that length is generally longer than practical.
JR
depends a lot on the way or the rate the powder burns, but there is a calculable length where bullet friction over rides velocity potential. that length is generally longer than practical.
JR
Re: barrel length and velocity
I use 28" with my .260, Savage puts a 30" on their F Class Open 6.5-284 rigs, and they clean house.
It's the last part of the barrel, where the velocity is up there, where the most copper fouling supposedly occurs. I don't think that's good for either the bullets in particular or for accuracy in general. Once velocity gains begin to drop off proportionally, I'd cut the barrel length there. Same is true for powder charge increments, I believe the additional pressure is just causing excessive obturation, excessive fouling, and the increased friction robs much of any potential velocity gains
Greg
I use 28" with my .260, Savage puts a 30" on their F Class Open 6.5-284 rigs, and they clean house.
It's the last part of the barrel, where the velocity is up there, where the most copper fouling supposedly occurs. I don't think that's good for either the bullets in particular or for accuracy in general. Once velocity gains begin to drop off proportionally, I'd cut the barrel length there. Same is true for powder charge increments, I believe the additional pressure is just causing excessive obturation, excessive fouling, and the increased friction robs much of any potential velocity gains
Greg
Re: barrel length and velocity
Greg,
You might think so but most of all the obturation has been done under extreme pressure about an inch and half from the throat. and it should be that first inch and half that copper fouls more than the last. you would have higher velocities on a 40" 6.5 x 284 barrel than a 30", still has the residual pressure to keep driving..
Greg,
You might think so but most of all the obturation has been done under extreme pressure about an inch and half from the throat. and it should be that first inch and half that copper fouls more than the last. you would have higher velocities on a 40" 6.5 x 284 barrel than a 30", still has the residual pressure to keep driving..
Re: barrel length and velocity
OK, I defer.
L-W (my maker) sells barrels to 28" without extra charge, and blanks to 32". Beyond that; I have no idea.
Greg
OK, I defer.
L-W (my maker) sells barrels to 28" without extra charge, and blanks to 32". Beyond that; I have no idea.
Greg
