Any advantage to 30"+ barrels?
- Thread starter Solitar
- Start date
Magnum Man
New member
As far as accuracy goes, all other things being equal a shorter barrel rifle will tend to be more accurate than a longer one.
Lots of folks believe that shorter barrels will be more accurate than longer ones, and they have some theoretical justification for this: less vibration.
Howerver, I have found long 29" Mauser barrels to be more accurate than short carbine barrels. I also suspect, but cannot prove, that long barrels are more accurate than short barrels when both are equally worn out.
Whatever the case, there is no doubt that muzzle blast becomes more and more of an adverse factor as barrels get shorter. We are told that when the '03 Springfield with 24" barrel was adopted that the Infantry was glad to get a rifle with a barrel shorter than their previous 30 incher, while the cavelry was glad to get one longer than their previous 22 incher (Campbell, The '03 Era, 1994).
I guess the grass is always greener on the other side of the hill.
[This message has been edited by Herodotus (edited April 24, 2000).]
Howerver, I have found long 29" Mauser barrels to be more accurate than short carbine barrels. I also suspect, but cannot prove, that long barrels are more accurate than short barrels when both are equally worn out.
Whatever the case, there is no doubt that muzzle blast becomes more and more of an adverse factor as barrels get shorter. We are told that when the '03 Springfield with 24" barrel was adopted that the Infantry was glad to get a rifle with a barrel shorter than their previous 30 incher, while the cavelry was glad to get one longer than their previous 22 incher (Campbell, The '03 Era, 1994).
I guess the grass is always greener on the other side of the hill.
[This message has been edited by Herodotus (edited April 24, 2000).]
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>As far as accuracy goes, all other things being equal a shorter barrel rifle will tend to be more accurate than a longer one.[/quote]I don't know about that. The BOSS system used by Browning is a commercial example of a principle known by rifle barrel makers for years, the world over.
What you probably mean is the "stiffer" barrels are probably more accurate. And with that I agree. Of course, that means longer barrels would be thicker than normal and would be heavy. That's what we call a varminter barrel. Thin barrels are accurate when the length is cut or "damped", as in the BOSS system, at a primary vibration node maximum deflection point. Or you can vary the primary vibration frequency by the old tried and true method of finding the right "load" for that rifle. That just moves the node deflection to your barrel length. Shorter is not always more accurate for a lot of reasons.
As for velocity vs accuracy, a very simple principle shows that one does not yield the other. For a given load, there is a barrel length that yields full extension of the pressure pulse. That gives maximum velocity for that load. That barrel length may be smack between two primary vibration nodes, i.e., the worst place for accuracy. The muzzle is whipping across the boreline at this point, going from one maximum displacement to the other, not necessarily in a straight line either.
Heavy sporter barrels usually have a straight taper instead of a "hollow ground" taper. That way you get good mechanical resistance to primary vibrations without the weight of a heavy varminter barrel. Another way to make your barrel stiffer is to shorten it. That's where this started.
[This message has been edited by sensop (edited April 24, 2000).]
What you probably mean is the "stiffer" barrels are probably more accurate. And with that I agree. Of course, that means longer barrels would be thicker than normal and would be heavy. That's what we call a varminter barrel. Thin barrels are accurate when the length is cut or "damped", as in the BOSS system, at a primary vibration node maximum deflection point. Or you can vary the primary vibration frequency by the old tried and true method of finding the right "load" for that rifle. That just moves the node deflection to your barrel length. Shorter is not always more accurate for a lot of reasons.
As for velocity vs accuracy, a very simple principle shows that one does not yield the other. For a given load, there is a barrel length that yields full extension of the pressure pulse. That gives maximum velocity for that load. That barrel length may be smack between two primary vibration nodes, i.e., the worst place for accuracy. The muzzle is whipping across the boreline at this point, going from one maximum displacement to the other, not necessarily in a straight line either.
Heavy sporter barrels usually have a straight taper instead of a "hollow ground" taper. That way you get good mechanical resistance to primary vibrations without the weight of a heavy varminter barrel. Another way to make your barrel stiffer is to shorten it. That's where this started.
[This message has been edited by sensop (edited April 24, 2000).]
Magnum Man
New member
Sensop,
That's what I ment about the shorter barrel being stiffer. What I was trying to say about the accuracy is, if the only difference in the two barrels is length, the shorter barrel will tend to be more accurate.
That's what I ment about the shorter barrel being stiffer. What I was trying to say about the accuracy is, if the only difference in the two barrels is length, the shorter barrel will tend to be more accurate.
Art Eatman
Staff in Memoriam
Well, here's another "Art sorta remembers" deal. Back some 15-20 years ago, somebody got curious about "maximum" barrel length. There was some curiosity as to what length of barrel started slowing down a rifle bullet--friction had more effect on the bullet than the final stage of the powder's burning.
I believe the cartridge was in the medium class; '06 or .308 or some similar.
About all I recall is that the maximum velocity occurred at around 33" length.
But don't quote me.
FWIW, Art
I believe the cartridge was in the medium class; '06 or .308 or some similar.
About all I recall is that the maximum velocity occurred at around 33" length.
But don't quote me.
FWIW, Art
Hi, Art,
I recall the same thing, around 33-36 inches was max velocity. After that, the friction began to overcome the decreasing pressure. I think for the .22 LR, it is 16".
I don't think anyone ever built a barrel long enough to see if the bullet would actually stop, but it would be an interesting idea.
Jim
I recall the same thing, around 33-36 inches was max velocity. After that, the friction began to overcome the decreasing pressure. I think for the .22 LR, it is 16".
I don't think anyone ever built a barrel long enough to see if the bullet would actually stop, but it would be an interesting idea.
Jim
Art Eatman
Staff in Memoriam
Hey, Jim...
Yeah, somewhere down the line the gas pressure wouldn't be able to push the bullet all the way out.
However, opening the bolt might be an interesting exercise!
Hmmm. Force = Pressure times Area. The area of the base of, say, a .30 bullet is .308 X .308 X 3.1416...or about 0.3 square inches. Now we need to know the force to push a bullet down the barrel. I guess you could set up a hydraulic ram and use a pressure gauge while pushing the little doofer.
Some powder company oughta know the volume of gas produced from a charge, and the pressure curve as it expands down the barrel...
Hey! Apply for a federal grant? The ultimate safe gun: The bullet won't come out. Send the first one to Schumer's bodyguard...
, Art
Yeah, somewhere down the line the gas pressure wouldn't be able to push the bullet all the way out.
However, opening the bolt might be an interesting exercise!
Hmmm. Force = Pressure times Area. The area of the base of, say, a .30 bullet is .308 X .308 X 3.1416...or about 0.3 square inches. Now we need to know the force to push a bullet down the barrel. I guess you could set up a hydraulic ram and use a pressure gauge while pushing the little doofer.
Some powder company oughta know the volume of gas produced from a charge, and the pressure curve as it expands down the barrel...
Hey! Apply for a federal grant? The ultimate safe gun: The bullet won't come out. Send the first one to Schumer's bodyguard...
Thanks for the feedback folks!
When I get flush enough to get a 300 or heavier ultramag or something similar, then maybe a custom 32 inch heavy "varminter" barrel may be the next best thing to a .50 BMG.
Seriously, I am considering something that can really reach out to several hundred yards with great accuracy. I'd rather not go the .50 BMG route since 1) the rifles are ugly, 2) the ammo is expensive, 3) the rifles are VERY heavy, 4) did I say they were ugly! Compare any of the .50 BMG's to one of these http://www.remington.com/Firearms/CUSTOM/700AWR.HTM
p.s. somebody here used a "barfing" emoticon. How did you do that?
When I get flush enough to get a 300 or heavier ultramag or something similar, then maybe a custom 32 inch heavy "varminter" barrel may be the next best thing to a .50 BMG.
Seriously, I am considering something that can really reach out to several hundred yards with great accuracy. I'd rather not go the .50 BMG route since 1) the rifles are ugly, 2) the ammo is expensive, 3) the rifles are VERY heavy, 4) did I say they were ugly! Compare any of the .50 BMG's to one of these http://www.remington.com/Firearms/CUSTOM/700AWR.HTM
p.s. somebody here used a "barfing" emoticon. How did you do that?
Hart Industries Defense
Moderator
You are right; I did much research on this topic while developing the only 50AP body armour in the world (see at http://www.americanwhitelinen.com/ click on military surplus.
Approximately only 22 times the volume of air volume is produced by an exploding bullet powder. That means that if you know the amount of grains your bullet casing holds; only 22 times that volume will in essence provide the pushing power.
After that it becomes a 'suction' to slow your bullet down. However, if you have a piston driven gun; sometimes you can have less push or sometimes the suction is abated because there is an open air hole left by the already moving piston.
A slow bullet is not bad except when you need distance.
[This message has been edited by Schmit (edited April 25, 2000).]
Approximately only 22 times the volume of air volume is produced by an exploding bullet powder. That means that if you know the amount of grains your bullet casing holds; only 22 times that volume will in essence provide the pushing power.
After that it becomes a 'suction' to slow your bullet down. However, if you have a piston driven gun; sometimes you can have less push or sometimes the suction is abated because there is an open air hole left by the already moving piston.
A slow bullet is not bad except when you need distance.
[This message has been edited by Schmit (edited April 25, 2000).]
Hart Industries Defense
Moderator
Several years back I did much research on pressure and bullets while developing the only 50cal AP body armour in the world. Check out military surplus at http://www.americanwhitelinen.com/ (please see comment on 22x vol of grains in answers)
[This message has been edited by Schmit (edited April 25, 2000).]
[This message has been edited by Schmit (edited April 25, 2000).]