My long range question = Wouldn't cylinder gap devour power on real long barrels?

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ACES&8S

ACES&8S

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I believe the Dan Wesson & lots of Smiths came out with 10"+ barrels didn't they?
I have a few Smiths in 8 3/8" barrels in 44 mag & 357 mag which I -heard- had something to do with
competition barrel length or something, I may be wrong.
The super long barrels 10"+ should really light up the cylinder gap shouldn't they?
And loose more power than they are worth producing?
Reminds me of the old western revolver with a rifle stock & long barrel, I wonder
how their performance was.
I would really have to study for reloading a modern super long barrel.
I remember Dan Wesson dominated long range at one time but wonder what length
barrel & model it was.
My son says he would buy one if we could find out some creditable info.
 
I know I could find all this info myself & come to conclusions but it makes for good jabber & I can get good reference
as well as some knowledge from real experienced people.
I don't have any other gun collectors to talk to on a regular basis or anyone who knows about makes & models
that I am interested in, except here.
 
Well I have a Ruger Super Blackhawk with a 10" barrel and it is the most accurate revolver I own. I attribute it to heavy weight and long sight radius. As for the velocities I have never checked it against my 6" model or my S&W 29 with 7" barrel so no help there.
 
I don't think the barrel length has anything to do with pressure loss through the B/C gap. Its not like there is back pressure building up in the barrel due to its length. As the bullet and gasses pushing it jump the gap, a little of the gasses/ explosion leaks out to the side and the rest of the gasses continue down the barrel pushing the bullet. The gasses don't start flowing backwards unless your barrel is obstructed. I suppose if you had a really light powder charge and a long enough barrel that the bullet started to slow down before leaving the barrel it could happen, but that would not be a normal happening
 
If the gap is kept tight then the losses are minimal and nearly independent of barrel length. A barrel gap due to the very thin profile, high pressure, and high velocity of the gases results in choked flow through the gap. This limits the losses.

Ballistic by the inch did a nice experiment with a bunch of 38/357 cartridges with barrel lengths from 1" - 18" and three different cylinder gaps, .006, .001, .000. It's interest data.
http://www.ballisticsbytheinch.com/gaptests.html

In the end the longer barrel does typically cost you a touch more loss in velocity compared to no gap but the longer the barrel the higher the velocity despite the gap loss. Choked flow is your friend.
 
Last edited:
ACES&8S said:
The super long barrels 10"+ should really light up the cylinder gap shouldn't they? And loose more power than they are worth producing?
Click to expand...

I'm not sure what exactly you're asking. . . Yes, the BC gap will continue to leak gas until the barrel pressure drops to zero. Long barrel, longer dwell time, more gas leaked, ceteris paribus.

At some (ridiculously) long barrel length, the BC gap will leak enough to reach zero pressure before the bullet exits the bore, but that's not a practical concern.
 
A longer barreled revolver will never be slower than the shorter barrel. Keep that in mind. A larger gap always bleeds more than a smaller gap, but the bullet doesn’t know the extra length is there until it reaches said length, and when positive pressure still exists, there remains to be a force accelerating the bullet. The old rule of thumb suggests there’s a 1.5% loss per thousandth of gap, but it’s not actually a linear relationship. If you run the math - revolver cartridges are typically somewhere on the order of 40-50fps per inch. An 8” running 150fps faster than a 5”, that’s a 10% gain. If your 8” has a 6thou gap, the 5” has to be a sealed breech to catch up.

Competition shooters have “minimized” their BC gaps for many years. One notable smith focused on this in modern time is Chris Roades at Bayside Customs, who trues the cylinder face to its pin bore, then sets a ~1thou BC gap. Coupled with long barrels, he’s getting near rifle velocities with heavy 357mag bullets.

Nobody ever gained speed in a revolver, nor reduced max pressure (another red herring I hear often), by cutting down a revolver barrel.

Plainly, long barrels do NOT “lose more power than they are worth.” They gain speed.
 
And the same powders that yield the highest velocities in these cartridges in a 4" barrel, are the same as for a 20" barrel. Reloading is the same, regardless of length. Namely, H110/296, Lil Gun and 300MP.
 
mcb said:
If the gap is kept tight then the losses are minimal and nearly independent of barrel length. A barrel gap due to the very thin profile, high pressure, and high velocity of the gases results in choked flow through the gap. This limits the losses.

Ballistic by the inch did a nice experiment with a bunch of 38/357 cartridges with barrel lengths from 1" - 18" and three different cylinder gaps, .006, .001, .000. It's interest data.
http://www.ballisticsbytheinch.com/gaptests.html

In the end the longer barrel does typically cost you a touch more loss in velocity compared to no gap but the longer the barrel the higher the velocity despite the gap loss. Choked flow is your friend.
Click to expand...

That link has some good info. I looked briefly at most of the ammo tested and it appears that almost every type of ammo had a point were the no gap, .001 gap and .006 gap converged, however this point varied greatly depending on the ammo. For some ammo the the 3 lines converged at 2 inches, others converged at 18" and some in between. The differences were generally smaller than I figured they be. I wonder if the differences would have been more pronounced with a gap of .01 as is common on many of the revolvers being produced today. Even .006 is pretty tight by most standards.
 
When I had a chronograph I tested many of my loads in guns of 4", 6", 7 1/2" and 8 3/8". In most cases velocities ran 10% ~ 20% higher in the longer barrels. But a lot depended on bullet weight, caliber, and powder.

A good example was that some .357 Magnum loads using Hercules 2400 gave higher velocities in the 4" barrel that in the 6" barrel, while H110 and Winchester 296 produced higher velocities in the longer barrels.

Bob Wright
 
mcb said:
If the gap is kept tight then the losses are minimal and nearly independent of barrel length. A barrel gap due to the very thin profile, high pressure, and high velocity of the gases results in choked flow through the gap. This limits the losses.

Ballistic by the inch did a nice experiment with a bunch of 38/357 cartridges with barrel lengths from 1" - 18" and three different cylinder gaps, .006, .001, .000. It's interest data.
http://www.ballisticsbytheinch.com/gaptests.html

In the end the longer barrel does typically cost you a touch more loss in velocity compared to no gap but the longer the barrel the higher the velocity despite the gap loss. Choked flow is your friend.
Click to expand...
I saved the Gap Test Site , thanks.
 
Varminterror said:
A longer barreled revolver will never be slower than the shorter barrel. Keep that in mind. A larger gap always bleeds more than a smaller gap, but the bullet doesn’t know the extra length is there until it reaches said length, and when positive pressure still exists, there remains to be a force accelerating the bullet. The old rule of thumb suggests there’s a 1.5% loss per thousandth of gap, but it’s not actually a linear relationship. If you run the math - revolver cartridges are typically somewhere on the order of 40-50fps per inch. An 8” running 150fps faster than a 5”, that’s a 10% gain. If your 8” has a 6thou gap, the 5” has to be a sealed breech to catch up.

Competition shooters have “minimized” their BC gaps for many years. One notable smith focused on this in modern time is Chris Roades at Bayside Customs, who trues the cylinder face to its pin bore, then sets a ~1thou BC gap. Coupled with long barrels, he’s getting near rifle velocities with heavy 357mag bullets.

Nobody ever gained speed in a revolver, nor reduced max pressure (another red herring I hear often), by cutting down a revolver barrel.

Plainly, long barrels do NOT “lose more power than they are worth.” They gain speed.
Click to expand...
Now that's the answer I was looking for.
 
BobWright said:
When I had a chronograph I tested many of my loads in guns of 4", 6", 7 1/2" and 8 3/8". In most cases velocities ran 10% ~ 20% higher in the longer barrels. But a lot depended on bullet weight, caliber, and powder.

A good example was that some .357 Magnum loads using Hercules 2400 gave higher velocities in the 4" barrel that in the 6" barrel, while H110 and Winchester 296 produced higher velocities in the longer barrels.

Bob Wright
Click to expand...
That is good info, thanks.
 
CraigC said:
And the same powders that yield the highest velocities in these cartridges in a 4" barrel, are the same as for a 20" barrel. Reloading is the same, regardless of length. Namely, H110/296, Lil Gun and 300MP.
Click to expand...
Almost the same. I have loaded some soft plated lead 357 that would scream from a 6” barrel but would tear apart from centrifugal force out of my buntline. Those loads are crazy hot and are above any published book max, but it is something to consider when you are pushing a pistol round as fast as you can. Your bullet has to hold up to the velocity.
 
BobWright said:
When I had a chronograph I tested many of my loads in guns of 4", 6", 7 1/2" and 8 3/8". In most cases velocities ran 10% ~ 20% higher in the longer barrels. But a lot depended on bullet weight, caliber, and powder.

A good example was that some .357 Magnum loads using Hercules 2400 gave higher velocities in the 4" barrel that in the 6" barrel, while H110 and Winchester 296 produced higher velocities in the longer barrels.

Bob Wright
Click to expand...

Interesting. I have 2 Model 29's, a 6 inch and a 4 inch. With some loads I also chronographed higher velocities out of the 4 incher ccomared to the 6 inch gun. Some barrels are just faster/slower than others.
 
WestKentucky said:
Almost the same. I have loaded some soft plated lead 357 that would scream from a 6” barrel but would tear apart from centrifugal force out of my buntline. Those loads are crazy hot and are above any published book max, but it is something to consider when you are pushing a pistol round as fast as you can. Your bullet has to hold up to the velocity.
Click to expand...
That's a completely separate issue.
 
Extracting from Ballistics by the Inch velocity figures with test barrels and various real guns (doing my own energy calc from bullet weight and velocity), BBIT got:
Code: 
.22 Magnum (WMR) CCI MaxiMag 40gr JHP
Velocity in feet per second
       Energy in foot/pounds
              Barrel length in inches
1985   350    18" test barrel
1987   350    16" test barrel
1575   220     6" test barrel
1474   193     5" test barrel
1949   337    20" Winchester Model 275 rifle
1107   108    18.5" Circuit Judge revolving carbine
1289   147     5.5" Ruger Single Six revolver
1049    97     4.6" Heritage Rough Rider revolver
The .22 Mag Circuit Judge revolving carbine is no longer on the market due to customer disappointment (BBIT noted that the overly generous forcing cone on the Circuit judge barrel probably contributed to greater loss of back pressure in the barrel resulting in even more loss of velocity.

Loss of gas pressure through the barrel cylinder gap of different models of revolving firearms does affect the velocity that might be gained from a longer barrel.

A cap'n'ball revolver with no barrel, cylinder only, acheives about 120 fps; back pressure in the barrel after the bullet transits from cylinder to barrel can raise velocity to 600 or 700 fps, but a sloppy barrel cylinder gap will have a measurable effect on how much is gained.
 
The super long barrels 10"+ should really light up the cylinder gap shouldn't they?
And loose more power than they are worth producing?
Click to expand...

Some propellant gasses (and the pressure they would exert) escape through the cylinder gap. But because the flow is highly turbulent, the losses are low. Think of ten people trying to escape a room that is on fire through a single door all at once. There is going to be quite a commotion at the door as everyone pushes and shoves to make it through the door. Someone may get out the door, maybe even a second person, but the majority will stay in the room a long time before they get out. The same happens with the propellant gas molecules; some make it out, but most are left behind in the cylinder or barrel because they weren't successful in fighting their way out of the door.

Of course the longer the bullet is in the barrel with the column of gasses pushing behind it, the more gas is going to escape through the cylinder gap, but at any practical length for a pistol barrel using anthing except parlor-trick loadings, the losses at the cylinder gap will not be enough to make the extra time the gasses get to push on the bullet through a longer barrel counter-productive.
 
Carl N. Brown said:
Extracting from Ballistics by the Inch velocity figures with test barrels and various real guns (doing my own energy calc from bullet weight and velocity), BBIT got:
Code: 
.22 Magnum (WMR) CCI MaxiMag 40gr JHP
Velocity in feet per second
       Energy in foot/pounds
              Barrel length in inches
1985   350    18" test barrel
1987   350    16" test barrel
1575   220     6" test barrel
1474   193     5" test barrel
1949   337    20" Winchester Model 275 rifle
1107   108    18.5" Circuit Judge revolving carbine
1289   147     5.5" Ruger Single Six revolver
1049    97     4.6" Heritage Rough Rider revolver
 Love true test results per users instead of mfg stuff thanks.
The .22 Mag Circuit Judge revolving carbine is no longer on the market due to customer disappointment (BBIT noted that the overly generous forcing cone on the Circuit judge barrel probably contributed to greater loss of back pressure in the barrel resulting in even more loss of velocity.

Loss of gas pressure through the barrel cylinder gap of different models of revolving firearms does affect the velocity that might be gained from a longer barrel.

A cap'n'ball revolver with no barrel, cylinder only, acheives about 120 fps; back pressure in the barrel after the bullet transits from cylinder to barrel can raise velocity to 600 or 700 fps, but a sloppy barrel cylinder gap will have a measurable effect on how much is gained.
Click to expand...
 
hdwhit said:
Some propellant gasses (and the pressure they would exert) escape through the cylinder gap. But because the flow is highly turbulent, the losses are low. Think of ten people trying to escape a room that is on fire through a single door all at once. There is going to be quite a commotion at the door as everyone pushes and shoves to make it through the door. Someone may get out the door, maybe even a second person, but the majority will stay in the room a long time before they get out. The same happens with the propellant gas molecules; some make it out, but most are left behind in the cylinder or barrel because they weren't successful in fighting their way out of the door.

Of course the longer the bullet is in the barrel with the column of gasses pushing behind it, the more gas is going to escape through the cylinder gap, but at any practical length for a pistol barrel using anthing except parlor-trick loadings, the losses at the cylinder gap will not be enough to make the extra time the gasses get to push on the bullet through a longer barrel counter-productive.
Click to expand...

Since we are using imagination, look at this 357 magnum barrel, it is --- 5 feet long--- & attached to a S&W model 19-5
I load & fire a factory Remington 125 grain JSP, how far can it travel thru the barrel & if it does stop will the result be a long thruster
type exhaust thru the c-gap or a sudden stop. I don't believe it would explode because in front of the bullet is low pressure & the
only way to disperse the pressure is thru the c-gap which I suppose would look like a cutting torch for an instant.
So that would tell us there must be a limit to where a revolver barrel can launch a bullet in the first place unless it rips the brass
hull off the lead & exits like WestKentucky described.
 
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