Barrel length and velocity??

[Ionian]

  At what length does a barrel become pure decoration? I think after the first 24 to 26 inches all the powder would have burned up, or am I wrong and just thinking of smokeless?
  If the powder burns up in that short span, the increased accuray of a longer barrel would come from the longer sight distance and the extra length would start to cause more friction would it not?
 

[Daryl]

Even with smokeless barrels, the longer the barrel, the higher the velocity.  22LR's are a bit different. In .22's and past about 26" of barrel, there will actually start to be a drop in velocity as there isn't enough gas produced by that little case to keep expanding in the tube over the friction of the bullet. Modern smokeless centrefires will gain speed to as long a barrel as you can purchase for them - about 30" in .33cal and smaller.  The larger .50's for benchrest shooting are longer, of course. The greater the capacity of the case,the longer the barrel can be and still gain speed.
  In muzzleloaders, much the same situation is evident. The more powder you put in, the higher the speed.  Now, if you restricted your charge to say 30gr. in a .50, there would be a point where increased barrel length would decrease velocity.  If you reverse this to say a 26" barrel, each increase in powder charge will increase speed until you don't want to put any more in - slightly.  A 50" barrel will give higher speed than will a 30" or 26" barrel - absolutely - if you feed it appropriately.

 My own .69 rifle, with a 30" barrel proved higher speed with increased charges all the way from 82gr. to 365gr.  Increasing the charge from 225gr.(1,700fps) to 365gr. (1,770fps) increased the speed only 70fps, but it did increase it. This is due to the increased 'load' (pressure) causing more of the charge to burn which produces more gas which propells the ball faster.  Had I increased the charge further, I am certain that with every increasing charges, there would come a charge which would cause a reduced velocity, but that would not be a feasible charge to shoot.

[Ionian]

Daryl, doesn't barrel length get you the same results as increased charges? What I'm getting at is that at some point the length is no longer getting results that are worth the extra weight.
If you load two rifles with the same charge in a 30 inch barrel and say a 36 inch barrel, is the gain in velocity that much greater?

[Daryl]

The increasd sight radius is worth the extra length if the rifle design allows or calls for it.

 Can you get the same velocity from a 36" with 80gr. as it takes from a 30" using 100gr."?  I doubt it, but for someone with both, it might be worth the experiment.

The 36" will give a higher velocity than a 30" with the same load of course.  Is it worth it?  That depends. Since I lead towards period rifles, a rifle that should have a 36" could look mighty funny with a 30" barrel.  In that case, it's not about velcoity, but about esthetics.  A 1/2 stocked rifle looks right with either, if both are stocked proportionately to the barrel length and weight of the barrel.  I don't find a 36" barrel to be ungainly and as to weight, as long as it's under 10 1/2 pounds it's just fine.  For hunting, 42" is just fine around here. We don't have heavy underbrush in the areas I hunt, so length is not important - esthetics is along with a descent load to achieve a nice flat trajectory.

[Dphariss]

  At what length does a barrel become pure decoration? I think after the first 24 to 26 inches all the powder would have burned up, or am I wrong and just thinking of smokeless?
  If the powder burns up in that short span, the increased accuray of a longer barrel would come from the longer sight distance and the extra length would start to cause more friction would it not?
 

The longer barrel will produce more velocity. It also produces less blast and flash. The longer barrel is easy to hit with in offhand shooting as well.
BP and Smokeless are very much not the same thing. Some smokeless pistol cartridges will develope maximum pressure before the bullet gets much past the end of the cartridge case.

The GAS EXPANSION is what drives the ball. The hot gases continue to expand even after the powder is done burning. I think you will find that shortening the barrel to 24-26 will reduce the amount of powder you can use efficiently. I.E. a 40" barrel will use more powder to gain higher velocity where a 24" barrel will run out of room to burn the powder and increases in charge will produce little in the way of velocity increase.
The formula below seems to work fairly well.

I forget where I found this.
Dan


The "Davenport" formula is 11.5 grains per cubic inch of barrel.

To find the cubic inch, you first determine the diameter of the bore, divide it by two to get the radius, and then multiply the radius times itself( squaring the radius), and then multiply that number times PI( 3.1416) to get the area. of the bore. I multiple that times the 11.5 to get that coefficienct for each caliber. Then its simple to multiply that coefficient times the various barrel lengths to complete the formula and get the total powder for the cubic inches of barrel. You have to scratch your memory, unless you are a math person, or engineer, to remember the formula you learned in high school, or Jr. High, I suspect these days, to determine the area, and then cube of a circle/cylinder. Area of a circle it PiR squared. Then you determine the length of the cylinder( bore) and multiply that coefficent times the length, to get the cubic space, and then multiply that number times 11.5 grain, to get the max. charge of powder the barrel will burn.

[Ionian]

 Thank you for all the information. I would never dream of short barrels on longrifles, I was just curious of where the longer barrel would become detrimental. Weight was never a concern, I shoot high power and my M-14 is over 11 lbs. and it has never been a problem. Again, thanks for the help.

[northmn]

I have heard some get all excited when I mentioned a longer barrel shooting with more velocity.  One individual claimed an increase in velocity when he shortened his barrel.  Looking at various published chronographed loads and some of my experience I will state that IN GENERAL a longer barrel will give more velocity.  If you put 10 45's, or 50's or 54's with a 42 inch barrel against 10 with a 32 inch barrel and take average velocities the longer barrel group will have a higher velocity.  Lyman tested a Douglas barrel and got the highest velocity with the same loads in a 45 with a 28 inch barrel.  With a 36, 50 and 54 the nod went to the longer barrels by about 100 fps for heavier charges.  About 10 inches of barrel gave 10 grains equivalent increase.  Why the 45 did better with a shorter barrel is anyone's guess.  In building a rifle, I do not feel that there is enough difference between most normal ML barrel lengths say between 32 and 46 inches to let barrel length be a factor either way.  I have a 42 inch 54 and plan on making a shorter "English" style 54 for convenience when hunting.   If one needs more power you need to get a bigger bore with a round ball rifle.  Period.

DP

[longcruise]

The probelm with comparing velocities from differing barrel lengths by using two different same caliber rifles is that the barrel dimensions and condition can play a large part.

I once compared a 32" .54 to a 28" .54 on the same day with the same loading components, etc.  The 28" barrel shot a bit over 100 fps faster than the 32"!  If memory serves, the charge was 100 grains of ff.

I have a 24" .50 cal that only makes it to 1425 fps with 80 grains of 3f and that's with a tight patch/ball combo.   I'm convinced that there are other 24" barrels out there that would shoot the same combo faster.

[Dphariss]

The probelm with comparing velocities from differing barrel lengths by using two different same caliber rifles is that the barrel dimensions and condition can play a large part.

I once compared a 32" .54 to a 28" .54 on the same day with the same loading components, etc.  The 28" barrel shot a bit over 100 fps faster than the 32"!  If memory serves, the charge was 100 grains of ff.

I have a 24" .50 cal that only makes it to 1425 fps with 80 grains of 3f and that's with a tight patch/ball combo.   I'm convinced that there are other 24" barrels out there that would shoot the same combo faster.

Try this for thought.
A rougher barrel will give more velocity than a smooth one. Read W Greener. "The Gun" 1830.
I replaced a rough barrel with a smooth one in my 16 bore and LOST 150 fps. All else being the same. Breech, vent, powder, ball etc.
Dan

[Daryl]

Mike - my .50 21" Canoe gun averaged 1,468 fps with 80gr. 3F GOEX. I odnt' have th lot number, but it was from 25 pounds purchased last August. .020" denim and .495" ball, LHV lube.

  This is roughly the same velocity Taylor gets from his Virginia rifle's 42" or 44" .50 barrel, same ball, patch & lube, but with 80gr. 2F.

[northmn]

Comparing 3f to 2f can open another can of worms.  Generally 3f is about 20-30 grains worth of 2f hotter.  When I chronographed my 54 90 grains of 3f was nearly as fast as 120 2f.  it also had a wider max. spread.  Whether it would matter in a hunting load is doubtful.  A rougher barrel likely acts somewhat like a fouled barrel, which also tends to up velocities.  One thing to remember in Lyman's data is that they used the same barrel and sawed it off to various lengths.  Comparing two different barrels with the same load increases the variables.  80 grains of 3f in my 50 with a 36 inch barrel was over 1800 fps. I found the 90 grain load I had been using to be a waste of powder as the gains were not there.

DP

[longcruise]

A rougher barrel will give more velocity than a smooth one. Read W Greener. "The Gun" 1830.

I observed the same when comparing before and after velocities of a .54 barrel that I had firelapped.  It lost about 150 fps with a 110 grain load of ff.  Accuracy benefits more than made up for the loss of velocity!

[jerrywh]

The old Layman black powder handbook from 1976 has the lowdown on this . There is a big difference between a 42" and a 32" in velocity and ft. lbs energy with the same powder charge. In fact it has convinced me to build myself another longrifle.   

[Harnic]

@!*%!  I knew this would happen!  I just convinced myself to cut 6" off my 42x1" fullstock flint Hawken to balance it better & you guys come up with this!  I need a sky-hook!

[D. Taylor Sapergia]

That's exciting Jerry.  What do you have in mind?

[northmn]

@!*%!  I knew this would happen!  I just convinced myself to cut 6" off my 42x1" fullstock flint Hawken to balance it better & you guys come up with this!  I need a sky-hook!

Cut it off.  If you cannot shoot it it don't matter how much harder it hits.  I personally like a one inch 50 at about 34 inches.  My 36 inch 50 gave 1870 fps with 80 grains of 3f.  that isn't all bad for what you use a 50 on.  Also you can make up some for any extra loss by using a little more powder.  Sometimes you do not lose anything. 

DP

[jerrywh]

Taylor.
  In the past when ever I made a gun for myself I couldn't help carving and engraving it. It always ended up too nice for me to want to go hunting with. I then sold it for a nice pile of money and bought a Thompson center or something to hunt with.  I sold the last one for $16,000 and then went out and bought a great plains rifle. I said all that to say I just want a plain long rifle. Well almost plain anyway. Probably a late flint like a Fortney. I like the faster late flint locks and a 42" barrel with a 1:66 twist. or a 1:56 twist.   In the past I have always used Getz barrel but I can't seem to get one anymore.
  I have one of Chambers's best advanced large Siler locks. I think I will put a roller frizzen on it. I have all the hardware that I cast previously and a fantastic piece of eastern maple from Freddie Harrison that is about 12 years old. I'm only going to make three more guns for sale. If Obama will permit. I am addicted to 54 calibers. I'm selling all my stock of wood and parts slowly. I have some real nice English walnut stock wood , long enough for anything.

[Mike R]

If you have access to the 1st edition of the Lyman BP loading manual you can see the effect of longer barrel vs shorter barrel in their charts: for most calibers they show vel/me comparisons for various loads and various barrel lengths.  IN GENERAL, these charts show that higher vel/me accompanies increased barrel length.  Their charts generally go from 28" to 44" barrels.  In some cases the increase in vel is substantial with longer barrels.

[Daryl]

Go ahead and cut it off, Harry.  36" is all it needs anyway.  If you want, bring it to Heffley next year and I'll bring an old meat saw or something  else that will work OK.   I'll bring my muzzle-crowning pocket knife too.  I suppose I'll have to bring my sharpening sticks as the GM barrels are a bit harder than the TC barrels I've crowning with that knife. A slip of old emery along with some elbow grease and we'll have her shooting plum centre.

[Harnic]

DP & Daryl, thanks for your input.  I have decided to chop it off at 36".  As I don't hunt I have no need for the extra velocity a longer barrel provides, the targets can't tell any difference.   I think I'll use my lathe thanks Daryl.  I'll have a chunk of barrel left over to make a nice short belt pistol too!  I've always wanted a flint derringer.

[Dphariss]

A rougher barrel will give more velocity than a smooth one. Read W Greener. "The Gun" 1830.

I observed the same when comparing before and after velocities of a .54 barrel that I had firelapped.  It lost about 150 fps with a 110 grain load of ff.  Accuracy benefits more than made up for the loss of velocity!

From what I have read the British used to intentionally roughen shotgun bores for a distance up from the breech to increase velocity. The increased friction builds pressure and makes for a better burn of the powder.
I have had "problems" with a rifle barrel that was both rough and had serious internal dimension problems. But it produced 150 fps better velocity that the smooth and very much better shooting barrel I replaced it with.

Dan

[James Rogers]

From what I have read the British used to intentionally roughen shotgun bores for a distance up from the breech to increase velocity.
Dan

We must have read the same material.     The roughened breech end occurred along with a flared muzzle end(internally) to create a primitive from of "choking". This is how most distinguish a fusee from a fowling piece along with barrel wall thickness.

The down side of that for shot could be deformation upon ignition.

[northmn]

Roughening shotgun bores at the muzzle was an old market hunters trick also.  It eliminated the 'donut holes" in patterns as it slowed the wads and not the shot so that the wads do not slam into the shot on exit. A form of choke.  May have speeded up the loads but may have had more to do with pattern.  I just took out a full choke on a shotgun I just made.  It needs honing and polishing as it still shoots tighter than I really want.  I think it is due to the roughness of the choke end.  It patterns great so I may leave it. 

DP

[Daryl]

DP- with normally lubed and snug fitting wads, the 'roughness' will be wiped clean each time it's loaded.  Greener aluded tothe 'roughening' upof the muzzles to retard the cushion wads from punching holes in the patterns, but said they fouled qui9ckly, rendering the roughness less effective.  When loading Taylor's Manton, I watched the wads easily clean the tube when loading and figured if roughened, it-too would be cleaned just about as well.

[northmn]

That could be.  I have seen the recomendation about roughing the choke area in more than one place.  This particular shotgun has not been used "dirty" to any extent.  I opened it to about a IC or skeet 1 choke and it shoots pretty tight (also very even)  Where I had trouble loading a round ball it now does fairly easily as well as heavy cards.  Wheter polishing the area would help, I would not say either.  Often the best cure is to shoot the heck out of them.  As it is a flinlock I like a little more open pattern.

DP