barrel length to powder charge ratio

[martin9]

I've been ruminating on whether a shorter barrel might be better for shooting light charges and was wondering what others opinion of this is. The reason I'm wondering this is i have 2 28" rice .32 barrels and am wondering if I want to build a halfstock out of one of them or just buy an A weight 44" rice barrel and build a .32 long rifle. I know twist rate is really the deciding factor but besides having a fast twist small caliber barrel made all offerings I know of are 1/48" twist in the smaller calibers.

The reason I'm asking is I'm wanting another small caliber rifle for backyard shooting with light charges. I have 2 .36's already. Going .32 with this build. I thought about ordering a .29 barrel from Burton but am ready to get started on a build and he's at 6 months lead time rightnow.

  Safety is not an issue I have a good bit of land here and no neighbors. I shoot my .62 jaeger with 120 grains of FF regularly in the yard but the light charge/barrel length idea popped into my head so I thought I'd ask.

[Daniel Coats]

I think if it was me I would build up one of the barrels you already have and get that .29 on order. Bonus with the Burton barrel is you can go all the way out to 48" if you wanted. It might depend a bit on your eyes too and what length of barrel gives you the clearest sight picture. I went to an optometrist once with a front and rear sight taped to a broomstick! 

[martin9]

Ha! the broomstick is a good idea. I still have good distance vision....just started needing reading glasses a couple years ago. Ordering the burton barrel is probably the wisest move. I have a stunningly curly halfstock blank from Allen Martin anyway.   

[Daryl]

I went "down" to (started at) 20gr. 3F in my .32 for a starting load. This load, with a .311" Lee mould ball, with a 10 ounce denim patch,
put the first 5 shots into about a .30 calibre hole.  I was ecstatic & immediately went to 50 yards.  That load made a 2" group at 50 yards.
I fired another 5 at 25 yards and they also went into a small hole, this time, about .40 calibre. Back at 50 yards, another 2 to 2 1/2" 5-shot
group. This was a 38" bl. with 48" (most common) twist.
I continued shooting and changing the loads at at 35gr. 3F, I was making 1" to 1 1/2" groups. I could never get that barrel to shoot consistently
better than 1 1/2" at 50 yards and I tried over and over.
If you aren't shooting 40 or 50 yards, or your requirements aren't as stringent as mine, then light loads might work just fine for you. The lighter
the load, the lower the pressure produced, thus less demand on the ball/patch combination, so the looser ball and patch combination you can get
away with, as well.

[martin9]

I appreciate your response, thank you....  I do already know about light loads and would expect the same results. I think my question is hard to word, what I'm wondering is if there is a law of diminishing returns on barrels length...a longer barrel makes better use of the burning powder but at what point does friction from the patched ball traveling down the barrel start to negate that gain.
 
For example I have a 38" and a 42" barreled .36... the 38" barrel groups tighter with lighter loads.

I don't mind loading a .32 up. As I said safety is not an issue, not really interested in powder economy either....especially in such small calibers. Really just an idea I had mulling around in my head and wondered if anyone had any experience or thoughts on it

[Daryl]

Each barrel is unto it's own, as far as how it will shoot, I believe.

Could very well be a 22", 26" or 32" bl. in .32 will outshoot any other length, or exactly the reverse might hold sway.  I do not believe barrel
 length has anything to do with accuracy with lighter charges.
What might though, is the lube used.  A stickier lube, like a water based lube, straight water, or maybe spit will shoot better with a smaller
powder charge, than will a very slippery lube like LHV or Mr. Flintlock's lube. This is likely due to consistency or quality of the powder burning
producing closer shot to shot velocities & pressure, shot to shot at the higher actual pressures, but were inconsistent at lower pressures.
Testing alone will tell, for THAT barrel.
Good shooting also depends on eyes and sight to sight distance.  The longer the barrel, generally the greater distance between the sights and
the the potential for more accurate shooting is the result.  So- where's the tradeoff.?  I'm sure you cannot say:  A 26" bl. will be more accurate than
a 40" bl. will be in .XX calibre with XX powder charge. They have to be tried, to find out.  Ball and patch combinations also have a say in the potential
accuracy in any barrel, no matter the length.

[Jeff Murray]

If you shoot more  powder than the barrel will burn in its length, you shoot the unburned powder out the barrel.  As noted above, the charge, twist, patch and ball combo probably have more impact on accuracy.  I have two 32's, one has a 28 inch barrel with a 1 in 48 twist which shoots 25 grains of 3F very accurately.  The rifle is light and easy to shoot.  I also have a 32 with a 40 inch barrel with a 1 in 66 twist.  I shoot 50 grains of 3f which may seem excessive but that gun is a tack driver with that load and it will take down silhouettes out to 75 yards.  If you are concerned about unburned  powder, put a bed sheet on the ground in front of your muzzle and check out the debris that comes out of the barrel.  Or in a pinch, just shoot what works. 

[smylee grouch]

The bed sheet or snow idea can fool some people as the debris coming out of the barrel might be fouling and not unburned powder. This told to me by someone who is a Real expert in this field. I was also told that in most cases black powder flashes and is burned up before it reaches half way down the barrel. I suppose you could collect the debris on the bed sheet and try to burn it to find out first hand. When I teach Hunter Ed. class I do a demo by burning a tablespoon of H870 smokeless powder and then a tablespoon of 2f black powder to show the burn difference's. This really shows the difference between the two as the H870 takes a couple of seconds to burn and the Black flashes in an instant. I show the students that even though the H870 is Black in color it is not BLACK POWDER.

[Levy]

At the last Knoxville Show, I purchased a Rice kid's barrel that was 31" in length, swamped and had a rate of twist in the low 30's if I remember correctly.  Actually, I've purchased two of them, but don't remember what the twist was in the first one, which was purchased a year or two before.  James Levy

[Daryl]

The bed sheet or snow idea can fool some people as the debris coming out of the barrel might be fouling and not unburned powder. This told to me by someone who is a Real expert in this field. I was also told that in most cases black powder flashes and is burned up before it reaches half way down the barrel. I suppose you could collect the debris on the bed sheet and try to burn it to find out first hand. When I teach Hunter Ed. class I do a demo by burning a tablespoon of H870 smokeless powder and then a tablespoon of 2f black powder to show the burn difference's. This really shows the difference between the two as the H870 takes a couple of seconds to burn and the Black flashes in an instant. I show the students that even though the H870 is Black in color it is not BLACK POWDER.

Smylee hits the nail on the head. I am most convinced, that all of the black powder is burning inside the barrel, and quite close to the breech. What you see as sparks, if simply glowing 'debris', ie: charcoal and super hot particulate fouling.  I have seen numbers at around of 57% of a black powder charge burned, is solid waste. some of this is blown free, some is deposited on the bore's wallsas fouling.

[martin9]

Levy, thanks for the tip...heading over to Rices' site now.

[Mad Monk]

The bed sheet or snow idea can fool some people as the debris coming out of the barrel might be fouling and not unburned powder. This told to me by someone who is a Real expert in this field. I was also told that in most cases black powder flashes and is burned up before it reaches half way down the barrel. I suppose you could collect the debris on the bed sheet and try to burn it to find out first hand. When I teach Hunter Ed. class I do a demo by burning a tablespoon of H870 smokeless powder and then a tablespoon of 2f black powder to show the burn difference's. This really shows the difference between the two as the H870 takes a couple of seconds to burn and the Black flashes in an instant. I show the students that even though the H870 is Black in color it is not BLACK POWDER.

Smylee hits the nail on the head. I am most convinced, that all of the black powder is burning inside the barrel, and quite close to the breech. What you see as sparks, if simply glowing 'debris', ie: charcoal and super hot particulate fouling.  I have seen numbers at around of 57% of a black powder charge burned, is solid waste. some of this is blown free, some is deposited on the bore's wallsas fouling.

Daryl,

You are quite correct in stating that every bit of powder is burned in a short distance in the barrel.  With a charge of 3F that distance is about 3 to 4 inches of ball travel.  With 2F that would go up to around 6 inches.  When you have fine grain black powder in the bore and ignite the charge the flamespread rate up through the charge can approach 2200 fps.  The general publications state that about 55% of the weight of the original charge will end up as solid products of combustion versus gases.  There will be some variation in that combustion depending on how the powder was formulated.  With the Swiss and their 78 parts of potassium nitrate versus 75 for other powders you actually get a little more conversion.  But mainly the amount of available oxygen from the powder will change the ratio of carbon dioxide and carbon monoxide in the combustion gases.

That thing about shooting over a sheet is now grossly not understood.  When you go back into the 1800s they were usually hotting what might be called a mixture of today's grain sizes.  Some of the old powder samples I had looked at sometimes contained a few percent of a rather large grain size.  Most of the real sporting powders were something of an equal mixture of the 2f and 3f grain sizes.  In my lab I had a whole big pile of standard screens that I used on PVC suspension resins.  When the boss wasn't looking I would throw 100 gams of a sample powder into the stack and record the range of grain sizes in the sample.  Then compare these results to the standard screen sizes that the U.S. powder industry adapted around 1838 when the industry standardized.  But, and a big but here, not all of the powder manufacturers went to the standard sizes.  Then they were faced with large customers who wanted their own grain size range in a powder.

When I was doing my work on how the powder combustion residue was deposited in various sections of the bore I found that most of the fouling was retained back in the bore for the distance it took to burn the powder.  And what was between that area and the muzzle was variable but a lot less.  Then I set up to shoot through a funnel  With a big piece of lab filter paper taped in place.  Then the solid stuff in the smoke clung to it.  And I could run a pH on them and look at them under the computer microscope.  The so called "smoke" proved to be very minute particles of potassium carbonate and potassium sulfate.  With no burn spots indicating that any partially burned powder or slowly burning charcoal was being ejected in the gases leaving the muzzle.

Bill K.

[smylee grouch]

Hi Bill. I think I read that before someplace. I,m glad to see you still participating as you input truly bring this subject expertise. thanks for the response. 

[Mad Monk]

Hi Bill. I think I read that before someplace. I,m glad to see you still participating as you input truly bring this subject expertise. thanks for the response. 

Wen I first saw this thread it took me back to my old Lyman Black Powder Handbook that had been sold back around 1975 or 1976.  My copy literally fell apart from use and the paper was getting brittle.  They did a wealth of shooting where they were comparing powder charges in different barrel lengths in the same caliber.  Looking at how with a specific charge the velocities changed with barrel lengths.  On in the smaller calibers in real long barrels did they see a point where barrel length actually takes away velocity seen in shorter barrels.  But then with a bit of work their ballistic data was something of a gold mine of information.  Around that time I was looking at a pile of PA flintlock deer hunters who were cutting down T/C barrels to make them "more handy in brush".  You had to see some of the places we hunted in flintlock season.  If you want to see a new meaning to frustration try to hunt deer in a steep mountainside completely covered in huge Mountain Laurel bushes. You could hear them walking around the other side of the bush snorting as they were smelling you.  But no way could you get even a glimpse of one to get a shot off.  Oh. The T/C Hawken owners found that they did not much of a velocity loss until they cut the barrels shorter than 18 inches.  And a lot of good that did them in heavy laurel on a mountainside!!!

Back to this barrel length thing.  The idea is that you can continue to accelerate the ball as long as you have sufficient pressure behind the ball.  But that when the pressure in the barrel falls below you get no increase in muzzle velocity.  And if the barrel is long enough for a really serious drop in pressure you will find the muzzle velocity actually dropping.

Bill K.

[buck conner]

It might depend a bit on your eyes too and what length of barrel gives you the clearest sight picture. I went to an optometrist once with a front and rear sight taped to a broomstick!

/
My optometrist is a shooter, has a slim full stock with a dowel barrel and traditional sights mounted for those of us wanting a better vision down range.  Said he has made several of these stock setup for fellow classmates in the same business.
.

[Mad Monk]

Another round of sitting and thinking back a bunch of years.  Going back to the 1980's.  Here in a we had a large number of flintlocks shooters out in the field for the after Christmas primitive weapons deer hunt.  So shooters were wanting shorter barrels for their T/C Hawken rifles claimed to be handier in the brush. So we saw a lot of those guns have their barrels cut down.  Then of course there were questions on what would be ideal.  Most of what was being claimed at the time was 18" was the shortest you cut cut those barrels before you start cutting down in muzzle velocities.  I seem to remember 18" being considered to be the shortest you want to go before you start to loose a lot of velocity.  Then all of a sudden you saw and heard nothing more on that subject.

[Ghillie]

I have a .32 caliber rifle I built in 1972 with a 1-66 twist Douglass barrel.  It shoots great with whatever charge you want to use.  I used 30 grains in the 25 and 50 yard matches and 60 grains in the 100 yard matches.  My first  1st place club ribbon was with this gun, 60 grains at 100 yards.  I killed a groundhog at 125 yards using @ 70 grains of powder.  Dead right there  DRT.  My gun has a 38 inch barrel.  Doesn't seem to care what powder charge I use.

[rollingblock]

kinda off on a different tangent but would barrel pin or wedge placement make a difference in where the ball hits. I'm thinking I read sometime ago about barrel harmonics, free floating barrels. definitely barrel length (sight radius) makes a difference in my old eyes.

[Daniel Coats]

Yep old eyes need the rear sight moved out closer to the target. 

[Mad Monk]

Yep old eyes need the rear sight moved out closer to the target. 

This one has me laughing as an aging hooter who went through that.  Then I remember the one schimmel in Dixon's collection where the rear sight had been moved 4 times and ended up sitting just  behind the entry thimble.
 

[Daryl]

kinda off on a different tangent but would barrel pin or wedge placement make a difference in where the ball hits. I'm thinking I read sometime ago about barrel harmonics, free floating barrels. definitely barrel length (sight radius) makes a difference in my old eyes.

Gun makeup/style/weight/barrel size and shape/everything goes into barrel harmonics. This is why we try a bunch of different components searching for the best combination.
There are no hard and fast rules, except we've found a 10 ounce denim patch, which I measure at .021" and a ball .005" under the bore size, is a good place to start. You could start
with a powder charge 5gr. over bore size would be a good place, ie: 50gr. in a .45, 45gr. in a .40, etc. For ctg. smaller than .40, I'd start at bore size in grains.  For calibres .50 and over,
then 10gr. over bore size would be a good starting place. I use 3F up to and including .45-  usually and 2F in calibres larger than 50.
It's a starting place only.
It usually takes more powder to get good accuracy at longer ranges, that is, the longer the range, the more powder is needed to produce the best accuracy.