Powder charge question/barrel lenght

[jafo20]

Hello,

I was wondering if anyone can tell me what lenght a 50cal. Barrel has to be to burn a 100gr. Powder charge? How many inches of barrel do you think it takes to burn the entire charge?

Thanks

[rich pierce]

The old Lyman book has a lot of choronograph figures for barrels of different lengths.  In general, the charge gets burned, but barrel length influences velocity as the pressure has more time to act on the projectile. Another way of asking the question is: at what length does 100 grains of powder get me a significant increase in velocity over 80 grains, or 90 grains?  I would guess you need 30" or more to get a 5% velocity increase with a 10% charge increase, going from 90 to 100 grains.

[jafo20]

Thanks.....so below 30"  and performance is going down hill?

[BrownBear]

Thanks.....so below 30"  and performance is going down hill?

It's a tradeoff.  If I was intent on conserving powder, I'd be using nothing but 48" and longer barrels.  But I have other measures for gun "efficiency" that are more important to me.  There are situations and settings I have to contend with that call for barrels shorter than 30.  Darn the powder efficiency torpedoes and full speed ahead.  I go shorter when it suits me.

My shortest rifle is a 24" barreled 58 cal.  I have no clue how fast it's launching a ball on top of 100 grains of powder, and don't care.  It works for my needs.  Of course that little sucker is so loud my hunting pardners have named it DANG!!!.  They'd rather not be on hand when I bring it to the range.  But they're more than happy to have me along to drag it into deep alder tangles when the deer dig deep, just so they get a share of venison.

[Dphariss]

Thanks.....so below 30"  and performance is going down hill?

Burn it or use it efficiently? The longer barrel, within reason, will ALWAYS get more from a given charge of BP unless its a very small charge.
Performance would likely suffer with 50 grains comparing a 30" barrel to a 36-40" barrel. But will it significantly reduce effectiveness of a given load? Probably not unless the barrel is under 24-26". But small bores like a 50 do not use the powder as efficiently as a 67-69 caliber will and will do better with longer barrels.
A look at American ML rifles of the 18th and 19th century will show that few are under 32" or so and most will be 36" more or less in the 1840s-60s. Earlier rifles will generally have barrels approaching 4 ft but this is not 100% correct there were short rifles in Colonial times.
What the barrel likes as an accuracy load is the important point.
Generally 90 gr of FFF is all that is needed in any 50 caliber  to gain a good trajectory.
This is the point of a high velocity load, a flat trajectory. It is very difficult to increase killing power of a lead RB with velocity past 30 yards or so unless comparing a very light load to a very heavy one.
Then at close range the HV load may not penetrate as well as a moderate velocity load. This is true of any soft bullet that will deform easily on impact.
IMO rifles with barrels under 30" are too short unless building an English Big Game rifle and these are invariably larger than 16 to the pound and will use the powder more efficiently in the shorter barrel. Some German jaegers were very short as well. But they were not HV rifles.
Dan

[Daryl]

My 24" Musketoon produces 1,308fps with a .562" round ball & 75gr. 2f GOEX.  The bore is .574" instead of .577" or .580"- It's a tight one.  Lyman's book gives barely over 1,000fps for this load range.   Their .58 data seems a bit strange, as to velocities per barrel length - they don't jive properly as the shorter barrels give higher speeds for any given charge weight.  It is quite posible their numbers are switched, however, it is true, that this small charge deveoped over 1,300fps in 24".  It seems efficient.

[Herb]

Lyman's "Black Powder Handbook & Loading Manual", 2nd edition:  With .490 roundballs and Goex Powder:  24" barrel 1 in 48" twist, 100 grains of 2F gave 1622 fps and 3F gave 1757 fps.  A 28" 1-48 twist barrel, 2F gave 1729 and 3F was 1911 fps.  A 32" 1-60" twist barrel, 1848 and 1949 fps.  With 120 grains of powder, 24" was 1792 and 1830 fps.  28" was 1806 and 2015 fps.  32" was 1991 and 2045 fps.

[Daryl]

I tested a 22" bl. in .50 cal and with 80gr. 3F, I recorded 1,760fps - .495" ball and .0225", 10oz denim patch using LHV for lube. This was with 3 F GOEX I'd purchased 4 years ago.

Lyman's data seems to hold right for the other calibres, but not for .58's.  In the .58, only 2F was used and only the quite undersized .562" balls. Consider Lyman use various lengths of Zouave barrels in .58 cal. along with .020" (or .022") patches,  the .003" depth grooves handles them quite well.

Interesting comparrison, Herb.
I read the .50 cal. data thusly because I have trouble with it all in a straight line.
:24" - 100gr. 2F - 1,622fps -------3F --------- 1,757fps
:28" - 100gr. 2F - 1,729fps -------3F --------- 1,911fps
:32" w/60 tw. - 100gr. 2F - 1,848fps -3F---- 1,949fps

:24" - 120gr. 2F - 1,792----------3F-------1,830fps
:28" - 120gr. 2F - 1,806----------3F-------2,015fps
:32" - 120gr. 2F - 1,991----------3F-------2,045fps

:24" jumped 170fps with + 20gr. 2F and only 73 fps with + 20gr. of 3F.
:28" jumped 77fps with + 20gr. 2F and 104fps with + 20gr. of 3F
:32" jumped 143fps with + 20gr. 2F and 96fps with +20gr. 3F.

With the 120gr. charge, a charge some would say was inefficient in a short barrel, the 28" was faster than the 24" by 14fps. only using 2F and 185fps using 3F. The 32" beat the 28" by 185fps using 2f and 30fps using 3F.

Of note - the 170fps jump with an increase of 20gr. of 2F in the shortest barrel and 143fps jump, the second highest increase, in the longest barrel, again with 2F.  Some recordied velocities are amazingly close. 

The biggest differences ie: velocity jumps between the barrel lengths are between 28" and 24" using 3F and between 32" and 28" using 2F.

 "Is that wierd or what?"

[Daryl]

From that I'd say the 24" barrel burned up to 120gr. of both 2f and 3F quite well. Our powder is different than that used back in the late 60's or early 70's when Lyman did all that testing. The powder is different, but the trends should follow.

Use as much powder as is necessary to achieve the ballistics you desire. With a good ball and patch combination, the more powder you put in, the more accurate it will be and the flatter shooting it will be.  If you lose accuracy with additional powder, even in a 48" twist, the ball and patch combination is in need of attention.  I'd say that 120gr. 2F is within reason in a 28" bl.

I prefer 2F in calibres .50 and above as I've found it more accurate overall as well as being less stressful on the ball and patch combination than 3F. According to LYman's data, 100gr. of 3F gives close to the same velocity as 120gr. of 2F- only 35fps difference. Of course, those velocities will be incorrect today as the powder is different. One really needs a chronograph to know for sure.

[Herb]

Thanks for displaying that material in a manner easier to compare.  This data came from the 2nd edition, copyright 2001, not the first edition where the powder was different.  So the velocities should be what we get with powder we now buy, and in fact my chronographing usually agrees pretty closely with Lyman's data.

[Dphariss]

The problem with Lyman's data is that the powder they were using was probably not consistent from pound to pound much less case to case. Heck it may have varied in the same pound of powder.
This screws up everything.
I never trusted the pressure data. A load with a conical that supposedly would make the same pressure would eat nipples in 15-20 shots when the RB load would shoot for long periods with no pressure signs.
It could have been a longer pressure curve I suppose but the data in many cases just made no sense.
Dan

[Daryl]

Thanks for displaying that material in a manner easier to compare.  This data came from the 2nd edition, copyright 2001, not the first edition where the powder was different.  So the velocities should be what we get with powder we now buy, and in fact my chronographing usually agrees pretty closely with Lyman's data.

Will have to look around for that 2001 edition.

[Dave Faletti]

Does the newer Lyman book mention when they did the testing? Newer book doesn't guarantee new data but I would hope it is in the same timeframe.

[Herb]

The data in this edition is new testing.  For "Powders" they explained "We attempted to use the most commonly available powders.  These were Elephant Brand and Goex black powder and Pyrodex RS, Select, P, and Pellets.....Goex Clear Shot, a new black powder substitute, was also used, although data is limited as it became available late in out testing."

[Daryl]

That sounds great. I wonder if googling it will bring up a copy online? well , did it, lots of places in the States - I googled Lyman Black Powder Handbook 2nd