Barrel length and velocity?

[zimmerstutzen]

OP, I did not see a caliber reference in your post. The velocity increases for barrel length are most pronounced with calibers between 45 and 50 and both 40 cal and 54 cal caliber have some flukes. A 54 caliber reaches the point where the barrel diameter allows the powder to burn through a given charge so fast that there really isn't a limit on increased fps over a range of powder charges. The point at which a round ball does not increase in velocity as much as lower increments, in a 50 caliber 28 inch barrel seems to generally run between charges of 90 grains to 100 grains. So if you were testing 50 caliber barrels with 80 grains of powder, you may not see much velocity change. The charge is being maximally consumed in all barrel lengths you have. In a 50 caliber, based on the figures in the Lyman Black Powder handbook, 1st edition, I think you would find a difference in your short barrel and the other two when going up to 90 grains and beyond. You really haven't reached the charge where length makes a difference in the barrels you mentioned. Now 80 grains is a right fair hunting charge for most guns here in the eastern woodlands. And many never see a reason to exceed that. For decades, I have used 75 grains in my guns, regardless of the caliber or barrel length.

 

[hanshi]

I've done fairly extensive velocity testing of smokeless arms but a bit less so with BP arms. Modern rifles operate at pressures from 25,000 psi to over 60,000 psi; handguns from 15,000 to around 45,000 psi. BP guns generally range from around 8,000 psi to some 15,000 psi, or thereabouts. BP speeds often rise in fits & starts with occasional losses with added powder.

Many other factors influence velocities in muzzleloaders such as patch thickness, lube, bore condition, etc. These factors often make a greater difference than simply adding more powder. So the question of longer vs shorter barrels for velocities is difficult at best to answer. I think it's nice to know how fast your prb is moving, but it is mostly irrelevant if your load is accurate.

 

[tenngun]

The first rifles had fairly short barrels set on crossbow style stocks. Most jagar rifles tended to be shorter then later American rifles.
Then we see the first war guns also tended to be shorter. With the coming of the bayonet we see longer arms, and longer arms in civilian guns. American rifles could get long.
Stories told that it made the gun shoot harder. I wonder if it was just style, and then the stories followed the style.

 

[Baxter]

I thought that some of the "longer military barrels" on muskets was due, in part, to having the bayonet "stick out further", ie. a desire for a more pike-like length.

 

[tenngun]

I wonder, for I think the same thing. But I wonder if that didn’t inspire longer civilian guns.

 

[brayhaven]

Well, a couple of things. Actually, while people think of black powder as "slow burning " and smokeless as " fast" put a thimble of each in an ashtray and touch them off. The black powder will go up in a blinding flash, while the smokeless will fizzle to and end.

Now, what this means to the discussion at had is this: much as the confusion on high octane gasoline goes, higher octane in fact, burns slower. Sooo, logic tells us that smokeless powder barrels should produce more velocity while black powder, not so much.

BUT!!!!! The burning of the powder charge, is only part of the equation. The principal physics is that an exploding powder charge creates expanding gases, which are what causes the bullet to exit the barrel. So, again the longer the barrel, the more the bullet is going to benefit....UNTIL!!!! The barrel length exceeds the volume of the expanding charge, at which point, the drag of the patch, rifling, ect....begin to scrub off the gains of utilization by the longer barrel.

Sooooo....those are the reasons, and why there aren't any set in stone answers.Now, take the knowledge and apply....

Exactly. Once the expansion of gasses is complete, the acceleration slows and the remaining barrel length can in some instances become drag. In ml or modern guns. With realistic charges there’s not much velocity advantage in long barrels. I made a 42” rifle once, took it to the range and hated the thing. I Took it back to the shop and sawed 6” off and it was fine. Haven’t built a gun with a barrel over 3 feet since. Testing 22 lr ammo for velocity, I found the fastest barrel length was the 10” contender. Faster than rifle length. I once shot a Thompson sub machine gun in Vietnam just to see what it was like. I could watch the bullets going downrange. Later found that the longer barrel slowed them down. Muleskinner.

 

[brayhaven]

Loved Pat McManus, read most of his books. Funny, doesn’t take himself to seriously. Makes you know it is OK to be human, and even the best and brightest of us do ....head up butt, stupid things at times. It may take a spell before we can laugh about it, depending on the screw up, but the sooner you can, the better off you’ll be. It would make a great thread. “What is the worst disastrous screw up you ever made?” I wonder how many would tell the unvarnished truth?

Ahh McManus,, Ed Zern, Havilah Babcock.. et al.. they don’t grow writers like those guys anymore ..

 

[RHensley]

In one of the Lyman reloading books (45 I think) It showed that the T/C haw ken with the 28 in. barrel with round ball with X amount of powder shot X speed at the muzzle. It read that for every 1 in. added to the barrels length and extra X amount of feet per second could be added. Now I use X because I can't remember the exact no. and it could have been one of T/C gun manualsl either way it made since to me. The longer the barrel the more time it gave the powder to burn. I'll try to look it up. Hope I still have the literature. now I am talking about the early 70's

 

[Khufu]

What is the payoff though?
A .40 as tested by Dixie at 1900 FPS and at 2200 FPS will both slow to about 1700 FPS at 25 yards

according to my roundball ballistic calculator a .390 ball launched at 2200 will retain 1759 fps at 25 yards and 1397 fps at 50 yards
while a .390 ball launched at 1900 fps will retain 1509 fps at 25 yards and 1221 fps at 50 yards. that is big enough a difference to be significant.

 

[zimmerstutzen]

according to my roundball ballistic calculator a .390 ball launched at 2200 will retain 1759 fps at 25 yards and 1397 fps at 50 yards
while a .390 ball launched at 1900 fps will retain 1509 fps at 25 yards and 1221 fps at 50 yards. that is big enough a difference to be significant.

A round ball calculator? a 40 caliber ball loses approximately 60% of its velocity at 100 yds. A little more for above the speed of sound, a bit less for sub sonic speeds. Does your calculator take into consideration the increased air resistance at speeds above the speed of sound? That extra 170 fps at 50 yds is not much use unless you are also a very good judge of distance in the field.

 

[tenngun]

Rocky or Thumper won’t notice. A .40 is or was legal in some states for Bambi, but it’s a light gun. I don’t know that extra velocity would make much difference to the sort of shots that would be practically taken.
I like long guns, but know a 32 inch .50 turns deer French just as well as my 42 inch.

 

[Rockvillerich]

Rocky or Thumper won’t notice. A .40 is or was legal in some states for Bambi, but it’s a light gun. I don’t know that extra velocity would make much difference to the sort of shots that would be practically taken.
I like long guns, but know a 32 inch .50 turns deer French just as well as my 42 inch.

I tend to limit my own hunting rifles to 37", which seems to get the job done, and a lot handier in brush. .40 is legal for white tail in Maryland, and since I still get to eat if I come home empty handed, I've relied on shot placement at close range to make clean kills even with moderate loads.

 

[Khufu]

A round ball calculator?

yes it has enough info to give a decent idea of what the ball is doing down range windage is fairly accurate as well.
(ie velocity, energy, drop, wind drift, time of flight.

 

[zimmerstutzen]

That is certainly better than some I have seen.. The PA Game Commission supposedly hired a ballistics expert to calculate how far a shotgun slug would go fired level over level ground. The "X spurt" after consulting his tables found a 12 ga slug would travel some ungodly distance and then said it would bounce another 6 miles. He never fired a shot and his calculator program never even considered air resistance. The factory specs for the round he supposedly tested were far different. Showing a ground strike at half the distance The "Pile Higher Deeper", never even fired a shot but was paid 20 or 30K.

 

[longcruise]

Khufu, which calculator is that?

I found a formula for calculating a round ball BC that gives accurate results using the G1 and G7 tabulations but yours seems to be built in?

 

[Khufu]

Khufu, which calculator is that?

its a freeware one that I got several years ago, it calculates ball weight based on pure lead and is just for round balls from muzzleloaders and shotguns with pumpkin balls. if I can find the url or the original archive with all the freeware warnings I will upload it if you want it.

 

[Khufu]

http://www.ctmuzzleloaders.com/ctml_experiments/rbballistics/rbballistics.html
here is a link to the DL page and the authors description.

 

[longcruise]

Thanks for the link. I'm going to download it and give it some play time.

 

[Zonie]

IMO, that roundball trajectory calculator is a lot of fun to play with if your interested in finding out what your ball (or bullet) is doing.

It will give a rough estimate of what a bullet would do if you just put the bullets weight into that box. Of course, it is just a rough estimate because it is calculating the values based on a slug with a spherical nose and tail on it so the amount of drag on it will be worse than a pointed bullet would actually have.

The calculator is an upgrade of the one I got years ago from the same source.
I have both the old and new versions and the values they calculate are pretty much the same for elevations from sea level up to 1000 feet. The new version gives the option of putting altitude and temperature into the equations.

The thing that will really get your attention with a roundball is the amount of drift a cross wind directly across the balls path. Just a 5 mile an hour gentle breeze can push that ball sideways a lot more than people would imagine it could.

 

[crankshaft]

Yes..the T/C manual listed velocities of several bbl. lengths. They opted for the 28" length as optimum. Longer was better, but the advantage was not worth it, in their opinion.