Why Are BP Rifle Barrels So Thick And Heavy?

[Cosmoline]

I must be missing something. Given that BP powder generates far less pressure than smokeless, why are BP rifle barrels so much more massive than even very high powered smokeless rifle barrels? The walls tend to be extremely thick and the chambers massive. Even though the end result wouldn't even reach the level of a low charge .45-70. Is all that steel really necessary? Or is it just a tradition going back to iron barrels?

Coupled with this, I've seen many BP shotgun fowler barrels that are very thin walled. Is there that much pressure difference between rifle and smoothbore?

 

[4v50 Gary]

I'm leaning toward tradition. When you look a British Baker rifle, the barrel isn't thick like the more common octagon barrels are.

 

[arcticap]

I have a rifled Pedersoli .50 octagon that's only 13/16th's between the flats. Yet many .50 BP barrels are often 1 inch octagon.
So I agree that it's more traditional rather than necessary.
And the heavier barrel may also help to dampen the recoil and to keep the barrel steadier for target shooting with the relatively slower locks.
The chunk gun target rifles have some the the heaviest and thickest barrels for longer range precision shooting. The extra thickness must also help to keep the barrel cooler, more rigid and accurate during competitive shooting.

 

[ThomasT]

When original barrels were made they were made from flat iron that was heated and welded around a mandril. The iron was softer than modern steels and needed to be thicker. I am guessing thicker was easier to weld also. Plus a thicker barrel allowed for refreshening the bore later on.

Steel barrels can be made thinner and the barrels we have now are thinner than barrels from the early 1800s. I have got to handle a couple original guns and those dudes were heavy. Like 12+ pounds for a 50 caliber rifle.

 

[Mike OTDP]

Balance...and if you look at a long rifle, the barrel is a structural component. The stock would easily break in half without it.

 

[Cosmoline]

I have a Pedersoli .50 octagon that's only 13/16th's between the flats. Yet many .50 BP barrels are often 1 inch octagon.

I've got a .54 smooth rifle that's 13/16 between the flats and have had all kinds of dire warnings about how it's dangerous--though nobody seems to be able to articulate why it's so dangerous. I've limited it to shot for the time being, but I'm very skeptical about the actual need for massive chambers on a modern steel BP barrel. How much actual PSI is 90 grains of FFG going to generate?

 

[Oyeboten]

Shotguns have such thin Barrels relatively...even if of course they taper to be thicker toward the Breech.

This always puzzled me also.

Similarly, how thin the Steel is on the periphery of Revolver Cylinders, relative to how thick the Revolver Barrel.

Blance, Style, form, Tradition for these, old deferences to Wrought Iron...all combine I s'pose...

 

[arcticap]

There's an interesting thread on the related subject of .54 rifled barrels and velocities which compares ffg vs. fffg from a variety of .54 rifles over on the Muzzle Loading Forum.

Evidently the Lyman 2nd Edition lists fffg as producing less velocity than ffg does from a 32" .54 rifle which one member set out to disprove. And that was the opposite of what Lyman listed for the 24" and 28" .54 barrel velocities. From one .54 barrel, the poster obtained equal results using both powders and with another longer barrel he obtained much higher velocities using fffg.

From all similar .54 caliber chronographing I've done, here are the charges, number of shots, mean velocity and extreme velocity spread. First, with Goex 3F:
80 grains, 74 shots, mean 1615 fps, ES 61 fps
90 gr, 41 shots, M 1676, ES 69
100 gr, 21 shots, M 1745, ES 87
110 gr, 9 shots, M 1850, ES 120
120 gr, 11 shots, M 1871, ES 92
120 gr, 14 shots, M 1957, ES 128( my Leman, which has a tighter bore)

With Goex 2F:
80 gr, 16 shots, M 1398, ES 55
90 gr, 5 shots, M 1515, ES 59
100 gr, 5 shots, M 1577, ES 63
110 gr, 5 shots, M 1591, ES 21
120 gr, 18 shots, M 1685, ES 46
120 gr, 22 shots, M 1868, ES 64 (4 rifles 4-13 years ago)
120 gr, 10 shots, M 1783, ES 59 (Moosic, PA powder, my 200 yard test with scoped Hawken)
120 gr, 9 shots, M 1879, ES 104 (my Leman)

In my testing, the Goex 3F produced more velocity than the Goex 2F. I have no way to compare pressure. I have no explanation or guess for Lyman's results with these powders in the .54.

Of course these results are dependent on the barrel, the barrel length, the specific brand of powder, the load and even the patches.
But the point is that most folks regularly use ffg when they could use fffg and simply reduce their loads by at least 10-15% to keep the pressures similar.

Also mentioned in the thread was that the TC Owner's Manual does not list loads using fffg for their .54.

Another poster mentioned:

By contrast, our large bore muzzleloaders operate way down low in the 7,000-10,000 PSI range...AND...when 3F charges are used in place of 2F, the quantiy is reduced to keep pressures in the same ballpark as 2F would be operating.

I don't have the Lyman Handbook but this report illustrates that every barrel is different and even test results can vary. But generally a modern barrel made from modern gun steel by a reputable maker that's in good condition should be safe to shoot with 100 grains of ffg powder if not full charges.

I have a thin walled .28 gauge Spanish made smoothbore (.54 - .55) with a modified choke, and I've shot very large shot loads from it loaded with ~100 grains of Pyrodex RS, and only moderate loads with .520 patched round balls because accuracy suffers due to the choke. But for comparison the patched ball weighs almost 50% less than 1 ounce of shot does so it could be loaded using just as much powder.

Free registration is required to view the Muzzle Loading Forum thread. Just follow my personal referral link to register:

http://www.muzzleloadingforum.com/fusionbb/index.php?referral/4225/


Here's the thread posted by long time MLF member Herb:

http://www.muzzleloadingforum.com/fusionbb/showtopic.php?tid/228706

 

[ThomasT]

One thing to watch when using the Lyman manual is to make sure you are looking at Goex data. My manual also has data for Curtis & Harvey (C&H) powder and it is weaker or slower burning and takes a larger amount to equal Goex powder.

 

[StrawHat]

Cosmoline

I must be missing something. Given that BP powder generates far less pressure than smokeless, why are BP rifle barrels so much more massive than even very high powered smokeless rifle barrels? The walls tend to be extremely thick and the chambers massive. Even though the end result wouldn't even reach the level of a low charge .45-70. Is all that steel really necessary? Or is it just a tradition going back to iron barrels?

Coupled with this, I've seen many BP shotgun fowler barrels that are very thin walled. Is there that much pressure difference between rifle and smoothbore?

The heavy thick barrels and firearms are an American adaption of an idea. English rifles tend to be lighter and better balanced. Not sure why we went heavy this side of the pond but we did. It is only recently that lightweight rifles have caught on.

 

[denster]

Cosmoline: Your 54Cal X13/16 should be safe with reasonable patched round ball loads. You still have .093 sidewall thickness with a 5/8 breechplug and .230 wall thickness at the bore which is adequate for a 1/4X28 drum or liner depending if you have flint or percussion. Presuming of course that both plug and drum/liner are well fit.

 

[rugbyer81]

I think part of it had to do with prolonging the life of the barrel when proper cleaning wasn't always available. Re-boring to a larger calibre would be possible with an extra thick barrel and would be a lot easier and cheaper for a frontier gunsmith to do then provide an new barrel. I found this on Wikipedia:



"To conserve lead on the frontier, smaller calibers were often preferred, ranging often from about .36 to .45 cal. Such were commonly used for hunting squirrels and other small game, as well as for hunting deer. As a rifle became extensively more and more worn from use, with accumulated corrosion from firing blackpowder causing the bore to enlarge, it was not uncommon to see many such individual rifles being re-bored and re-rifled at larger calibers, to keep the rifle shooting accurately. Many extant copies of historical Kentucky Rifles are seen with a bore of around .50 caliber, having been the last caliber to which the barrel had been bored and rifled."

 

[Oyeboten]

With the Wrought and Forge Welded Iron of those 'early' days Barrels, I imagine having the Barrel on the hefty side, also made it less likely to get bent in mishap than if it were made thinner.

Thinner would have been fine for the Pressures of the Charges for the Caliber, even for .50-odd Calibre ( which was still Gauge then), but, trip and fall on it in the Brush or Woods, and it mighta bent...