How long does a barrel need to be to be efficient?

[muskeg13]

Sorry if this question has been discussed before, but how long does a barrel need to be to be efficient for BP cartridge shooting? I know it depends on bore size and how much powder is to be consumed, but bear with me. Both sporting and military BP cartridge barrels were commonly 30 inches to as long as 34 or more inches, but I suspect extremely long barrel lengths weren't needed for powder burn efficiency as much as to obtain a long sight radius, dampen recoil, and serve as a pike when a bayonet was mounted.

The Trapdoor M1873 Springfield was offered in 3 nominal barrel lengths, a 22" carbine, a 26" "Officer's Model", and the standard infantry version with about a 32 inch barrel. How efficient were the two shorter versions with the standard full power service cartridge with either a 405 or 500 grain bullet over 70 grains of 1f or 2F black powder?

I'm planning a .50-70 project and haven't determined how long I want the barrel to be. I have rifles in my gun safe with barrels as long as 37" and find them a bit unwieldy. I'm considering building a carbine or short rifle with a barrel between 22-26 inches, using "real" FFg black powder and a Lyman 515141 (~425 grains) as a standard load. Would the shorter barrel lengths allow for efficient burning of a full case of BP? How about with Pyrodex or Hodgdon 777 2F?

[Nobade]

After owning Argentine rolling block carbine and rifles, my take on it is the rifle is only slightly more powerful but considerably easier to shoot because of the longer sight radius, much less muzzle blast, and more stable to hold. If I were doing what you are doing, I would go for what feels best to me for carrying and shooting, and not worry about the ballistics too much. Depending on what action you use, I would suspect somewhere between 28 and 32 inches will feel the best and give plenty of power. If it's a Trapdoor, maybe a bit shorter due to the longer action.

[muskeg13]

The action will be a Swedish rolling block.

[Bigslug]

+1 with Nobade.

The .50-70 will be burning not all that much fast-burning powder in a positively HYUUUUUUUUUGE bore volume. Much like with the .45ACP, you're going to generate your peak pressure pretty quickly, and that pressure - and its ability to accelerate a bullet - will drop off precipitously as the bore volume behind the bullet increases.

Having some experience with the cartridge, even with the longer barrels, it's basically a mortar that gives you almost enough time on a 100 yard target to say "waaaaaait for it" between ignition and impact. I too would be looking at issues of carry comfort, swing, and sight radius as my priorities. As far as flight characteristics go, any way you slice it, the .50-70 is a penguin.:mrgreen:

[BLAHUT]

Depends on what you are going to use it for, general shooting and hunting or long-range competition, for long range competition I would go with the longest barrel you can get, for the sight radius, reduces recoil, makes for a steadier shot... You can always cut a longer barrel down, should you want... IMHO

[muskeg13]

I plan to use the carbine/short rifle for casual shooting and possibly hunting, mostly at 100 yds or less, but not to exceed 300 yards.
Does anyone have experience with a .50-70 carbine? I believe they usually have 22" barrels. I suppose there's no issue with BP or substitutes being completely consumed, but how bad is the muzzle blast?

A related question is, does anyone shoot a Trapdoor Officer's Model with a 26" barrel, and what are your observations with this length barrel with BP or BP substitutes?

[John in PA]

The federal government actually studied this at the national armory in 1875. They varied powder charges and barrel lengths to extremes in both directions. A copy of the original hand written chart showing the results of the experiments is available. I got one, laminated it, and hung it on the wall of my gun room.

https://www.chamberit.com/collections/historic-ammunition-cartridges/products/45-70-government-project-of-experiments-poster

Description: The 45-70 Govt. Project of Experiments poster is a unique replica of the actual hand sketched report of the project of experiments conducted at the National Armory (Springfield, MA) and drafted in March of 1875. This chart displays the various experiments conducted using the .45 caliber bullet weighing between 200 grains and 800 grains, with powder charges between 10 grains and 140 grains, and barrel lengths between 1 inch and 120 inches!! The test results show that the .45 caliber cartridge loaded with 70 grains of black powder and a bullet weight of 405 grains was the optimal choice for the service cartridge in the 32-5/8” barreled model 1873 trapdoor Springfield rifle.

The findings of these experiments confirmed the validity and utility of the 45-70-405 (45-70 Government) as a viable infantry cartridge capable of volley fire well beyond that era's accepted limit of effective range.
(NOTE: These experiments were conducted with the 405 gr arsenal bullet. In 1881 the arsenal determined that the 500 grain bullet actually maintained a flatter trajectory at long range. The new ammunition was adopted, and Trapdoor Springfield *rifles* made in later years have their sights calibrated for use with that bullet. The carbines remained regulated for .45-55-405 carbine ammunition throughout production)

[Dave T]

Great info John. Thanks for posting it.

Dave

[muskeg13]

Great info John. Thanks for posting it.
Dave

Ditto. It would be nice if this site provided for "likes."

Also, I began re-reading Mike Venturino's "Shooting Buffalo Rifles of the Old West," and it seems Remington's standard model sporting rolling block came with a 26" barrel.

[freakonaleash]

I have 3 antique marlin lever guns with 24 inch barrels. Lube starvation isn't much of a problem like it is for 28 inch plus barrels. Open sight accuracy is about 100 yards for me no matter what I'm shooting so sight radius isn't an issue for me either. Also a very handy hunting gun length.

[hiram]

I had a roller built. I used a Douglas 28" barrel. If you take the time to work up a load, you should do fine.

[Abert Rim]

John Taylor barreled and chambered a Husqvarna rolling block action with a 30-inch Green Mountain straight taper barrel for me. Using walnut from George at Treebone fitted by Tim Rossbach and with steel buttplate, the rifle was tolerable to shoot from the bench with loads of OE FFg compressed under the Lee 515-450 boolit. When I stepped it up with the 600-grain .510 Creedmoor from Buffalo Arms, the rifle became unpleasant after a few rounds without a shoulder pad. There is an assumption made by some that the .50-70 was a "weak sister" compared to its successor, the .45-70. To use a phrase that Mike Venturino favors: "Not hardly!"

[indian joe]

John Taylor barreled and chambered a Husqvarna rolling block action with a 30-inch Green Mountain straight taper barrel for me. Using walnut from George at Treebone fitted by Tim Rossbach and with steel buttplate, the rifle was tolerable to shoot from the bench with loads of OE FFg compressed under the Lee 515-450 boolit. When I stepped it up with the 600-grain .510 Creedmoor from Buffalo Arms, the rifle became unpleasant after a few rounds without a shoulder pad. There is an assumption made by some that the .50-70 was a "weak sister" compared to its successor, the .45-70. To use a phrase that Mike Venturino favors: "Not hardly!"

30 inch is a nice balance for a single shot action, cartridge rifle - take it out to 34 inch and your fouling management needs to be much better.

[muskeg13]

I got my barrel in the mail yesterday from Kenn Womack at http://www.rollingblockparts.com/ It's off of a Swedish M1867 that was cut back from 37.25 to 30 inches. I had thoughts to cut it back even further to 28 or even 26 inches, but when I screwed it into the receiver, it almost balances (w/o the buttstock), and it's not that heavy. So, I'm going to finish crowning it and give it a go at 30" for a while. I can always trim it back shorter later.

For kicks, I tried inserting an unfired Starline .50-70 to see how far the case would go into the chamber. Surprisingly, it easily went in almost to the rim. I full length sized the case and it went in up to the rim like it was chambered for it. I only need to open the rim recess a few thousandths to be able to use Starline cases. The barrel slugged at .510 with deep sharp grooves.

[country gent]

Efficiency is affected by many things case design, bullet weight length bearing surface, powder burn rates and pressure range.

Case design. cases like the older calibers with lots of body taper and gradual shoulders arnt as efficient as some of the newer designs with shallow body tapers and sharper shoulders. Some of the new case designs burn most of the powder inside the case.

A heavy bullet with longer bearing length provides more resistance promoting more complete burns and better consistency. These bullets start off slower keeping the burn contained in a smaller area.

A too slow powder burning at under pressure levels will leave unburned powder in the bores and inconsistent results. a to fast powder burns quickly but dosnt provide the real push needed.

[indian joe]

Efficiency is affected by many things case design, bullet weight length bearing surface, powder burn rates and pressure range.

Case design. cases like the older calibers with lots of body taper and gradual shoulders arnt as efficient as some of the newer designs with shallow body tapers and sharper shoulders. Some of the new case designs burn most of the powder inside the case.

A heavy bullet with longer bearing length provides more resistance promoting more complete burns and better consistency. These bullets start off slower keeping the burn contained in a smaller area.

A too slow powder burning at under pressure levels will leave unburned powder in the bores and inconsistent results. a to fast powder burns quickly but dosnt provide the real push needed.

wasnt this question about blackpowder ?

[Sgt H]

Probably doesn't mean much but sometime back I read a test report on 45-70 barrel length effect on velocity. I recall the test was with a heavy smokeless load that drove a 400 grain jacketed bullet at 1900+ fps. They started with a long barrel and cut it down an inch at a time. In the test the velocity peaked at 25-26" and was slightly slower above this. The velocity at 18" was only about 100 fps slower than 26". The bore volume/expansion ratio on the 45-70 and other big bores is such that the pressure drops very rapidly as the bullet moves down the barrel.

[muskeg13]

wasnt this question about blackpowder ?

Yes, my concern was with efficiency with black powder and BP substitutes, particularly Pyrodex and Hodgdon 777 in a .50-70. The baseline load would be a 425/450 gr Lyman Ideal 515141 with 70gr of FFg. From further research and posts here, it seems that 26-30 inches is the optimum, and I'd give up about 200-250 fps in a 22 inch carbine barrel. I'd also guess I'd actually lose a little velocity by shooting the baseline load in a 37+ inch Swedish RB barrel.

[indian joe]

Yes, my concern was with efficiency with black powder and BP substitutes, particularly Pyrodex and Hodgdon 777 in a .50-70. The baseline load would be a 425/450 gr Lyman Ideal 515141 with 70gr of FFg. From further research and posts here, it seems that 26-30 inches is the optimum, and I'd give up about 200-250 fps in a 22 inch carbine barrel. I'd also guess I'd actually lose a little velocity by shooting the baseline load in a 37+ inch Swedish RB barrel.

I have nothing to back my opinion but I believe the grade of powder would make more than a little difference - Fg likely take full advantage of the extra barrel length - some old feller told me once that each G was worth about six inches of barrel (dont remember who he was or where) it kinda made sense
I know nothing of substitutes - bought a can of pyrodex one time - fired a few shots and sold it to a bloke I didnt like.........................

[Good Cheer]

Look to the bottle necked black powder target cartridges of yesteryear.

[RyanJames170]

I have nothing to back my opinion but I believe the grade of powder would make more than a little difference - Fg likely take full advantage of the extra barrel length - some old feller told me once that each G was worth about six inches of barrel (dont remember who he was or where) it kinda made sense
I know nothing of substitutes - bought a can of pyrodex one time - fired a few shots and sold it to a bloke I didnt like.........................

I could agree that that might be true, it would be a interesting thing to actually test

[perotter]

To be efficient 24" would be good for being efficicient. One of 20" is a bit short for getting range. Based on historical data and use.

The question is efficient and not optimized length.

One historical point of practical use was the Westley Richards used by the Boers. They found 24" barrels the best overall. Good enough to to cause a up to a 40 to 1 kill ratio against the British army in the 1st Boer War. The Brits had long barrelled Martini-Henry's.

In the last battle the Boers killed 92 Brits with 78 of the kills being head shots. So the 24" barrel proved to be both accurate and provide enough power to do the job.