velocity loss -v- barrel length

[bigted]

setting and allowing my mind to wonder the other day I pondered an oft asked question...what does barrel length have to do with velocity?

in smokeless powder you lose a fair amount of go with the shorter barrels so for grins I decided to look in my Lyman bp book for the difference in velocity versus barrel length.

shocked I found that the difference between a 24 inch barrel shooting a Lyman shocker of 420 grains versus a 32 inch barrel with the same boolit and charge of ...[arbitrarily]...80 grains GOEX 2f powder. the difference is around 100 FPS... 50 cal. looking at the 22 inch barrel in the same category I find that the loss is just about the same...not much more.

comparing the 54 cal I found just about the same thing.

so my question is thusly...what is the advantage of a 34 to 36 inch barrel in BPCR rifles instead of the shorter ... more compact barrel length of say 24 or 26 inch? I do know that the longer sight radius gives a more accurate and repeatable sight picture but as for ballistics...what is the advantage?

there has to be a length of barrel that is optimum for all area's of concern but is this measurement the 30 plus length that we always see on these rifles? there has to be a point of diminished returns and I guess that is what im looking for here.

take for example my22 inch barreled Ruger #1 in 45-70... I shot it the other day with 70 grains GOEX cartridge pushing a 405 grain accurate arms boolit with a 1/8th cookie and im saying that it spits that boolit rite down the lane. I would not feel under gunned shooting a moose with that combo so hence the question on barrel length versus power and ballistics.

just an exercise in mind m@$!&%#@(!0n... thankyou for the opportunity to resurrect this subject for some thoughts.

[Matt85]

my opinion: with modern BP, barrel length doesn't make a huge difference in velocity. as you suspected barrel length has more to do with sight picture with modern guns which is why I prefer longer barrels. ive heard using poor quality BP that doesn't burn as well a longer barrel might assist in burn time but ive never seen any proof of this. when it comes to barrel length I can shoot a better group with my 50 cal long rifle with a 42" barrel then I can with my 58 cal Jaeger with a 32" barrel. the extra 10" of barrel makes for a outstanding sight picture and yields better accuracy. as a final note this also depends on your sights. ive found that peep sights aren't as dependent on barrel length as standard irons.

-matt

[NickSS]

It's mostly accuracy of a longer sight picture but also sight settings when you change ranges. Most tang sights give finer adjustments with longer barrels than with shorter. This helps when you are zeroing in a rifle at a relatively small target at 500 meters. Also the longer barrels add weight and when you are shooting 50 or more rounds in a day weight of the rifle counts towards shooter comfort. I have a 50-70 C sharps 74 carbine with a 26 inch barrel. It is a dandy for hunting but I tried it at silhouettes one time and got so punished by the recoil that I started flinching and missing as a result and that rifle is about 9 pounds.

[TheCounty]

Concerning maximum velocity alone, the rule of thumb if my memory serves right is 36" to 39" for BP and about 28" for smokeless. Of course caliber, BP type, etc can all varry these slightly. Not sure if true but have read that additional barrel length may actually may lower muzzle velocity due to bullet drag due to friction. My memory is not perfect, but I believe this info is covered in an old Gun Digest, American Rifleman or such...too big of a pile to go searching. Not sure for BP, but for reloading smokeless the loss in fps from a 24" barrel down to a 18" barrel is roughly 50 fps per inch. Big variations are likely due to powder speed, case design, twist etc, etc, ...but for discussions at the bar over a whiskey they suffice and seem to pan out.
Cheers
TheCounty

[Texantothecore]

IIRC, 28" is optimal for smokeless.

The length of the black powder barrel may have to do more with the amount of powder used and it's grain. 3 Fg may be a shorter barrel than 2 Fg, for instance. For MLs a longer barrel may be the ticket.

[Char-Gar]

I know very little about black powder, but what little I do know leads me to believe that long barrels just give added sight radius and weight stability to help the front sight stay steady. The progressive burning nature of black is almost nil.

Smokless powder continues to burn down the barrel and after it stops the velocity increase drops off to a point and then the extra friction with the long barrel begins to slow the bullet down. When the velocity benefits of the longer barrel rolls snake eyes, depends on caliber, bullet weight, barrel length and type of powder.

The real downside to short barreled lighter black powder rifles in added recoil. That is why the US Govt. had a rife load (70 grains of BP over a 500 grain bullet) and a carbine load of 55 grains of BP over a 405 grain bullet. The rifle load was safe enough in the carbine, but the extra recoil was more than the smaller and lighter Cavalryman could handle. They had maximum weight requirements to "Jine the Cavalry", with 140 being the max for trooper and 160 for officers. Big men need not apply!

[Gunlaker]

My 34" barreled Shiloh is a little quicker than my 30" barreled C. Sharps in .45-70 when loaded with the same powder charge. Not a by a lot, but maybe 20fps or so IIRC.

Chris.

[bigted]

cool...as I suspected...the shorter barrels are best for hunting and brush bucking. the longer are best for long stretch's of shots to keep the beating down and to aid in sighting.

I have a 45-120 that is fun but the 30 inch heavy on the sharps frame is way too heavy to pack un the brush so I was contemplating getting it shortened for the hunting it should be doing or maybe just send it back to Shiloh for a rebarrel to 44-77 maybe.

also I have a 40-70 BN barrel that is 26 inch's long. im bettin that this would be wonderful on a #1 setup Ruger....with a unertl 6 or 8 x scope mounted....sounds like a neat setup to me .

[Jeff Houck]

cool...as I suspected...the shorter barrels are best for hunting and brush bucking. the longer are best for long stretch's of shots to keep the beating down and to aid in sighting.

I have a 45-120 that is fun but the 30 inch heavy on the sharps frame is way too heavy to pack un the brush so I was contemplating getting it shortened for the hunting it should be doing or maybe just send it back to Shiloh for a rebarrel to 44-77 maybe.

also I have a 40-70 BN barrel that is 26 inch's long. im bettin that this would be wonderful on a #1 setup Ruger....with a unertl 6 or 8 x scope mounted....sounds like a neat setup to me .

The primary reason for the very long rifles for the infantry was because a great deal of the fighting was hand to hand combat. For the infantry soldier that meant bayonets mounted on the end of their rifle. The longer the rifle the better. Can you imagine facing an enemy with a bayoneted rifle that's two feet shorter than you opponents? Not a real positive moral booster. The longer sight radius was an added benefit. Velocity increase was only on the order of 5ish fps per inch for the longer barrels.

Jeff Houck