.45 Fast Twist Barrel Length

[Good Cheer]

Who has experience with nominally .45-.46 caliber barrels, of how various barrel lengths effect accuracy with distance?
I'm about to have another New Englander reworked. This time .455 bore diameter (still working out the groove depth) x 20" twist. New Englander's have about 27" of barrel. And what I'm trying to decide on is how long to make that .455 bore barrel. I can look back in history at Volunteer's and Whitworth's and such to see the barrel lengths they used but that actually doesn't help answer the question of how much barrel I'd need seeing as the piece is going to be scoped. In other words my accuracy is not going to be effected by the sight radius.

If one looks at the 45-70 trapdoor carbine, did that 26" barrel result in reduced potential accuracy except for the reduced sight radius? Was the reduction in muzzle velocity enough to significantly effect longer range accuracy?

If anyone cares to join in all thoughts are welcome.

[Nobade]

I don't think barrel length is going to affect accuracy since you're going to scope it, other than lighter will be harder to hold. Velocity will be lower with a shorter barrel but that won't change accuracy.

[Castaway]

Your accuracy won’t be diminished as stated, and like has been said, your velocity will. The reason the old rifles had such long barrels was to get the most from black powder as a propellant. You’ve not mentioned the expected velocity you intend to achieve, nor have you said what distance you’re talking about.

[country gent]

The shorter barrel will change some things.
1) velocity will be slightly lower
2) sight radius will be shorter if using Iron sights, a scope it dosnt matter
3) balance point of rifle will change some
4) rifle will be lighter and hence recoil will be heavier

As far as inherent accuracy goes I dont think youll loose any accuracy and may gain some as follow tru with the shorter barrel wont be as critical ( less barrel time to control).

[Woodnbow]

I have .45 and .40 caliber barrels on the New Englander and High Plains Sporter stocks so 24 and 26” barrels. I use only Swiss 2 and 3f powder and am getting very good useful velocity from bullets up to 405 grains. The 26” .40 really likes Swiss 1.5f but I’m shooting 400 grain paper patched bullets from it. Accuracy is superb.

[Good Cheer]

I have .45 and .40 caliber barrels on the New Englander and High Plains Sporter stocks so 24 and 26” barrels. I use only Swiss 2 and 3f powder and am getting very good useful velocity from bullets up to 405 grains. The 26” .40 really likes Swiss 1.5f but I’m shooting 400 grain paper patched bullets from it. Accuracy is superb.

With those barrel lengths are the boolits slowing through transonic somewhere downrange?

[greyhawk]

I don't think barrel length is going to affect accuracy since you're going to scope it, other than lighter will be harder to hold. Velocity will be lower with a shorter barrel but that won't change accuracy.

In that 26"-28" range of barrel length I dont think velocity will be affected as much as we imagine compared to the older target rifles (check out the Swiss calculator) --can always move to FFFg powder as a counter.

1)Those old guys wanted the extra sight radius (you dont need with a scope)
2)The military fashion of the day was longer barrels - largely influenced by use of bayonets - the other guy had his sticker four feet ahead of him, we had to do that too or else get stuck before we could stick him - sounds kinda foolish now but with an empty barrel and that sharp blade comin at you ---10 inches extra reach mattered a lot....

[Woodnbow]

They do but they really are sub 500 yard rifles. In .45 if you want to shoot long range you need heavy bullets and powder charges. 520 grains over 110 grains 2f Swiss is an excellent recipe. The 24” High Plains gives up less than eighty fps compared with the same load in my 32” Gibbs. But recoil is severe in the carbine so I typically load with a 400 grain bullet over 80 grains of black.

[Good Cheer]

Passing through the trans sonic range would definitely effect accuracy and available velocity of course being effected by barrel length, hence post #1.
I need to do some more tests with long boolits in .458 bore before ordering this .455.

[HWooldridge]

Who has experience with nominally .45-.46 caliber barrels, of how various barrel lengths effect accuracy with distance?
I'm about to have another New Englander reworked. This time .455 bore diameter (still working out the groove depth) x 20" twist. New Englander's have about 27" of barrel. And what I'm trying to decide on is how long to make that .455 bore barrel. I can look back in history at Volunteer's and Whitworth's and such to see the barrel lengths they used but that actually doesn't help answer the question of how much barrel I'd need seeing as the piece is going to be scoped. In other words my accuracy is not going to be effected by the sight radius.

If one looks at the 45-70 trapdoor carbine, did that 26" barrel result in reduced potential accuracy except for the reduced sight radius? Was the reduction in muzzle velocity enough to significantly effect longer range accuracy?

If anyone cares to join in all thoughts are welcome.

You didn’t mention expected bullet weight - that will make a difference.

I once had a Mowrey .45 ML with a 28” barrel and 1-24” twist. Wouldn’t shoot patched ball worth a flip but was quite accurate with Maxi Balls. It was a light rifle and hurt my shoulder with 70 grs of 3F but killed deer like nobody’s business…

[Good Cheer]

There's a range of weights suitable to 20" twist, obviously hedging up on the heavy side for .45 rifles. I'm thinking 550 grains is the heaviest in hand but a long NEI spire point boat tail* is a gotta try it as well! And to state the obvious, whatever the piece preferred would dictate what shot best. Boolit designs for black powder at long range are well known due to the huge amount of personal experience gained by shooters in black powder cartridge shoots. That knowledge base is totally applicable to muzzleloading.
The reason for asking the original question is thinking that I'd have a supersonic muzzle velocity and then with distance slowing into the transition range and then subsonic. And, that barrel length would play into muzzle velocity and thence how far downrange the transition would be happening. From the responses above I'm led the believe that my expectations of supersonic muzzle velocities may be way off base. So far what I've worked with is as 24" twist .458 bore (.470 groove) with 27" barrel length. I need to chronograph some more heavy boolits in that 27" barrel to gain data.

*It's lighter though longer.

[Good Cheer]

By the way, with Lyman's #457124 in the 27" barrel 90 grains of Goex FFg gave 1285FPS.
That was the heaviest charge I bothered putting over the chronograph then (March of 2013) because 80 grains cut one hole at 50 yards but 90 opened up the groups. That was shooting lubed lead, 420 grains of straight soft lead sized .457" over punched cardboard wads.

[Sandro_ventania]

If the initial velocity will be subsonic, the pipe length won't make a difference; choose the most balanced length. If you're going to start at supersonic speed, then the longest possible length is desirable, because the less time it spends after the transonic transition, the better.