Barrel Length confusion

[snakebite4767]

I've been considering barrel length on these Air Rifles. I took a look at some of the older post, but really didn't find much definitive information.
I understand that with a Barrel Break springers that the longer barrel gives more leverage to cock the gun.  And after having that Magnum Hatsan, I can certainly appreciate that. But.. other than providing a better fulcrum, what else does it do? I've seen them from under 10" to almost 20", and on guns that appeared to be relatively the same,and were rated at virtually the same FPS, so it leaves me confused.

I understand barrel length, twist, and powder burn rate pretty well in Powder Burner type guns. Fast powder would normally not be used in a long barrel because the bullet would have to travel further down the barrel after the Powder Burn was complete.... thus, slowing it down. Like wise with a slow powder... it would still be burning when it runs out of barrel...
It seems like the same would apply to a Air Rifle. I can see that on a PCP gun, where I assume the Pulse width can be adjusted (Fast powder, Slow powder type effect)  barrel length could be variable and length adjusted for the best all around performance.  However, it seems that most of the spring guns would have a pulse width that was pretty much the same... which would tend to make me expect to see the barrel lengths the same. I understand  that the Magnum guns have more spring, which would make the Pulse width longer, thus getting some benefit from a longer barrel.

One other question... why are some of the barrels Choked? I would think that when the soft lead pellet obturates  and fills the barrel, it would be counter- productive to  "Choke" it back down at the point it exits the barrel.

Hummmm?

Snakebite

[David.Soliman]

There are two factors that come into play here, first as the length of the barrel increases the acceleration of the pellet increases thus a longer barrel the faster the pellet (and that is the general rule for most PCPs), but also when the length of the barrel increases the friction between the pellet and the barrel itself increases. So it is important to find a balance between the two, the friction forces trying to stop the pellet and the pressure of the air pushing the pellet forward.

To my knowledge it is mostly guess work and trial and error when it comes to springers, the choke would also greatly affect the pellet speed, a shorter barrel will benefit more from a tight choke.

Folks have seen different results after shortening their barrels, on some rifles the speed increases on others it's the opposite. And I recall seeing a spreadsheet (can't remember where) showing speed vs. barrel length, too long barrel gives low speeds, too short also gives low speeds.

[JimL911]

PCP's/CO2's can benefit from a longer barrel as the expanding air has more time to get the pellet up to speed. With springers the pulse of air is so short a pellet achieves max velocity in a much shorter distance. I believe 10" is the shortest you want to go to max speed and accuracy. This is fine for low powered guns or an underlever like the TX HC, but for normal powered break barrels you need that extra leverage for ease of cocking. The differing barrel lengths are for easier cocking(longer), ease of handling(shorter), aesthetics and balance.
Chokes help to make a barrel less pellet fussy getting the head and skirt closer to the same size.

[Flatcar1]

Another thing to consider on a springer, the shorter the barrel the less time the pellet spends in the barrel, called lag time. Usually the less lag time, the more accurate the rifle, because of less recoil affect before the pellet exits. If you are using open sights the longer the barrel the longer the sight radius. If you are using a scope on a springer anything past 12" doesnt make much impact. Also choking is realy not important if you find a pellet that is accurate in your gun. Choking helps to make a wider selection of pellets shoot better in your specific gun because of variations in size. Some pellets are very loose and some fit snug. Choking helps the loose fitting ones be more accurate. I hope I havent confused the issue, just my 2 cents FWIW

[snakebite4767]

Hey guys... thanks for the input. Both the comments about Choking make sense to me. I can, however, see that finding the right pellet would be the best answer for a given gun. It appears that it might be best to use a short barrel with a long Muzzle Brake, so as to provide leverage for cocking. I'm enjoying learning about Air Guns. Thanks again.

Snakebite

[Kailua]

I think the barrels flexes more as the barrel gets longer in spring airguns.  Not really noticeable if the flex is consistent POI should remain consistent.  JMO