That is an extreme build, and I do enjoy reading your build threads, you push into boundaries very few have ventured, off the beaten path.
-Matt
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Barrel Length, the seldomly understood calculus
- Thread starter Stubbers
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That is an extreme build, and I do enjoy reading your build threads, you push into boundaries very few have ventured, off the beaten path.
-Matt
What I’ve always wondered about is the barrel length on springers. Everything I’ve read and my own personal experience is that springers tend to develop nearly 100% of their velocity in the first 9” or so. I cut a couple Chinese guns down into carbines back in the day and noticed little loss in velocity from it.
I suspect that the barrel length on most springers today has more to do with cocking leverage than power or efficiency, especially when the barrel length remains the same from .177 to .25.
I suspect that the barrel length on most springers today has more to do with cocking leverage than power or efficiency, especially when the barrel length remains the same from .177 to .25.
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Not just cocking leverage, but reduced muzzle report and muzzle flip, taming the shot cycle as the pellet coasts.
This applies to most airguns, however springer internal ballistics are a bit different.
Enjoy the read if you partake...From the same guy as the pcp internal ballistic article, Domingo Tavella...brilliant guy.
-Matt
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Earlier in this thread it was requested to have to different barrel lengths tested, with the exact same rifle. So in the name of science, etc...
The rifle is an American Air Arms, Evol Magnon 30 caliber, with a 1900 psi regulator setting, 83 cc's of plenum space, stock-ish 30 caliber porting, and moderate hammer spring tension because of the short barrel and waisting air/accuracy. The barrel's are nearly identical in form and bore conditioning/treatment. The barrel's used on the Magnon receiver were 15" and 18" respectively. (381mm 457mm for you metric folks). They screw onto the receiver to meet the transfer port, so there is no disruption of any kind to the gun other than the barrel swap. The chronograph sat at 10 yards.
The 15" barrel
JSB Heavy 50.15 grain pellets 810 fps
JSB Hades 44.75 grain pellets 827 fps.
The 18" barrel
JSB Hades 44.75 grain pellets 846 fps
JSB Hades 44.75 grain pellets. 867 fps.
The rifle is an American Air Arms, Evol Magnon 30 caliber, with a 1900 psi regulator setting, 83 cc's of plenum space, stock-ish 30 caliber porting, and moderate hammer spring tension because of the short barrel and waisting air/accuracy. The barrel's are nearly identical in form and bore conditioning/treatment. The barrel's used on the Magnon receiver were 15" and 18" respectively. (381mm 457mm for you metric folks). They screw onto the receiver to meet the transfer port, so there is no disruption of any kind to the gun other than the barrel swap. The chronograph sat at 10 yards.
The 15" barrel
JSB Heavy 50.15 grain pellets 810 fps
JSB Hades 44.75 grain pellets 827 fps.
The 18" barrel
JSB Hades 44.75 grain pellets 846 fps
JSB Hades 44.75 grain pellets. 867 fps.
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Port diameter makes a huge difference, as it greatly impacts the 'mass flow rate' feeding the barrel and the potential shift when changing barrel length. Likewise so does plenum volume. Any chance you know what the stock port diameter is for this gun, or plenum volume? Was the 810/827 fps with 15" at its plateau or de-tuned away from peak? Assuming you didn't change any hammer settings, only the barrels here?
Thanks for the data!
-Matt
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I couldn't even guess at those numbers, but I'll work on getting the answers for more reliable data. The gun is de-tuned slightly, with less pressure, but has a large 46cc plenum extension installed for volume.
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So 37cc + 46cc with his extension for 83ccs? Unless its a 37cc with 6 cc extension making for 46cc which makes less sense haha. That information helps, having one piece of the data helps extrapolate the other.
I did some tinkering just now on my spread sheet, woke up at 4:30am and a light bulb clicked to help me refine the only number I have to fudge with on my spread sheet, which is barrel volume / distance that is considered 'effective' or rather the distance at which the pellet would be in the barrel during valve closure, and adding more air contributes no meaningful energy. Prior to this I used an inferior method that required some guess work on my end, well, no more...
15" barrel with 50.1 gr
18" barrel with 50.1 gr (1 fps off
I blame friction! Lol)Cool beans! Thanks for the data @Airgun-hobbyist ...now my spreadsheet estimates barrel length changes far more accurately with my update! Teamwork makes the dreamwork!
-Matt
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