I have a Weihrauch HW80 in .25 cal with a 30 cm barrel length, and with standard spring I get 150 mps with the 25 cal JSB Excact pellets,. With a tuning kit I was able to achieve 167 mps. But I am not satisfied, and wonders if the 40 cm or the 50 cm barrel will give the highest velocity?
HW/Weihrauch What barrel length will give highest velocity for the Weihrauch HW80 in .25 cal?
- Thread starter Norseman
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I doubt increasing the length will increase velocity. Springers only have so much swept volume to work with. They exhaust the pressure differential pretty quickly. The HW80 has a relatively short stroke so it doesn't have a lot of swept volume when compared to other magnum springers. Bigger magnums may benefit from longer barrels but I think you'll find shear size of a 25 cal bore exhausts all the usable air pressure from your 80s tube in that first 300mm. Any additional length would probably just add drag and hold sensitivity.
I could be wrong but I seem to recall people losing energy going from 22 to 25 on HW80/R1s. Typically those guns pick up power going up in caliber. Reportedly they lose power going to 25 which would make me think the gun doesn't have enough swept volume to be efficient in 25 in the first place.
This is all theoretical based on general principles and second hand reports. Hopefully someone will respond that has done what you're contemplating.
Good luck
I could be wrong but I seem to recall people losing energy going from 22 to 25 on HW80/R1s. Typically those guns pick up power going up in caliber. Reportedly they lose power going to 25 which would make me think the gun doesn't have enough swept volume to be efficient in 25 in the first place.
This is all theoretical based on general principles and second hand reports. Hopefully someone will respond that has done what you're contemplating.
Good luck
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The quick and easy solution is just to switch to the lighter 20gr FTTs over the (I assume) 26gr JSBs
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Hmmm...
Id figure being a air gun you just get a pop of air not expanding gas like a pb , so nothing much on long or short but stability .... maybe? Then maybe with that longer = more friction or drag on the pellet / maybe slower leaving the muzzle?
Now in a 80 hw lists the long and carbine specs so look see what one gains or loss . Bit its not going to be a oh my gosh wether in the +/- ( like 3fps. )
www.weihrauch-sport.de
Id figure being a air gun you just get a pop of air not expanding gas like a pb , so nothing much on long or short but stability .... maybe? Then maybe with that longer = more friction or drag on the pellet / maybe slower leaving the muzzle?
Now in a 80 hw lists the long and carbine specs so look see what one gains or loss . Bit its not going to be a oh my gosh wether in the +/- ( like 3fps. )
HW 80 SL - Weihrauch Sport
Probably the best break-barrel air rifle available, often classified as "the work-horse". The robust construction, the excellent accuracy and the powerful mainspring guarantee an extraordinary efficiency and penetration power especially at longer distances. Sporting hardwood stock, cheekpiece on...
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A good write up on the topic here:
“. . . discovered that the optimum barrel length for a spring-piston airgun was around 6 inches. . . . once the pellet accelerates to maximum velocity inside the barrel it COASTS the rest of the way!
How barrel length affects airgun performance | Blog | Pyramyd AIR
It's time to examine the effects of barrel length on airgun performance.
www.pyramydair.com
“. . . discovered that the optimum barrel length for a spring-piston airgun was around 6 inches. . . . once the pellet accelerates to maximum velocity inside the barrel it COASTS the rest of the way!
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This may help somewhat.
Pellet Rifle Swept Volume formula:
Rifle bore radius squared x Pi (3.14159) x piston stroke = cubed mm. Convert to cubed centimeter by moving decimal point 3 positions left.
Example:
HW95L .22 caliber 26 mm Bore radius = 13 squared (1/2 diameter) = 169 mm x Pi (3.14159) = 530.929 x HW95L Stroke 85 = 45,128.9 mm cubed. Convert to CC (cubic centimeter) = 45.128 or 45.13 CC for Swept Volume.
Pellet Rifle Swept Volume formula:
Rifle bore radius squared x Pi (3.14159) x piston stroke = cubed mm. Convert to cubed centimeter by moving decimal point 3 positions left.
Example:
HW95L .22 caliber 26 mm Bore radius = 13 squared (1/2 diameter) = 169 mm x Pi (3.14159) = 530.929 x HW95L Stroke 85 = 45,128.9 mm cubed. Convert to CC (cubic centimeter) = 45.128 or 45.13 CC for Swept Volume.
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There was a book that came out in the late 80s early 90s I think. The author experimented with barrel length and if my sometimers brain is correct he found 9 inches to be optimal.A good write up on the topic here:
How barrel length affects airgun performance | Blog | Pyramyd AIR
It's time to examine the effects of barrel length on airgun performance.www.pyramydair.com
“. . . discovered that the optimum barrel length for a spring-piston airgun was around 6 inches. . . . once the pellet accelerates to maximum velocity inside the barrel it COASTS the rest of the way!
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I have never heard of a R1/HW 80 with a 11.8" bbl? How big are your arms? Cuz they are gonna have to be pretty big to cock that thing?
My R1 has the 500MM barrel 19.685" and I have to cock it with my Right Arm because my Left Arm that I normally use, isn't strong enough to do it more than once or twice.
My 2 HW 35's E and EB have 19" bbl and 16" bbl and the 16" EB bbl. is noticeably harder to cock than 19" E bbl.
All that said, the shorter barrel will produce Higher Velocity for the reasons stated above, and there is also less friction/drag on the pellet with the shorter barrel.
Pics of the gun please? Never seen a SBR Pellet gun?
Randy
My R1 has the 500MM barrel 19.685" and I have to cock it with my Right Arm because my Left Arm that I normally use, isn't strong enough to do it more than once or twice.
My 2 HW 35's E and EB have 19" bbl and 16" bbl and the 16" EB bbl. is noticeably harder to cock than 19" E bbl.
All that said, the shorter barrel will produce Higher Velocity for the reasons stated above, and there is also less friction/drag on the pellet with the shorter barrel.
Pics of the gun please? Never seen a SBR Pellet gun?
Randy
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Increasing barrel length on a springer does not increase velocity in the same manner as it does in a PCP.
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Best I could ever get out of my 25 R1 was with the old venom tune kit that came with an upgraded piston and a VERY long spring with steel guide, pushed Baracudas 550fps and Crow Magnums at 602fps. Not the smoothest shot cycle but sure did smack!
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As stated above, any barrel on a springer much over 9-11 inches depending on caliber/power will start having a decrease in velocity due to drag/friction on the pellet. I am assuming your short barrel has a sleeve extension for a cocking aid. My Hatsan 135 .25 caliber has a 11 inch barrel. Shoots at “approximately” 30 fpe. 800 fps. It has a sleeve for a cocking aid and is still a beast cock. And a blast to shoot.
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Yes, the whole reason for the 16" bbls on the HW35 EB (Export Beeman) was to increase velocity. And Beeman himself requested it. I never realized that mine had a shorter barrel until I got my HW35E about 10 years ago. I didn't even notice it then until the two guns were sat side by side. I did notice that it was easier to cock.
Randy
Randy
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Low- and medium power springers don't need much any barrel length to get to places, but magnum springers are different. Hector Medina has stated around 15" is a limit with these where going under starts to lose velocity and KE. For this reason, I would not consider the 310mm "ultra-K" Weihrauch barrel for a full power HW80 - it would work fine in a 12 fpe, or 10J or 7.5J gun, though.
My H135 .25 cal with a full-length barrel gets up to 900 fps at the muzzle.
My H135 .25 cal with a full-length barrel gets up to 900 fps at the muzzle.
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The 80 is barely a "Magnum" springer it's got 30mm piston and only 80mm stroke. Most magnums have well over 100mm of stroke. There's really not a lot of swept volume in the 80. And it's not pushed for very long. The large 25 caliber bore will consume that volume very quickly. There's no need to worry about losing velocity from any barrel length.
There's been a few people that have found their R1s and 80s less efficient in 25 than the same gun was in 22. I believe it's because the caliber exceeds the volumetric efficency.
There's been a few people that have found their R1s and 80s less efficient in 25 than the same gun was in 22. I believe it's because the caliber exceeds the volumetric efficency.
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You may be thinking of Cardew's The Airgun from Trigger to Target. If my creaky old memory can be trusted...they rigged up a .177 BSA Mercury barrel-cocker with extensive testing sensors and did some precise measuring. They concluded that the max-velocity barrel length for this gun (which I assume was under 12 FPE in accordance with UK regs) was 9 to 11 inches.
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Years back, I built four custom tuned R1 in .22 cal. I had experimented with calibers to find which was most effiecent. The .22 cal was by far. I called them lightning models, avg 835 fps with CP 14.3 gn pellets. By cutting the barel down 3.5 inches and cutting off the choke we gained 30 plus fps and also increased accuracy on all four rifles. The other calibers lost velocity and accuracy when we shortened/ removed the choke. Use this info however you want....
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Airshot, did you shorten a full-length HW80 barrel? The 3.5 inches would make it really close to the basic K barrel, which is 410mm (16.1") in length. The K barrel tapped for a moderator is a whopping 100mm shorter than that, or just a hair over a foot in length.
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Ron, I hear you on the .25 cal, but do you think the smaller calibers wouldn't suffer any velocity / KE loss from having just 12" of barrel? As I said, that is demonstrably enough for smaller springers, but the HW80 sits at the border, like you said. Many people have opined .177 cals need longer barrels to reach their potential, and that should be so, to a lesser extent, with the .20 and .22 cals, too, relative to the quarterbore.
When Hector opined about the 15" lower limit, he wasn't talking about the biggest springers around. Magnum Dianas, producing around 30J / 22 fpe at the muzzle were in this category. The HW80 isn't too far back from those, and power-tuned specimens, like Airshot's, are just as powerful.
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I'm going to use the Cometa USC for reference here. It has a ~9" barrel and I'm getting 16fpe in .177, 17fpe in .22, and 17fpe in .25 cal all with standard weight lead pellets (20gr FTTs in the .25)
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