i thought pellets and bullets rose from the from the muzzle to an apex and then began to drop, making the trajectory an arc and giving 2 poa/poi.
yup...we all tend to droop over time. Compensation is the key.
Why would several excellent companies, making quality spring piston rifles all have "problems" with barrel droop. If you can make a rifle capable of one hole groups out to 25 yards or so, why would barrel droop be a problem?I've been thinking about this for years and I think I have an answer. A well made rifle puts the centerline of the rifle bore and the centerline of the scope( when the scope is adjusted at the center of it's range) pretty much parralel. If that's true, the rifle would NEVER shoot to point of aim. The bullet starts dropping from it's centerline as soon as it leaves the muzzle. With an airgun, that drop amounts to several inches at , say 50 yards. Well, the pellet starts out about 1 1/2" below the centerline of the scope and at 50 yards could be maybe 6" low. That's a LOT for a scope adjustment to make up. Back when iron sights were more popular, they could be built to copensate for that easier because they were closer to the centerline of the bore. Building a rear sight a bit higher and with more adjustment is a piece of cake for a good gun maker. A fast, centerfire rifle bullet drops WAY less than a pellet, and is normally sighted in at much longer distances. This next bit is all nominal for explanation purposes. A 1 degree adjustment in the scope elevation would put the POA and POI at the same point because of the flatter trajectory of the faster rifle. Comparitively, a pellet has a rainbow trajectory that needs a LOT of adjustment to tilt the ever-falling pellet up to get to the POA. A pretty, computer designed picture here would certainly help me explain my concept. Not in my skill set.
Here is what I believeAirgun barrels are not hardened steel like PB barrels. Continued "smacking" down on a hollow tube that is 2 feet long (give or take) has to eventually lead to bending it slightly. "droop"
Quote from: wolverine on September 19, 2020, 02:04:07 PMi thought pellets and bullets rose from the from the muzzle to an apex and then began to drop, making the trajectory an arc and giving 2 poa/poi.Another pic on pellet trajectory.
Quote from: Joey on September 19, 2020, 10:26:52 AMWhy would several excellent companies, making quality spring piston rifles all have "problems" with barrel droop. If you can make a rifle capable of one hole groups out to 25 yards or so, why would barrel droop be a problem?I've been thinking about this for years and I think I have an answer. A well made rifle puts the centerline of the rifle bore and the centerline of the scope( when the scope is adjusted at the center of it's range) pretty much parralel. If that's true, the rifle would NEVER shoot to point of aim. The bullet starts dropping from it's centerline as soon as it leaves the muzzle. With an airgun, that drop amounts to several inches at , say 50 yards. Well, the pellet starts out about 1 1/2" below the centerline of the scope and at 50 yards could be maybe 6" low. That's a LOT for a scope adjustment to make up. Back when iron sights were more popular, they could be built to copensate for that easier because they were closer to the centerline of the bore. Building a rear sight a bit higher and with more adjustment is a piece of cake for a good gun maker. A fast, centerfire rifle bullet drops WAY less than a pellet, and is normally sighted in at much longer distances. This next bit is all nominal for explanation purposes. A 1 degree adjustment in the scope elevation would put the POA and POI at the same point because of the flatter trajectory of the faster rifle. Comparitively, a pellet has a rainbow trajectory that needs a LOT of adjustment to tilt the ever-falling pellet up to get to the POA. A pretty, computer designed picture here would certainly help me explain my concept. Not in my skill set.Perhaps "barrel droop" isn't an issue for the majority of airgunners outside the USA that use "iron sights". I've read that some makers (such as Diana) "design in" droop to accommodate the tall front sights with the interchangeable inserts (however I don't know if I completely believe this story). If the droop issue was only related to "manufacturing tolerances" then there would be Dianas with both "snoop and droop". Since droop is the "common issue" I do tend to believe that droop is "designed in" for whatever reason..........I've never handles a Diana "fixed barrel" but I just finished looking a a lot of RWS54 pics and it certainly seems that the barrels are "drooping" relative to the receiver.Anywhoo....I do know that "droop" is a reality for guns such as the RWS34 that I looked at decades ago at an airgun show. The droop with the brand new RWS34 was so pronounced that it was easily seen by eye without the need for a straight edge as a reference. Rather than "fix a droop issue" RWS offers the "Lock Down mount" with .025" elevation compensates for barrel droop...........https://www.pyramydair.com/product/rws-lock-down-1-pc-mount-w-1-rings-11mm-dovetail-barrel-droop?a=2406LOL......I bought one of these mounts and used it on my HW95 resulting a poi 4" above the poa at only 18 yards!