GTA
All Springer/NP/PCP Air Gun Discussion General => Air Gun Gate => Topic started by: DWSmith on July 05, 2015, 06:28:18 PM
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Do lever type rifles suffer from barrel droop?
I can understand why a breakbarrel would succumb to it except maybe the LGV. Is shimming the scope the best way to correct the ailment?
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Any gun can suffer from barrel droop, in that the barrel and optics might not line up, correctly.
I believe it has been shown to be a myth that repeatedly cocking a break-barrel actually physically bends the barrel. I think it's more commonly accepted that the lockup of the gun can cause the barrel to point down, slightly. But in either case, an underlever or sidecocker would not be susceptible to either of these issues.
IMO, this kind of barrel droop is best to be fixed at the joint. Perhaps the lockup/jam needs to be strengthened, and/or the breech seal might be too thick?
If there's nothing wrong with the joint, the rail, the mount, or the optics, and there's still a significant disparity in bore to axis alignment, I often choose to bend the barrel. The barrel is mild steel and is easily bent as needed. Even pb rifle barrels can be bent quite easily.
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In my experience they all have it....... Tweaking the barrel and or shimming is best in MHO.
Example: The worst one I have come across is my 48= 17" low at 20 yards...major droop. Some of it was attributed too the factory barrel sleeve. But even without the sleeve it still had a fair amount of droop...==== Tweaked the barrel almost to a perfect zero , then turned the clickers a hair to fine tune. Love the 48 . One of my favorite shooters..
(http://i1193.photobucket.com/albums/aa347/NPetey/48/IMG_0635_zpsa92321a3.jpg) (http://s1193.photobucket.com/user/NPetey/media/48/IMG_0635_zpsa92321a3.jpg.html)
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My experience is very limited. 1 underlever an XS46. I have no problem with barrel droop.
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Another reason "droop" is common in air rifles is because of the low velocity and BC of diabolo pellets. If shooting at longer ranges, it is common to run out of adjustment. You can buy +20MOA rings/mounts for your scope. Long distance pb shooters use them, too.
But my pet theory on why even underlevers can suffer droop is due to the recoil. The backwards recoil should technically be a little more than the forwards. But because you are holding the gun in your hands and against your shoulder, the net effect is a bit of forward movement of the gun. The forward recoil moves the barrel forward and down before the pellet leaves the barrel. So a springer barrel that is perfectly straight has built-in droop. Vs a pb, that will have a little built-in rise.
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Another reason "droop" is common in air rifles is because of the low velocity and BC of diabolo pellets. If shooting at longer ranges, it is common to run out of adjustment. You can buy +20MOA rings/mounts for your scope. Long distance pb shooters use them, too.
But my pet theory on why even underlevers can suffer droop is due to the recoil. The backwards recoil should technically be a little more than the forwards. But because you are holding the gun in your hands and against your shoulder, the net effect is a bit of forward movement of the gun. The forward recoil moves the barrel forward and down before the pellet leaves the barrel. So a springer barrel that is perfectly straight has built-in droop. Vs a pb, that will have a little built-in rise.
Interesting theory.....
????????????????????????? Running out of adjustment??????????????= Please!
There is no reason to run out of adjustment...None........... If people would learn to setup a scope properly , Scope mfg's wouldn't have to put up with all the returns and bad press.....and you wouldn't hear " I ran out of adjustment" ....... People do your homework and the whole experience will be much more rewarding for all parties--------
Hatsan Chop! ........... I know this one.........
https://youtu.be/OlMJfX_V6Ic
Happy Shootin !
Petey
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Seems to me… AGs shoot just fine with the iron sights they were designed with at distances they designed for. When mounted with a scope whose line-of-sight is two inches higher than the bore, I would expect a POI somewhere around two inches low, all things being perfect. Certain individual AGs will shoot a bit higher or lower due to an accumulation of manufacturing tolerances, but IMO there is no such thing as (inherent) barrel drop.
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My Diana 54 sure had a lot of "droop". Solved completely by a droop compensating mount. I don't know why, just the way it is. I can't say if one style lever is more prone to it. But if you have enough droop, just buy the mount, I think it was around 20 bucks or so at optics planet, UTG if I remember correctly.
Dan
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Since you are asking I suspect you are worried about it. My most accurate spring rifle has a ton of droop. I find it has zero effect on accuracy. I either shim the back ring or use a drop compensated/adjustable mount. It's really no big deal. It's a one time set up and you never think about it again. Pick the rifle you like and deal with it as needed when you mount the scope and move on.
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Hatsan Chop! ........... I know this one.........
https://youtu.be/OlMJfX_V6Ic
Happy Shootin !
Petey
Nailed it right on the head!
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When mounted with a scope whose line-of-sight is two inches higher than the bore, I would expect a POI somewhere around two inches low, all things being perfect. Certain individual AGs will shoot a bit higher or lower due to an accumulation of manufacturing tolerances, but IMO there is no such thing as (inherent) barrel drop.
That doesn't cover issues that some guys run into, such as 17" low at 20 yards. Even accounting for gravity, you would have at most 4" disparity to cover.
I realize there's a disparity between bore and sight axis. And airgun shooters tend to sight in at much shorter distances, which uses up more of the available adjustment. But I think there might be more to it.
Whenever I shoot a springer, my scope hairs jump down after the trigger breaks. PB's jump up. In a powder burner, the recoil sends the shot up a significant amount. You can see this on a long barreled revolver. Set it upside down on a table on its sights, and the barrel is not parallel with the table. The front sight is significantly taller than the rears, in order to account for this change of impact by recoil. Shoot a heavier bullet, and the POI goes up even more, because the bullet exits later; thus, the bore is pointing higher due to recoil.
In a springer, the barrel moves down before the pellet exits the bore. This is partly cancelled out by the barrel rising during the piston's initial release, but not completely. Else the cross-hairs wouldn't shift so far down when you fired it.
I'm inclined to think that when your cross hairs are on the target, the bore must point above the target in most springers. After the piston slams home, the pellet accelerates. And the bore moves down. Then the pellet exits the bore when the bore axis crosses the target and scope hairs are below. Opposite to the situation in the pb revolver, in which the bore must necessarily point below the target axis the moment the trigger breaks.
You could say that a pb revolver needs anti-anti-drooper sights. PB rifles aren't affected as much due to heavier stocks and much higher velocities, plus the fact they are generally sighted in at longer ranges than revolvers. But springers are relatively unaffected by recoil or even affected the other direction, making it relatively normal for them to need droop compensation.