Donation

All Springer/NP/PCP Air Gun Discussion General > Optics, Range estimation & related subjects

barrel droop.....does it even exist?

(1/4) > >>

Joey:
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.

Eddie_E:
Well, the biggest offender recently re-designed a rifle that has been in production for 40 years to accept droop shims right below the breach seal. That sort of confirms it can be caused breach seal thickness and lockup wedge position as well.(break barrel). Scope height over barrel usually resolves itself beyond 14 yards.

 One guy I shoot with occasionally had his hand slip off a partially cocked Benji that previously had no issues and it shifted the poi up over 2" until he changed the breech seal.

Hoosier Daddy:
Here is what I believe

Airgun 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"

Bentong:
yup...we all tend to droop over time. Compensation is the key.

wolverine:
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.

Navigation

[0] Message Index

[#] Next page