Whats your zero on your discovery?

[redneck]

I bought a discovery last winter, shot a couple tins of pellets through it at 25 yards and have been very happy with the accuracy.
This fall I've been using it for squirrels and started shooting it more at different distances. I'm a little disappointed in the rainbow like trajectory. If I zero at 25 yds I have to hold 1.5 mils over at 50 yds. I've tried different pellets and it doesn't seem to change much.
I figured that was what I was stuck with but I did some reading online and I'm finding guys claiming that they can zero at 40 yards and only be a half inch high at 25.
Thats what I was hoping for, and now I'm wondering if my gun isn't shooting slower than its supposed to? It will put a pellet all the way through a squirrel but its hard to make head shots when you have to be that accurate on your range estimation, and body shots don't put them down as fast as I'd like. I know its not going to be like a .22LR but I was hoping for a flatter trajectory than I'm getting. I don't have a chrony to do any testing, but I thought I'd find out if you guys with discoverys have similar results?

 

[jmorris]

but its hard to make head shots when you have to be that accurate on your range estimation,

If the distance difference between 25 yards and 50 yards is difficult for you to determine maybe it's time for a range finder.

 

[redneck]

25 to 50 yards isn't difficult, but its over 2 inches change in my POI. I just about have to change my holdover every 5 yards, and the squirrels don't stand around forever and while you figure a distance, adjust paralax etc.
I have done it successfully just about every time out this season, but I am reading that other people are claiming to have point and shoot trajectories out to 40 yards. I'm trying to determine if I have a problem with my gun or not.

 

[gspn]

but I am reading that other people are claiming to have point and shoot trajectories out to 40 yards. I'm trying to determine if I have a problem with my gun or not.

Are you shooting the same caliber as the people making those statements?

 

[jmorris]

There is a system called Maximum Point Blank Range that lets you pick a "window" that the bullet must stay inside, then with the BC of the projectile and speed it is going, you calculate the trajectory and place the "high" point in the arch as far out as possible and the furthest "low" point distance is your maximum point blank range. In other words with a 1" vital zone using MPBR the bullet path would never be more than a half inch high or low.

For example.

BC: .026
Velocity 800 fps
Vital zone (window of trajectory) 1.0"
Sight height 1.5"

Will give you a MPBR of 42 yards, if you zero at 38 yards.

-.2" @ 10 yds, 758.1 fps
.5" @20yds, 718.5 fps
.5" @ 30 yds, 680.8 fps
-.2 @ 40 yds, 644.8 fps
-1.8 @ 50 yds, 611.1 fps
-4.3 @ 60 yds, 597.2 fps

If you give me the BC of the pellet your using, the speed your rifle is pushing them and the distance from the centerline of the bore to the center of your optic, I will calculate it for what you have.

Edit I noticed the 20 and 30 yard being the same so I ran it again every 5 yards and it came up with .6" high at 25 yards not sure where the error is in the software but the data should still be pretty close.
FWIW this system assumes you shoot perfect 1 hole groups at the ranges in question as well. If you are shooting 1" groups and are artificially aiming a half inch high you can miss you POA by an inch.

 

[redneck]

Yes I am shooting a .22 and was comparing to others who were shooting the same. That is why I was starting to think I had a problem.

I don't have a chrony so I can't use ballistic software other than to guess. I was shooting JSB diablo exact jumbos, which seems to be a popular pellet for this gun.

The trajectories listed above were what I would like to have. Mine was literally hitting 2 inches low at 40 yards with a 25yd zero. So to keep inside a 1 inch circle, assuming a half inch group on my part I was having to adjust holdover every 5 yards more or less.

The good news is I shot about 100 rounds through the gun, tried 4 different types of pellets this afternoon. Got similar results in drop with crosman premier hollow point, crosman premier ultra dome, the jsb diablos, and gamo predators. Then all of a sudden the gun woke up. I shot a tank at 25 yards with about a half inch group with the premier hollow points, recharged the gun, set up at 40 yards and it was within a 1/4 inch with no holdover for the whole tank, kept about 3/4 inch group.

So I went back to my spot and a nice big fox squirrel came out at about 30 yards and it dropped him like a lazer. Much bigger exit wound than before. I guess at this point I'm going to assume it had some dirt in it or something. It seems to be shooting much better, we'll see if it lasts or not.

 

[Crawfish1]

Which pellets did you shoot last for the 3/4" group. Those sound like a winner for your gun.

If you shot the full tank with no drop something is wrong with your gun as it is not moderated. Unless you or someone else did a aftermarket mod. I would suspect 1.5 mil going from 25 to 50 yards would be average for most pellets as far as drop is concerned. In .22 I know I hold over 6 to 9 mils at 100 yards depending on which grain pellet I'm shooting. Not disco numbers but should hold a similar pattern of drop for a generic reference.

 

[jmorris]

I guess you could try the 38 yard zero and see what it does.

I think crawfish meant regulated as "moderated" in airgun language means suppressed.

Using the same input data from above but zeroed @ 25 yds gives

-.4 @ 10 yds
.0 @ 20 yds
-.2 @ 30 yds
-1.2 @ 40 yds

The JSB exact jumbos should be around a .030-.034 BC but with the extra weight your disco may not be pushing them fast enough to make a flatter trajectory.

 

[Crawfish1]

Yep that's what I meant. Multitasking whilst typing has never been a strong point of mine.

 

[redneck]

When I say I shot a tank, I mean I shot it down to 1200psi or so. I never shoot it out of the green on the gauge because then it does start dropping sporadically.

The premier hollow points were the last I shot that got the good group. The gun gets similar groups with the diablo jumbos as well, maybe a little better at 25 yards. Really not sure whats going on other than the gun must have had something sticking in the valve or something, as the premiers were the first thing I tried after the diablos this morning. Then I went to the gamos, then the ultra mags, then some more diablos and finally back to the premiers. Had the severe drop with all of them until the last round with the premiers.

 

[Crawfish1]

Well that's good news.

Crosman supports workers here and are affordable. Win , Win.


Like they say if it ain't broke don't fix it. Just enjoy it!