Discovery still shooting low.

Discovery still shooting low.

Joined: February 13th, 2006, 4:53 pm

August 19th, 2009, 10:09 pm #1

On my new Disco. I had to almost max out the height of the rear sight to get it to shoot somewhat on target, other wise it would simply shoot low. Been reading here about how the barrel band pinches the barrel towards the air tube and sure enough you can almost see it doing that and confirmed it with some feeler gauges. Barrel was touching, or almost touching, the filler cap. When I loosen the band the barrel does tip up. So I shimmed the band with aluminum can shims as suggested by a poster (Mike T.?). Put 2 above the air tube and 2 below the barrel. There is now more of a gap between the barrel and air tube towards the muzzle,and the barrel is not touching the filler cap, but floating just a hair above it. So I take it out to shoot without lowering the rear sight from its already very high setting, and the darn thing shoots even lower now! The exact opposite of what I would expect.

Help, any ideas?

Windage is fine.
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Joined: March 19th, 2006, 4:15 am

August 19th, 2009, 10:17 pm #2

on the barrel. when you pushed it up, you had to lower the barrel to get the proper sight picture, to level the sights. adjust the sights. john
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Joined: February 13th, 2006, 4:53 pm

August 19th, 2009, 10:36 pm #3

I see your point. The rear sight is mounted on the barrel sleeve, not the barrel and in raising the front sight I lowered the point of impact when aligned to the rear sight. Kind of like using the front sight adjustment on an AR-15 for example. Did not think their would be that much pivot between the barrel and barrel sleeve, I assumed it would be at the breech. Will try that out and get back.
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Joined: July 9th, 2001, 12:24 am

August 20th, 2009, 12:05 am #4

On my new Disco. I had to almost max out the height of the rear sight to get it to shoot somewhat on target, other wise it would simply shoot low. Been reading here about how the barrel band pinches the barrel towards the air tube and sure enough you can almost see it doing that and confirmed it with some feeler gauges. Barrel was touching, or almost touching, the filler cap. When I loosen the band the barrel does tip up. So I shimmed the band with aluminum can shims as suggested by a poster (Mike T.?). Put 2 above the air tube and 2 below the barrel. There is now more of a gap between the barrel and air tube towards the muzzle,and the barrel is not touching the filler cap, but floating just a hair above it. So I take it out to shoot without lowering the rear sight from its already very high setting, and the darn thing shoots even lower now! The exact opposite of what I would expect.

Help, any ideas?

Windage is fine.
To raise impact you can raise the rear or lower the front. I'd try filing some off the top. There's a limit of course to how much you can file off, but if you goof it up the replacement is cheap.

Doug Owen
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Joined: September 21st, 2007, 12:13 pm

August 20th, 2009, 12:52 am #5

On my new Disco. I had to almost max out the height of the rear sight to get it to shoot somewhat on target, other wise it would simply shoot low. Been reading here about how the barrel band pinches the barrel towards the air tube and sure enough you can almost see it doing that and confirmed it with some feeler gauges. Barrel was touching, or almost touching, the filler cap. When I loosen the band the barrel does tip up. So I shimmed the band with aluminum can shims as suggested by a poster (Mike T.?). Put 2 above the air tube and 2 below the barrel. There is now more of a gap between the barrel and air tube towards the muzzle,and the barrel is not touching the filler cap, but floating just a hair above it. So I take it out to shoot without lowering the rear sight from its already very high setting, and the darn thing shoots even lower now! The exact opposite of what I would expect.

Help, any ideas?

Windage is fine.
problem. The rear sight had to really be tweeked up to shoot where I pointed the gun. The problem solved itself when I modified the breech for a Williams/Sheridan peep sight.

Lowering the front sight on it's base might be problem,as the sight is milled on an arch to match the curvature of the sight base.
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Joined: March 19th, 2006, 4:15 am

August 20th, 2009, 1:15 am #6

I see your point. The rear sight is mounted on the barrel sleeve, not the barrel and in raising the front sight I lowered the point of impact when aligned to the rear sight. Kind of like using the front sight adjustment on an AR-15 for example. Did not think their would be that much pivot between the barrel and barrel sleeve, I assumed it would be at the breech. Will try that out and get back.
what i always found a challenge was to raise the front sight when the rear was fully depressed and the gun still shot high. john
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Joined: February 13th, 2006, 4:53 pm

August 20th, 2009, 2:44 am #7

To raise impact you can raise the rear or lower the front. I'd try filing some off the top. There's a limit of course to how much you can file off, but if you goof it up the replacement is cheap.

Doug Owen
Not possible on the front sight at least on my version of the Discovery. The fiber optic makes it undoable.
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Joined: February 13th, 2006, 4:53 pm

August 20th, 2009, 3:07 am #8

On my new Disco. I had to almost max out the height of the rear sight to get it to shoot somewhat on target, other wise it would simply shoot low. Been reading here about how the barrel band pinches the barrel towards the air tube and sure enough you can almost see it doing that and confirmed it with some feeler gauges. Barrel was touching, or almost touching, the filler cap. When I loosen the band the barrel does tip up. So I shimmed the band with aluminum can shims as suggested by a poster (Mike T.?). Put 2 above the air tube and 2 below the barrel. There is now more of a gap between the barrel and air tube towards the muzzle,and the barrel is not touching the filler cap, but floating just a hair above it. So I take it out to shoot without lowering the rear sight from its already very high setting, and the darn thing shoots even lower now! The exact opposite of what I would expect.

Help, any ideas?

Windage is fine.
Tried waunderin's suggestion and no luck. Lowered the rear sight to the max and all it did was lower the POI even lower. Worked the rear sight up gradually and all it did was slowly move the POI up. With the height of the rear sight maxed out it simply hits just below the target and I am back where I started from. What beats me is why does the shimming make the problem worse?! One thing I can try is using one shim, instead of two, above the air tube and below the barrel.

Another possibility is getting 2nd barrel band and shim that one too to match the original band.

I welcome any other suggestions.

The shimming did seem to make the shots more consistent, not sure about that yet, but it certainly worsened the low impact point.

I loosened the band and it seems the barrel and barrel band move, more or less, as one unit, so I am assuming the the front and rear sight are on the same plane. (?)
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Joined: April 27th, 2008, 10:28 pm

August 20th, 2009, 6:01 pm #9

remove the front sight, front sight mount and barrel band.

Place a straight edge along the top of the barrel and see if it's "straight."

My first Discovery back in May of 2008 had a barrel that was bent at the band mount point. Crosman sent another barrel and all was fine after that (I did drill the band to place additional set screws to keep the "squish" from happening.

Failing that, if you want to pay the shipping both ways, I'll be glad to have a look and fix it NC.

Mike T.

---+---

Drilled barrel band for extra support and to eliminate the opposing set-screws from jamming the barrel and airtube together:

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Joined: February 13th, 2006, 4:53 pm

August 20th, 2009, 6:14 pm #10

Will check the barrel for straightness. Thanks very much for the offer and suggestion. What gets me is why would the shimming make the problem worse!?
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