Umarex How does this barrel crown look?

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The BB Bandito

The BB Bandito

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Oct 7, 2024
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I used my bore scope to get a video of the crown in my rifle. I also included a picture of the worst spot. I’m curious what everyone’s thoughts are?


EDIT: thanks everyone for the feedback. I def learned some stuff.

Last night I tore everything down on the gun to replace the poppet valve. While I had everything apart I checked the seals, pulled the barrel, and inspected O-rings. Everything looked good and nothing was loose.

The poppet valve did have some discoloration on the stem. I’m assuming from heat or friction. It didn’t look pitted just discolored. It also had some dust/dirt on the valve seat nothing crazy but I cleaned everything up.

I replaced the valve then proceeded to live and tighten everything while assembling it.

Shot it today and the groups are back to being pretty tight. <.5” @25yds which is plenty for my squirrel problem. I’m guessing that the poppet wasn’t seating consistently each time. I’m guessing the timing and pressure curve from inconsistent sealing potentially lead to a harmonics shift throwing off some shots.



IMG_6875.jpeg
 
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Keeping in mind that the image (and the tooling marks) are greatly magnified and are making things look worse.

Best I can tell, the slight "chatter" from the chamfering tool looks even and consistent all around the bore.

If you're super-tuning a competition rifle (or just messing around because you want to 😉) you could (using a light touch) polish the crown a bit.

If the crown is not (obviously) causing a problem I'd leave well enough alone... if it's not broke, don't fix it!

Cheers!
 
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The BB Bandito said:
Ahh ok so where they terminate is the crown. I didn’t know that. I can update the video.
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Anything not in contact with the lands/grooves is just extraneous machining. For clearance or decoration or whatever.

Where the projectile looses contact with the bore, as it exits, is the Crown. That's the important bit.
 
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Vetmx said:
There are two electronic devices that can get a man in trouble with an airgun. A chronograph and a bore scope. Everything looks fine.
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You hit the nail on the head ! If it shoots well enough to do what you want , don't fool with it ( unless you have a good 'smith on retainer, like I do :LOL: )!
 
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Vana2 said:
If you're super-tuning a competition rifle (or just messing around because you want to 😉) you could (using a light touch) polish the crown a bit.

If the crown is not (obviously) causing a problem I'd leave well enough alone... if it's not broke, don't fix it!

Cheers!
Click to expand...
I’m having accuracy issues. The pellets aren’t grouping tight. They’re currently grouping around 1” @25yds. Shooting the same pellets that we’re grouping 3/8” @25yds. I’m trying to eliminate different things. It’s getting pretty frustrating knowing it can shoot tight groups but now it’s not. I’ve cleaned the gun, tighten everything I know to tight, scope is locked in, environmentals aren’t changing outside, maintaining the same tank pressure when shooting. Idk what’s going on man. I don’t even have the confidence to shoot at another squirrel right now.
 
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Contndr35BB said:
You hit the nail on the head ! If it shoots well enough to do what you want , don't fool with it ( unless you have a good 'smith on retainer, like I do :LOL: )!
Click to expand...
I agree with this statement 100% but it’s not shooting good. Hence all the diagnostic stuff. See the above comment for a rundown of what I’ve done. Unless anyone in here considers 1” @25yds good
 
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Have you Bronze Brush SCRUBBED the Bore ?
If barrel once shot well & does not now .... There it likely is ... Lead fouled someplace in bore.
* Ideal way to see lead fouling with a bore scope is NOT using the 90* mirror, but letting camera see bounce light in full radius of bore. lead fouling will look like a water spot sorta image ;)
 
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The BB Bandito said:
I agree with this statement 100% but it’s not shooting good. Hence all the diagnostic stuff. See the above comment for a rundown of what I’ve done. Unless anyone in here considers 1” @25yds good
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A crown just doesn’t mysteriously go bad. Now if you cleaned the barrel from the bore with a metal rod, maybe. But even then it would take some recklessness to damage the crown. It can be very frustrating when groups open up and you cant figure out why. All I can say is wait until tomorrow and try a different tin of pellets.
 
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The BB Bandito said:
I’m having accuracy issues. The pellets aren’t grouping tight. They’re currently grouping around 1” @25yds. Shooting the same pellets that we’re grouping 3/8” @25yds. I’m trying to eliminate different things. It’s getting pretty frustrating knowing it can shoot tight groups but now it’s not. I’ve cleaned the gun, tighten everything I know to tight, scope is locked in, environmentals aren’t changing outside, maintaining the same tank pressure when shooting. Idk what’s going on man. I don’t even have the confidence to shoot at another squirrel right now.
Click to expand...
Sounds like the airgun has been thoroughly gone over. Maybe try another scope?

Seen a scope that was adjusted too close to its maximum, got bumped and the erector tube started "floating" causing the groups to open up.

Have you checked/confirmed that the parallax was properly adjusted? That could easily throw the POI off.

Good luck!
 
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Motorhead said:
Yea as we are finding out with the JSB / AA .177 10.3's :mad::mad::mad::mad: The new packaging is also a new pellet / die that is sorta close to the original in looks, but sure does not shoot like them :mad::mad::mad::mad:
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I have a supply of JSB and AA 10.3's, and I don't believe that I have encountered these new and different pellets. Is there an easy way to differentiate these from the old ones? You mentioned "new packaging". Is it obviously different? Sounds like I might be in for some pellet testing if these new ones don't perform as the old.
 
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